Biology 102

Chapter 1: Food Choices and Human Health

• Phyto chemicals - important part of fruit and vegetables

  • Phyto → refers to plants

  • The ways chemicals react with each other

Ex. Fibreheanu

• Nutrition - the study of how food nourishes the body

• Food - any substance the body can take in and assimilate (broken down and absorbed)

  • A source of nutrients

  • Used to enable the body to stay alive and grow

• Nutrients - components of food required for the body’s functioning

  • Roles

    • Provide energy

    • Building material

    • Maintenance & repair

    • Support growth

• Essential nutrients - nutrients that the body either cannot make, or cannot make fast enough, from other raw materials

  • nutrients must be obtained from food → if not, deficiencies will occur

    • Water

    • Form of carbohydrate

    • Some lipids

    • Some parts of protein

    • Vitamins

    • Minerals

  • In most foods → without fancy diet

• Diet - foods a person usually eats and drinks

  • Incorrectly suggests calorie restriction

• Optimal food - food that supports the growth and maintenance of muscle, bones, skin, and sufficient blood

  • food should supply sufficient energy, water, carbohydrates, fat, protein, vitamins, and minerals

• Dietary supplements - pills, liquids, or powders that contain purified nutrients or other ingredients

  • CANNOT be used in place of food → food offers more than just six basic nutrients

• Elemental diet - diets composed of purified ingredients of known chemical composition

  • Intended to supply all essential nutrients to people who cannot eat foods

  • No longer any natural interaction between chemicals → lose benefits

  • Recently been marketed as “meal replacers” or “insurance” against malnutrition

    • Do not support optimal growth and health

    • Can lead to medical complications

  • Digestive tract is a dynamic system (adaptable, changeable, different every day) that responds to the food it receives → including sight, aroma, and taste of food

    • When a person is fed through a vein, the digestive organs atrophy (waste away, shrinks down) → lack of digestive tract stimulation, which may weaken the body’s defences against certain infections

• Supplements - pills, liquids, or powders that contain purified nutrients or other ingredients

  • Cannot be used in place of food

    • Food offers more than just the six basic nutrients

  Foods are chemically complex

• Non nutrients - compounds other than the six nutrients present in food that have biological activity in the body

  • Include phytochemicals

    • Compounds in plant-derived foods that have biological activity in the body

      → Confer colour, taste, etc. on foods

    • Many are thought to affect health by reducing disease

  Well chosen array of foods will prevent malnutrition

• Malnutrition - nutrient deficiencies, nutrient imbalances, nutrient excesses

• Under nutrition - nutrient or deficiencies

• Over nutrition - nutrient or energy excess

Two common lifestyle habits have a stronger influence on long-term health than dietary choices:

1. Smoking & other tobacco use

2. Excessive alcohol consumption

Other factors that affect health besides diet:

• Tobacco use

• Alcohol use

• Substance abuse

• Physical activity

• Sleep

• Stress

• Conditions at home and work

Role of Nutritious Diet in Disease Prevention:

• Genetics & diet

• Lifestyle factors

• Type of disease

Genetics and Individuality:

• Genetics and nutrition have varying affects on diseases

  • Some are purely hereditary

  • Some diseases are often the result of nutrition-based factors

  • Some are influenced by both genetics and nutrition

• Nutritional genomics - how nutrition affects the activity of genes and how genes affect the activity of nutrients

  • Holds the promise of more precisely determining an individual’s nutrient needs, fighting disease etc.

  • Diet alters expression of genetic information

• Nutrigenomics - determination how nutrition affects health and the development of chronic diseases

  • Has proved challenging because humans are not good experimental subjects for most molecular genetic studies

  • Each human has a unique genotype and it is difficult to control for environmental influences

    → both of these variables can be controlled in studies with laboratory animals

  • Research is conducted in yeast, fruit flies, and worms along with rats and mice

    • Rats and mice are useful for genetic studies because of the relatively short generation times and planned breeding can be done to test genetic hypotheses

• Organic - contains carbon and was made by a biological organism

Organic Nutrients (contain carbon)

• Water (no carbon, but still organic)

• Carbohydrate

• Fat

• Protein

• Vitamins → need in small amounts (regulatory factor)

• Minerals (complex) → need in small amounts (regulatory factor)

Food and the human body are composed of the same materials:

• Water (60%-70%)

• Carbs, fats, and protein

  • Energy yielding

• Vitamins and minerals

  • Regulatory factors

The Human Body & Its Food:

• Energy - the capacity to do work

  • The energy that fuels the human body comes indirectly from the sun via plants

  • Food energy is measured in calories

• Calories - units of energy

  • Kilocalorie = kcalorie = calorie

  • Used to measure energy in food

  • Amount of heat energy needed to raise the temperature of 1 kilogram of water 1C

Calorie Values of Energy Nutirents:

Carbohydrate = 4 cal/g

Fat (lipid) = 9 cal/g

Protein = 4 cal/g

* Alcohol = 7 cal/g → NOT classified as a nutrient because it interferes with growth, maintenance, and repair of body tissues

Why people choose foods:

• Positive associations

• Region of the country

• Social pressure

• Values and beliefs

• Weight

• Nutritional value

→ Our genetic makeup will influence the foods we eat

• Each person has a different combination which makes some people sensitive and other numb to certain tastes

  • Our tastebuds on our tongue are like fingerprints

Eating offers both physical and emotional comfort:

• The intestine releases hormones in response to food

  • These hormones send messages to the brain that bring the eater a feeling of satisfaction

Reading Nutrition News:

Educated consumers of nutrition information keeps the following in mind:

• The study being described should be published in a peer-reviewed journal

• The news reporter should state the purpose of the study & describe the research methods

  • Should note the limitations of the study

Science of Nutrition:

What to look for in a research article:

• Abstract

• Introduction

• Review of literature

• Methodology

• Results

• Conclusions

• References

Examples of research design:

• Epidemioogical

• Case/control studies

• Lab intervention

→ cause and effect

• Whole organism lab studies

• Cellular/molecular level lab research

Chapter 2: Nutritional Tools, Standards and Guidelines

• Nutrient recommendations - sets of yardsticks used as standards for measuring healthy people’s energy & nutrient intakes

  • Nutrition experts use the recommendations to assess intakes & to offer advice on amounts to consume

    • Updated regularly

    • Optimum levels

    • Goal = average intake

    • Set to cover majority (age, gender etc)

    • Applies to healthy people’s

Preventing Chronic Diseases:

• The DRI committee takes into account chronic disease prevention, wherever appropriate

  • Ex → the committee set lifelong intake goals for calcium at levels believe to lessen the likelihood of osteoporosis-related fractures in the later years

    • “Bone porous”

      → devastating, pain crippling fractures

      → 20% die >25 million affected

      → no symptoms until it’s too late

      → bones holes and fragile

Facilitating Nutrition Research and Policy:

• Nutrient requirements for given life stages and ender groups that researchers and nutrition policymakers use in their work

• Publish health officials may also use them to assess nutrient intakes a of populations and make recommendations

Establishing Safety Guidelines:

• Identify potentially hazardous levels o nutrient intake

• Indispensable to consumers who take supplements or consume foods or beverages to which vitamins or minerals have been added

• Public health officials rely on UL values to set safe upper limits for nutrients added to our food and water supply

Upper Limits:

• People’s tolerances for high doses vary

  • Caution is in order when nutrient intakes approach UL values

    • This does not imply that it is safe to consume

  • Above tolerability upper intake level could lead to the danger of toxicity

Health Canada’s Message to Consumers:

• Health Canada makes applying its Food Guide easier through a graphic that depicts the highlights of the Food Guide

  • The rainbow intended to emphasize vegetable & fruit consumption

Understanding the DRI Intake Recommendations:

• Within your own age & gender group he committee advises adjusting nutrient intakes in special circumstances that may increase or decrease nutrient needs

  • Such as illness, smoking, or vegetarianism

Limitations:

• Doesn’t consider CHO, fat, saturated fat, protein calorie content, nutrition density

• Doesn’t guarantee intake of adequate nutrients - could still be malnourished

• Does not limit calories

• Indicates fat/sugars wth symbols but doesn’t specify foods with high levels

Nutrient Recommendations:

• Standards in the U.S and Canada are the Dietary Reference Intakes (DRI))

  • A set of four lists of values for measuring the intakes of healthy people

    • Estimated Average Requirements (EAR)

    • Recommended Dietary Allowances (RDA) * need to know

    • Adequate Intakes (AI) * need to know

    • Tolerable Upper Intake Levels (UL) * need to know

• Daily values (DV) - nutrient standards used on food labels, in grocery stores, and on some restaurant menus. The DV comparisons among foods with regard to their nutrient contents.

How Committee Establishes DRI Values:

• Often balance study

  • Compare nutrient intake vs excretion of excess

• Determines requirement of average person

• Levels cover majority of population without being excessive for some

• Values set for nutrient requirements - generous

• Those set for energy (cal) requirements - limited

Setting Recommended Intake Values:

• RDA

  • Based on solid experimental evidence and reliable observation

• AI

  • Also scientifically based as possible, but setting them requires some educated guesses

  • Established whenever scientific evidence is insufficient to generate an RDA

Nutrient Recommendations

• Another set of nutrient standards is practical for the person striving to make wise choices among packaged foods

  • Daily values

    • Nutrient standards that are printed on food labels

    • Based on nutrient and energy recommendations for a general 2000 calorie diet

Why Are DV Used on Labels?

• DRI values vary from group to group

• On a label, one set of values use apply to everyone

  • DV reflects the needs of an “average” person

    • Based on a 2000-2500 calorie per day intake

• DV are ideal for allowing comparison among foods

  • The purpose of the %DV is to show whether the food has a ‘lot’ or a ‘little’ of a nutrient in a stated amount of food

• Because the DVs apply to al people, they are much less useful as nutrient intake goals for individuals

Nutrition Facts Panel Must:

• List ingredients

• Provide details about a food’s nutrient composition

* Each gram of fat has 9 calories *

* 1g of carbohydrate = 4 calories *

Chapter 3: The Remarkable Body

Cells: Basic Units of Life

• Cells require nutrients

  • Each of the body’s cells is a self-contained, living entity

    • However, each cell depends on the rest to supply its needs

      → these needs include energy, oxygen, water, building blocks, intros systems, and especially the essential nutrients

The Body’s Cells:

• All living things including cells die

  • Some skin cells and red blood cells must replenish themselves every 10 to 120 days

  • Cells lining the digestive tract replace themselves every three days

• Many muscle cells reproduce only once every few years

  • Liver cells have the ability to reproduce quickly and do so whenever repairs are necessary

  • Certain brain cells do not reproduce at all

• Nucleus

• DNA → RNA → protein

• Genes

  • Have the ability to make protein

  • DNA → protein

• Protein

  • Each is slightly different

• Living cell

• Living tissue

Genetic and Nutrition:

• DNA is what you receive from your father and mother

• Many genes have changes very little form thousands of centuries ago

• There is no guarantee that a diet chosen form today’s food will meet the needs of your ‘ancient’ body

• Unlike you ancestors you must learn how to select food to meet your body’s needs

The Working of Genes:

• Each cell contains a complete set of genes

  • Different ones activate in different types of cells

  • Different proteins (enzyme) will be built and function in different cell types

    • In some body’s fat cells, the genes for making enzymes in hormones and enzymes involved in appetite and energy balance

Metabolism:

Metabolism = catabolism and anabolism

• The sum of all building up reactions and breaking down reactions chemical reactions that occur in living cells require enzymes

Chemical reaction in biology → A + B = C (enzymes)

• Not a spontaneous reaction

• Enzymes are usually globular structures which act on much smaller substrates

• Each protein has a unique shape

• One the surface of each enzyme is one small area called the active site which is the key to the enzymes specificity

• Enzymes may also depend on “cofactors” that are essential for activity

  • Special substrates that bind temporarily to a site on the enzyme

  • The enzyme itself is not changed in the chemical reactions it catalyzes - the cofactor will be

• Cofactor

  • Used interchangeably with ‘regulatory factor’

• Energy stores in organic molecules is found in the chemical bonds (100s)

  • If these molecules were to release all their energy at the same time a large amount of energy would be lost in the form of heat = spontaneous combustion

• Cells break down (or build up) organic molecules in “steps” called metabolic pathways

Cells, Tissues, and Organ Systems:

• Cells are organized into tissues

  • Perform specialized tasks

• Tissues are grouped together to form organs

• Several related organs working tougher comprise a body system

  • Cardiovascular

    • To move nutrients to the tissues

  • Endocrine

    • Regulatory system

  • Digestive

    • Absorption of nutrients

  • Excretory

    • Removal of wastes

  • Storage

    • Long term and short term energy needs

The Body Fluids and the Circulatory System:

• Body fluids supply tissues with energy, oxygen, and nutrients, including water

  • Fluids circulate to pick up fresh supplies ad deliver waste to points of disposal

• Every cell draws oxygen an nutrients from those fluids

• Every cell releases carbon dioxide and other waste products into other body fluids

Cardio Vascular System:

• Carry energy, O2, nutrients, H20 to cells, remove waste

• Blood in arteries, veins, capillaries

• Lymph in lymphatic vessels

The body’s main fluids are:

• Blood

  • the fluid of the cardiovascular system

    • Compsoed of water, red and white blood cells, othe foreign particles, nutrients, oxygen

  • Blood travels within arteries, veins, and capillaries, as well as within the heart chambers

  • Circulating within these vessels is the plasma of the blood

• Lymph

  • The fluid that moves from the blood stream into tissue spaces and then travels in it own vessels

    • Which eventually drain back into the blood stream

    • Fat (lipids) travels in lymphatic vessels → cannot travel in blood (doesn’t dissolve) → hydrophobic

      → pick up the most fats from the intestine then transport the fats to the blood (requires some change first)

• Extracellular fluid

  • The fluid surrounding the cells

    • Derived from blood in capillaries

      → flows around the outside of cells, permitting exchange of materials

• Intracellular fluid

  • Fluid inside cells

    • Medium in which all chemical reactions take place

    • It’s pressure helps the cells to hold their shape

    • Is drawn from the extracellular fluid

• Lungs

  • Where blood pick up oxygen and releases CO2

• Digestive system

  • As blood passes through the digestive system, blood relievers oxygen and picks up most nutrients from the intestine → other than fats and their relatives

    • These nutrients will be distributed to other body cells

• Liver

  • All blood leaving the digestive system is routed directly to the liver

  • Filters blood

  • Removes and processes nutrients

  • Manufactures materials for export to other parts of the body

  • Destroys toxins or stores them to keep them out of circulation

• Kidneys

  • Waste is filtered from the blood, urine is made and released to the bladder for exertion from the body

  • Ample fluid intake is needed to ensue efficient circulation of fluid to all your cells

    • Drinking sufficient water to replace the water lost each

    • Cardiovascular fitness is also essential

• Healthy red blood cells

  • Body replaces constantly

  • Essential

  • Process requires many essential nutrients therefore making blood

    • Very sensitive to malnutrition

  • Often serves as an indicator of disorders caused by dietary deficiencies or imbalances of vitamins or minerals

• Hormones

  • Chemicals secreted by glands in response to conditions in the body that require regulation

  • Serve as chemical messengers

  • Act on organs to maintain constant conditions

  • Each gland monitors a condition and produces one or more hormones to regulate it

  • Each hormone acts as a messenger that stimulates various organs to take appropriate action

  • Chemicals that have some effect on a cell

Energy Balance and Healthy Body Weight:

• Leptin → hormone

  • suppresses appetite

• Ghrelin

  • stimulates eating

  • produced by lack of sleep

The Hormonal & Nervous System:

• A hormone produced by fat tissue (leptin) informs the brain about the degree of body fatness & helps to regulate appetite

• Hormones also regulate the menstrual cycle in women, affecting appetite (pregnancy)

• Hormones maybe partially responsible for the loss of appetite that sick people experience (cache in cancer patients)

• Stress hormones will affect appetite → suppress hunger, digestions, and absorption

1. to signal hunger the digestive tract sends messages to the hypothalamus (in the brain) via hormones and nerves

2. the signals stimulate the stomach to intensify its contractions and secretions

   • causing hunger pains, sensations of hunger, and appetite are perceived by the brain’s cortex

3. when the brain’s cortex perceives hunger sensations you want to eat, but the conscious mind can override such signals

   • a person can choose to delay eating despite hunger or to eat when hunger is absent

Fight or Flight vs Rest and Digest:

• the stress response

• when danger is detected nerves release neurotransmitters

  • chemicals that facilitate communication between nerve cells

• when danger is detected glands release epinephrine and norepinephrine

  • the major hormones that elicits the stress response

Stress Response - Effect on how we eat:

• the release of neurotransmitters and hormones speeds up metabolism

  • the sum of all physical and chemical changes taking place in living cells

Result of an increase in metabolism:

• pupils of eyes widen

• muscles tense up

• breathing quickens and deepens

• heart rate and blood pressure increase

• the liver releases glucose from its stores

• fat cells release fat

• digestive system shuts down

→ in ancient times, stress often involved physical danger

• the response was violent physical exertion

→ in the modern world, stress is seldom physical

• but the body reacts the same way → leading to the number one chronic disease of the 21st century

→ the major enemy of today = atherosclerosis

• the accumulation of fat and other constituents in the arteries and stresses that strain the heart often lead to heart attacks

  • especially when a body accustomed to under exertion experiences sudden high blood pressure → this is why daily exercise is a part of a healthy lifestyle

What happens to the food we eat?

→ undergoes three processes:

1. digestion

2. absorption

3. elimination

→ these processes occur in the gastrointestinal tract (GI) - food processor

The digestive tract is a flexible muscular tube extending from the mouth to the anus

• the human body surrounds this digestive canal when you swallow something it is not inside your body until you absorb it

• many thing pass through the digestive tract without being absorbed

Mechanical digestion begins in the mouth

• chewing shred food into pieces small enough to swallow

  • adds water in the form of saliva

    • softens rough/sharp foods

    • saliva moistens and coats food making it slippery

• chewing releases nutrients trapped inside indigestible skins

  • corn kernels

  • once a food is mashed and moistened, there is no advantage to additional chewing

• the stomach and intestines liquefy foods

  • peristalsis

    • wave-like muscular squeezing

    • begins at the esophagus and pushed food along the digestive tract

Mechanical aspect of digestion:

• the stomach stores food in its upper portion

  • little by little food is squeezed into its lower portion and released to the small intestine

• at the base of the esophagus is a sphincter muscle

  • this prevents reflux of stomach contents into the esophagus

Rate of stomach emptying:

• 2-6 hours depending upon composition of meal

• high CHO content = fastest

• high protein = fast

• high fat = slowest

• release hormones that slow GI motility

• the digestive tract is protected from acid by mucus

• large intestine = colon

  • digestion and absorption are nearly complete by the time food arrives here

  • the colon primarily reabsorbs water and absorbs minerals

  • fiber and undigested materials make up the feces

• transit from mouth to rectum takes from 1 to 3 days

Chemical Digestion:

• digestion begins in the mouth

  • an enzyme in saliva begins the digestion of fat

  • saliva helps maintain the teeth

    • it washes away food particles that would otherwise promote tooth decay

    • it neutralizes acids produced by oral bacteria

• continues to the stomach

  • chyme - the fluid resulting from the action, both mechanical and chemical breakdown, of the stomach upon a meal

• protein digestion begins in the stomach

  • the stomach releases gastric juice

    • a mixture of water, enzymes, HCI

      → the acid is needed to activate a protein digesting enzyme

    • protein digestion is the stomach’s main function

Most digestion and absorption occur in the small intestine

• the hormonal messenger stimulate the gall bladder to release bile into the intestine

  • bile - produced by the liver and is an emulsifier (a compound that attracts fats into water)

• hormonal messengers stimulate the pancreas to release pancreatic juice

  • containing both enzymes and bicarbonate

    • bicarbonate neutralizes stomach acid

• as pancreatic and intestinal enzymes break down nutrients, small pieces are released into intestinal fluids

• eventually, pieces are small enough such that nutrients can be absorbed

• at this point, only water, fibre, and some mineral remain in the digestive tract

Absorption and transportation of nutrient:

• absorption in the intestine is selective

  • Ex. when calcium is in short supply its absorption increases

• Absorption

  • villi and microvilli increased surface area for absorption

    • occurs in small intestines (nutrients)

    • and large intestines (H20, vitamins, and minerals)

• the organs of the digestive tract analyze the diet nutrient content and deliver juice and enzymes appropriate for giesting those nutrients

• each villus had its own capillary network and lymph vessel — nutrients that move across the walls are immediately moving through body fluids

• the digestive system cells are sensitive to energy levels, nutrients or fibre

• undernutrition - the absorptive surface will shrink

  • 1/10 normal — very hard to absorb limited food supply

• no fibre - no “bulk” for the muscles to push against

  • muscles become weak

Malnutrition is self perpetuating → impaired digestion makes malnutrition worse

• malabsorption - used to describe the inability to absorb nutrients through the gut lining into the bloodstream

  • not a disease by itself, but rather the result of some other condition that is present

  • the small intestine is typically involved in malabsorption, since the majority of nutrients are absorbed there

  • may affect one or more of the many nutrients present in the diet

    • fat, protein, carbohydrate, vitamins, and minerals

  • there are over 100 different condition that can lead to problems in absorbing food (most of which are rare)

  • the degree of malabsorption depends on the type of underlying condition and the extent to which it has affected the gut

  • some of the more common malabsorption syndromes are due to bacterial/parasitic infections

    • crohn’s disease

    • celiac disease

    • ulcerative disease

    • liver disease (cirrhosis, hepatitis, gallstones)

    • cystic fibrosis

    • lactose intolerance

    • chronic pancreatitis

  • may occur when certain minerals present in the digestive tract in large amounts prevent adequate absorption of other minerals that are present in relatively small amounts

    • calcium

    • copper

    • iron

    • magnesium

    • manganese

    • zinc

Excretory System:

• waste must be eliminated

  • CO2 is eliminated via the lungs where it is exchanged for O2

  • other wastes are pulled out of the blood by the liver

    • the liver processes these wastes and either:

      • send them to the digestive tract with bile, to leave the body with feces

      • prepares them to be sent to the kidneys for disposal in the urine

• kidneys (waste and water removal specialists)

  • filters blood

    • waste dissolved in water is collected by kidney’s nephrons

      → the functional units of kidneys

      → waste becomes concentrated in the urine which travels through tubes to the urinary bladder

  • due to their role in toxin removal, whatever is good for the kidneys is good for the body

    • strong cardiovascular system

    • abundant supply of water

    • energy

    • vitamins and minerals

    • exercise

Immune System:

• skin presents a physical barrier to infection

• the body’s cavities are lined with membranes that resist penetration by unwanted substances and microbes

  • bacteria, viruses, and other organisms invisible to the naked eye

  • these linings are sensitive to vitamin and other nutrient deficiencies

  • health-care providers inspect both skin and the mouth to detect signs of malnutrition

→ the cellular immune system

• white blood cells

• phagocytes, b cells, t cells

  • seek out and destroy foreign invaders and unhealthy cells

Impaired Immunity:

• deficiency of any single nutrient can significantly impair immunity

• nutrient deficiency is by far the most common cause for poor immune function

• many people are overfed but undernourished

The body’s energy balance:

• when more food energy is consumed than needed, excess fat accumulates in the fat cells of the body’s adipose tissue

• daily energy balance — change in energy stores = energy in - energy out

  • energy input should equal energy output

Storage:

1. excess intake of calories

   • fat (long-term)

   • glycogen (short-term) → liver glycogen used (3-6 hours)

   • excess energy stored in fat cells or muscle cells

Midterm #1:

• food - any substance that the body can take in and assimilate that will enable it to stay alive and to grow

• nutrition - the study of nutrition and other biologically active compounds in food and in the body

  • sometimes also the study of human behaviours related to food

• diet - the foods (and beverages) a person usually eats or drinks

• nutrients - components of food that are indispensable to the body’s functioning

  • provide energy

  • serve as building material

  • help maintain or repair body parts

  • support growth

  • nutrients include water, carbohydrates, fat, protein, vitamins, and minerals

• malnutrition - any condition caused by excess or deficient food energy or nutrient intake or by an imbalance of nutrients

  • deficiencies are classed as forms of undernutrition; nutrient or energy excesses are classed as forms of overnutrition

• chronic diseases - long-duration degenerative diseases characterized by deterioration of the body organs

  • heart disease, cancer, diabetes

Genetics and Individuality:

• genetics and nutrition affect different diseases to varying degrees

  • anemia - blood condition in which red blood cells (oxygen carriers) are inadequate or impaired and cannot meet the oxygen demands of the body

    • purely hereditary → appears as a genetic disease unrelated to nutrition

  → nothing a person eats affects their chances of developing anemia, however, nutrition therapy may help ease its course

  • iron-deficiency anemia - most often results from undernutrition

• DNA - molecule that encodes genetic information in the structure

• genome - the full complement of genetic material in the chromosome of a cell

  • genomics - the study of genomes

• genes - units of a cell’s inheritance, made of chemical DNA

  • each gene directs the making of one or more proteins, which performs important tasks in the body

• nutritional genomics - the science of how nutrients affect the activities of genes and how genes affect the activities of nutrients

  • also called molecular nutrition or nutrigenomics

• energy - the capacity to do work

  • energy in food is chemical energy; it can be converted to mechanical, electrical, heat or other forms of energy in the body

  • food energy is measured in calories

Nutrients in Food:

• organic - carbon containing

  • four of the six classes of nutrients are organic

    1. carbohydrate

    2. fat

    3. proteins

    4. vitamins

• energy-yielding nutrients - the nutrients the body can use for energy

  • may also supply building blocks for body structures

• essential nutrients - the nutrients the body cannot make for itself (or fast enough) from other raw materials

  • must be obtained from food to prevent deficiencies

• calories/kcalories - units of energy

  • unit used to measure the energy in foods is a kilocalorie

    • the amount of heat energy necessary to raise the temperature of a kilogram of water by 1 degree

    • 1 calorie/kcalorie = 4.2 kilojoules

• grams - units of mass

  • the mass of a cubic centimetre or millilitre of water and under defined conditions of temperature and pressure

→ the most energy rich nutrient is fat

• contains 9 calories in each gram

  • carbohydrate and protein each contain only 4 calories in a gram

Supplements:

• dietary supplements - pills, liquids, or powders that contain purified nutrients or other ingredients

• elemental diets - diets composed of purified ingredients of known chemical composition

  • intended to supply all essential nutrients to people who cannot each foods

• non nutrients - compounds other than the six nutrients that are present in foods and have biological activity in the body

  • phytochemicals - non nutrient compounds in plant-derived foods that have biological activity in the body

    • convey colour, taste, and other characteristics on foods

→ food conveys emotional satisfaction and hormonal stimuli that contribute to health

Food Choices:

• basic foods - foods that are generally considered to form the basis of a nutritious diet (also called whole foods)

  • milk/milk products

  • meats/fish/poultry

  • vegetables

  • fruits

  • grains

• enriched foods/fortified foods - foods in which nutrients have been added

  • if the starting material is a whole, basic food such as milk or whole grain → highly nutritious

  • if the starting material is a concentrated form of sugar or fat → may be less nutritious

• fast foods - restaurant foods that are available within after customers order them

  • hamburgers, french fries, milkshakes

  • may or may not meet nutritional needs

• functional foods - reflects the attempt to define as a group the foods known to possess nutrients or non nutrients that might lend production against diseases

  • however, all nutritious foods can support health in some way

• natural foods - term that has no legal definition but often is used to imply wholesomeness

• nutraceutical - used to describe a product that has been isolated from food, often sold in pill form and believed to have medicinal effects

• organic foods - goods grown without synthetic pesticides or fertilizers

  • in chemistry, all foods are made mostly made of organic compounds

• processed foods - foods subjected to any process, such as milling, alteration of texture, addition of additives, cooking, or others.

  • depending on the starting material and the process, a processed food may or may not be nutritious

• partitioned foods - foods composed of parts of whole foods such as butter, sugar, or corn oil

  • generally overused and provide few nutrients with many calories

• staple foods - foods used frequently or daily

  • rice and potatoes

Recognizing a Nutritious Diet:

• adequacy - the dietary characteristic of providing all the essential nutrients, fibre, and energy in amounts sufficient to maintain health and body weight

• balance - providing foods of a number of types in proportions to each other

  • foods rich in some nutrients do not replace foods that are rich in other nutrients

    • called proportionality

• calorie control - control of energy intake

  • a feature of a sound diet plan

• moderation - providing constituents within set limits, not to excess

• variety - providing a wide selection of foods

  • opposite of monotony

Factors That Drive Food Choice:

1. convenience

2. psychological

3. social

4. cultural

5. philosophical

→ weight and nutritional value assign a high priority to nutritional health

→ cultural traditions and social values revolve around food

Nutrient Recommendations:

• dietary reference intake (DRI) - reports containing a set of five lists of nutrient intake values for healthy people in Canada and the United States

  1. recommended dietary allowances (RDA) - nutrient intake goals for individuals

     • the average daily nutrient intake level that meets the needs of nearly all healthy people in a particular life stage

  2. adequate intakes (AI) - nutrient intake goals for individuals are set whenever scientific data are insufficient to allow establishment of RDA value

     • the recommended average daily nutrient intake level based on intakes of healthy people in a particular life stage and assumed to be accurate

  3. estimated average requirements (EAR) - the average daily nutrient intake estimated to meet the requirement of half of the healthy individuals

     • used in nutrition research and policymaking and the basis upon which RDA values are set

  4. chronic disease risk reduction (CDRR) - a new DRI category based on chronic disease risk

     • Ex. keeping the sodium intake below the CDRR is expected to reduce the risk of chronic disease for the otherwise healthy population

  5. tolerable intake levels (UL) - the average daily nutrient intake level that is likely to pose no risk of toxicity to almost all healthy individuals of a particular life stage

     • usual intake above this level may place an individual at risk of illness from nutrient toxicity

  6. acceptable macronutrient distribution ranges (AMDR) - values for carbohydrate, fat, and protein expressed as percentages of total daily caloric intake

     • ranges of intakes set for the energy-yielding nutrients that are sufficient to provide adequate total energy and nutrients while reducing the risk of chronic diseases

• daily values (DV) - nutrient reference standards used on food labels

  • allow comparison among foods with regard to their nutrient contents

• balance study - lab study in which a person is fed a controlled diet and the intake and excretion of a nutrient are measures

  • valid only for nutrients like calcium (chemical elements) that do not change while they are in the body

• requirement - the amount of a nutrient that will just prevent the development of specific deficiency signs

  • distinguished from the DRI recommended intake value, which is a generous allowance with a margin of safety

• estimated energy requirement (EER) - the average dietary energy intake predicted to maintain energy balance in a healthy sult of a certain age, gender, weight, height, and level of physical activity consistent with good health

Canada Food Guide:

• exchange system - a diet planning tool that organizes food with respect to their nutrient contents and calorie amounts

• discretionary calorie allowance - the balance of calories remaining in a person’s energy allowance after accounting for the number of calories needed to meet recommended nutrient intakes through consumption of nutrient-dense foods

  • people with this may choose to consume the following within the limits of allowance:

    1. extra servings of the nutrient-dense foods that make up the base of the diet

    2. fats from two sources

       • foods higher in naturally occurring fats

       • added fats

    3. added sugars

       • jams, colas, and honey

    4. alcohol (within limits)

    5. alternatively, a person wanting to lose weight might choose to omit the discretionary calories form the diet

       • this is a safe strategy

• healthy eating index - a dietary assessment tool that evaluates a diet’s adherence to the principles of the USAD food guide as well as the variety of foods the diet contains

The Body Cells:

• cells - the smallest units in which independent life can exist

  • all living things are single cells or organisms made of cells

• enzyme - any great number of working proteins that speed up a specific chemicals reaction, such as breaking the bonds of a nutrient, without undergoing change themselves

• fat cells - cells that specialize in the storage of fat and form fat tissue

  • also produce enzymes that metabolize fat and hormones involved in appetite and energy balance

• tissues - systems of cells working together to perform specialized tasks

  • muscles, nerves, blood, and bone

• organs - discrete structural units made of tissues that perform specific jobs

  • heart, liver, brain

• body system - a group of related organs that work together to perform a function

  • circulatory system, respiratory system, and nervous system

Cardiovascular System:

• blood - the fluid of the cardiovascular system

  • composed of water, red and white blood cells, other formed particles, nutrients, oxygen, and other constituents

  • carries nutrients from the intestine to the liver, which releases to them to the heart, which pumps them to the waiting body tissues

• lymph - the fluid that moves from the bloodstream into tissue spaces and then travels in its own vessels, which eventually drain back into the bloodstream

• arteries - blood vessels that carry blood containing fresh oxygen supplies from the heart to the tissues

• veins - blood vessels that carry blood, with the carbon dioxide it has collected, from the tissues back to the heart

• capillaries - minute, weblike blood vessels that connect arteries to veins and permit transfer of materials between blood and tissues

• plasma - the cell-free fluid part of blood and lymph

• extracellular fluid - fluid residing outside the cells that transport materials to and from the cells

• intracellular fluid - fluid residing inside the cells that provides the medium for cellular reactions

• lungs - the body’s organ of gas exchange

  • blood circulating through the lungs releases its carbon dioxide and picks up fresh oxygen to carry to the tissues

• intestine - the body’s long, tubular organ of digestion

  • the site of nutrient absorption

• liver - a large, lobed organ that lies just under the ribs

  • filters the blood, removes and processes nutrients, manufactures materials for export to other parts of the body, destroys toxins or stores then to keep them out of the circulation, and excretes fat-soluble waste products into the small intestine

• kidneys - a pair of organ that filter wastes from the blood, make urine, and release to the bladder for excretion from the body

→ blood and lymph deliver nutrients to all the body’s cells and carry waste materials away from them

→ blood also delivers oxygen to cells

→ the cardiovascular system ensures that these fluids circulate properly among all organs

The Hormonal and Nervous System:

• hormones - chemicals that are secreted and released by glands directly into the blood in response to conditions in the body that require regulation

  • these chemicals serve as messengers, acting on other organs to maintain constant conditions

• pancreas - an organ with two main functions

  1. making of hormones such as insulin

     • releases directly into the blood

       → exo = out

  2. exocrine function

     • making of digestive enzymes

       • releases through a duct in the small intestine

       → endo = in

• insulin - hormone from the pancreas that helps glucose enter cells from the blood

• glucagon - hormone from the pancreas that stimulates the liver to release glucose into the bloodstream when blood glucose concentration dips

→ glands secrete hormones that act as messengers to help regulate body processes

Nervous System:

• cortex - the outermost layer of something

  • brain’s cortex is the part of the brain where conscious thought takes place

• hypothalamus - part of the brain that senses a variety of conditions in the blood

  • temperature, glucose content, salt content, and others

  • signals other parts of the brain or body to adjust those conditions when necessary

• fight or flight reaction - the body’s instinctive hormone and nerve mediated reaction to danger

  • also known as a stress response

• neurotransmitters - chemicals that are released at the end of a nerve cell when a nerve impulse arrives there

  • diffuse across the gap to the next cell and alter the membrane of that second cell to either inhibit or excite it

• epinephrine - the major hormone that elicits the stress response

• norepinephrine - a compound related to epinephrine that helps elicit the stress response

• metabolism - the sum of all physical and chemical changes taking place in living cells

  • includes all reactions by which the body obtains and spends the energy from food

→ the nervous system joins the hormonal system to regulate body processes through communication among all the organs

→ together, the hormones and nervous systems respond to the need for food, govern the act of eating, regulate digestion, and call for the stress response

The Immune System:

• microbes - bacteria, viruses, and other organisms invisible to the naked eye

  • some cause diseases

  • also called microorganisms

• antigen - a microbe or substance that is foreign to the body

• immune system - a system of tissues and organs that defend the body against antigens, foreign materials that have penetrated the skin or body linings

• lymphocytes - white blood cells that participate in the immune response

  • B-cells and T-cells

• phagocytes - white blood cells that can ingest and destroy antigens

  • phagocytosis - the process by which phagocytes engulf materials

• T-cells - lymphocytes that attack antigens

  • T stands for the thymus gland of the neck → where T-cells are stored and matured

• B-cells - lymphocytes that produce antibodies

  • B stands for bursa → an organ in the chicken where B-cells were first identified

• antibodies - proteins, made by cells of the immune system, that are expressly designed to combine with and inactivate specific antigens

• ghrelin - a hormone secreted by the stomach that is thought to be a “hunger hormone”

→ the immune system enables the body to resist disease

→ inflammation is the normal, healthy response of the immune system to cell injury

→ chronic inflammation is associated with disease development and being overweight

The Digestive System:

• digestive system - the body system composed of organs that break down complex particles into smaller, absorbable products

  • the whole system, including the pancreas, liver, and gall baldder is sometimes called the gastrointestinal or GI system

• digest - to break down molecules into smaller molecules

  • a main function of the digestive tract with respect to food

• absorb - to take in, as nutrients are taken into the intestinal cells after digestion

  • the main function of the digestive tract with respect to nutrients

→ the digestive tract is a flexible, muscular tube that digests food and absorbs its nutrients and some non nutrients

→ ancillary digestive organs aid digestion

• peristalsis - the wavelike muscular squeezing of the esophagus, stomach, and small intestine that pushes their contents along

• segmentation - alternating forward and backward movement allowing for greater contact between the partially digested food and intestinal juices and enzymes

  • resulting in virtually complete digestion of the food we eat

• stomach - a muscular, elastic, pouchlike organ of the digestive tract that grinds and churns swallowed food and mixes it with acid and enzymes, forming chyme

• sphincter - a circular muscle surrounding and able to close a body opening

• chyme - the fluid resulting from the actions of the stomach upon food

• pyloric - valve the circular muscle of the lower stomach that regulates the flow of partly digested food into the small intestine

  • also called the pyloric sphincter

• small intestine - the seven metre length of small diameter intestine that is the major site of digestion of food and absorption of nutrients

  • below the stomach and above the large intestine

• large intestine - the portion of the intestine that completes the absorption process

• colon - the large intestine

• feces - waste material remaining after the digestion and absorption are complete

  • eventually discharged from the body

→ the digestive tract moves food through its various processing chambers by mechanical means

→ the mechanical actions include chewing, mixing by the stomach, adding fluid, and moving the tract’s contents by peristalsis

→ after digestion and absorption, wastes are excreted

• gastric juices - the digestive secretion of the stomach

• pH - a measure of acidity on a point scale

  • pH of 1 = strong acid

  • pH of 7 = neutral

  • pH of 14 = strong base

• mucus - a slippery coating of the digestive tract lining that protects the cells from exposure to digestive juices

  • the digestive tract lining is a mucus membrane

• bile - a cholesterol-containing digestive fluid made by the liver, stored in the gallbladder, and released into the small intestine when needed

  • emulsifies fats and oils into water, combining them

• pancreatic juice - fluid secreted by the pancreas that contains both sodium and bicarbonate (a neutralizing agent) and enzymes to digest carbohydrate, fat, and protein

• emulsifier - a compound with both water-soluble and fat-soluble portions that can attract fats and oils into water, combining them

• bicarbonate - a common alkaline chemical

  • a secretion of the pancreas

  • also active ingredient of baking soda

→ chemical digestion begins in the mouth (where food if mixed with an enzyme in saliva that acts on carbohydrates)

→ digestion continues in the stomach, where stomach enzymes and acid break down proteins

→ digestion then continues in the small intestine (the liver and the gallbladder contribute to bile that emulsifies fat, and the pancreas and small intestine donate enzymes that continue digestion so absorption can occur)

→ bacteria in the colon break down certain fibres

• microbiota - the mix of microbial species of a community

  • Ex. all of the bacteria present in the human digestive tract

  • microbiome - the collective genes of such a community

→ a substantial population of intestinal bacteria scavenge and break down fibres and other undigested compounds

→ the colon absorbs and uses products of bacterial metabolism; the bacteria and their products also interact with other organs and tissues

→ diet strongly influences the composition and metabolism of the intestinal bacteria

→ the healthy digestive system is capable of adjusting to almost any diet and can handle any combination of food with ease

Absorption and Nutrient Transportation:

• villi - fingerlike projections of the sheets of cells that line the intestinal tract

  • make the surface area much greater than it would otherwise be

• microvilli - tiny, hairlike projections on each cell of every villud that greatly expand the surface area available to trap nutrient particles and absorb them into the cells

→ the digestive system feeds the rest of the body and itself sensitive to malnutrition

→ the folds and villi of the small intestine enlarge its surface area to facilitate nutrient absorption through countless cells to the blood and lymph

→ these transport systems then deliver the nutrients to all the body’s cells

The Excretory System:

• irritable bow\el syndrome (IBS) - intermittent disturbance of bowel function, especially diarrhea or alternating diarrhea and constipation

  • associated with diet, lack of physical activity, or psychological stress

• nephrons - the working units in the kidneys

  • consisting of intermeshed blood vessels and tubules

• bladder - the sac that holds urine until time for elimination

→ the kidneys adjust the blood’s composition is response to the body’s needs, disposing of everyday wastes and helping remove toxins

→ nutrients, including water, and exercise help keep the kidneys healthy

Storage Systems:

• glycogen - a storage form of carbohydrate energy (glucose)

• adipose tissue - the body’s fat tissue

  • consisting of fat-storing cells and blood vessels to nourish them

→ the body’s energy stores are of two principle kinds

1. glycogen in muscle and liver cells

2. fat in fat cells

→ to achieve optimal function, the body’s systems require nutrients from outside

→ these have to be supplied through a human being’s conscious food choices

• carbohydrates - compounds composed of single or multiple sugars

  • the name means “carbon and water”

  • chemical shorthand is CHO → carbon, hydrogen, and oxygen

• complex carbohydrates - long chains of sugar units arranged to form starch or fibre

  • polysaccharides

• simple carbohydrates - sugars, including both single sugar units and linked paris of sugar units

  • the basic sugar unit is a molecule containing six carbon atoms, together with oxygen and hydrogen atoms

• added sugars - sugars and syrups added to a food for any purpose, such as to provide sweetness or bulk or to aid in browning (baked goods)

  • also called carbohydrate sweeteners

    • include glucose, fructose, corn syrup, concentrated fruit juice, and other sweet carbohydrates

• free sugars - all those “added sugars” added to food by manufacturers and consumers, plus those that occur naturally in fruit juices

• photosynthesis - the process by which green plants make carbohydrates from carbon dioxide and water using the green pigment chlorophyll to capture the sun’s energy

• chlorophyll - the green pigment of plants that captures energy from sunlight for use in photosynthesis

• sugars - simple carbohydrates, that is, molecules of either single sugar units or pairs of those sugar units bonded together

  • by common usage, sugar most often refers to sucrose

• glucose - a single sugar used in both animal and plant tissues for energy, sometimes known as blood sugar or dextrose

→ through photosynthesis, plants combine carbon dioxide, water, and the sun’s energy to form glucose

→ carbohydrates made of carbon, hydrogen, and oxygen, held together by energy-containing bonds

Sugars:

• monosaccharides - single unit sugar units

• disaccharides - paris of single sugars linked together

• fructose - a monosaccharide

  • sometimes known as fruit sugar

• galactose - a monosaccharide

  • part of the disaccharide lactose (milk sugar)

• lactose - a disaccharide composed of glucose and galactose

  • sometimes known as milk sugar

• maltose - a disaccharide composed of two glucose units

  • sometimes known as malt sugar

• sucrose - a disaccharide composed of glucose and fructose

  • sometimes known as table, beet, or cane sugar, or simply sugar

→ glucose is the most important monosaccharide in the human body

→ most other monosaccharides become glucose in the body

Starch:

• polysaccharides - another term for complex carbohydrates

  • compounds composed of long strands of glucose units linked together

    • also called complex carbohydrates

• starch - a plant polysaccharide composed of glucose

  • after cooking, starch is highly digestible by human beings

    • raw starch often resists digestion

• granules - small grains

  • starch granules are packages of start molecules

  • various plant species make starch granules of varying shapes

Glycogen:

• glycogen - a highly branched polysaccharides composed of glucose that is made and stored by liver and muscle tissues of human beings and animals as a storage form of glucose

  • glycogen is not a significant food source of carbohydrate and is not counted as one of the complex carbohydrates in foods

Fibres:

• fibres - the indigestibles parts of plant foods, largely non starch polysaccharides that are not digested by human digestive enzymes

  • although some digested by resident bacteria of the colon

  • fibres including cellulose, hemicelluloses, pectins, gums, mucilages, and the nonpolycaccharides lignin

• soluble fibres - food components that readily dissolve in water and often impart gummy or gel-like characteristics to foods

  • Ex. pectin from fruits

    • used to thicken jellies and jams

  • indigestible by human enzymes but may be broken down to absorbable products by bacteria in the digestive tract

• viscous - having a sticky, gummy, or gel-like consistency that flows relatively slowly

• insoluble fibres - the tough, fibrous, structures of fruits vegetables, and grain

  • indigestible food components that do not dissolve in water

→ human digestive enzymes cannot break the bonds in fibre, so most of it passes through the digestive tract unchanged

→ some fibre is susceptible to fermentation by bacteria in the colon

→ the body tissues use carbohydrates for energy

→ the brain and nerve tissues prefer carbohydrate as fuel

→ foods rich in soluble viscous fibres help control blood cholesterol

Digestive Tract Health:

• hemorrhoids - swollen, hardened (varicose) veins, in the rectum

  • usually caused by the pressure resulting from constipation

• appendicitis - inflammation and/or infection of the appendix, as sac protruding from the intestine

• diverticula - sacs or pouches that balloon out of the intestinal wall

  • caused by the weakening of the muscle layers that encase the intestine

  • the painful inflammation of one or more of these diverticula is known as diverticulitis

• butyrate - a small fat fragment produced by the fermenting action of bacteria on viscous, soluble

  • major energy source for the colon

Chapter 4: The Carbohydrates

• DRI committee recommends that 45%-65% of daily calories come from carbohydrates

• fats are no normally used as fuel by the brain & central nervous system

  • glucose is the primary energy source for nerve cells

• CHOs are a source of energy

  • carbohydrates → 4 cal/g

  • fat (lipid) → 9 cal/g

  • protein → 4cal/g

• carbohydrates contain energy that plants captured through photosynthesis

  • makes use of chlorophyll to capture energy from sunlight

• glucose produced by photosynthesis provides energy for the work of all parts of the plant

  • plants do not use all the energy stored in their sugars

    • some remains available for use by the animal or human that consumes the plants

      → carbohydrates are the first link in the food chain that supports all life on Earth

• carbohydrate-rich foods come almost exclusively form plants

  • milk is the only-animal-derived food that contains significant amounts of carbohydrate

Introduction:

carbohydrates meet your body’s energy needs :

• feeds your brain & nervous system

• keep your digestive system fit

• within calorie limit, help keep your body lean

• together with fats & protein , digestible carbohydrates add bulk to foods

• indigestible carbohydrates yield little or no energy but provide other benefits

• glycemic effect - emic = blood

  • extent food increases blood sugar

  • want slow steady absorption, no spikes/plunges

  • low GI (glycemic index) foods are best

    • regulate insulin levels

    • decrease lipid levels in blood

    • decrease obesity

• glycemic response

  • glycemic index - a measure of the ability of a food to elevate blood glucose and insulin levels

    • scores are compared with a standard, usually a white bread or glucose

    • a food’s score depends on several factors

    • effect of the multiple foods may have result in a different glycemic index than if that person had eaten the whitebread

• complex carbohydrates

  • starch & fibre

• simple carbohydrates

  • sugars

Fructose:

→ fruit sugar from corn and artificial sweeteners

• accounts for over 40% of sweeteners in our diet

• contributes an avg 132 cal/day/person

• handled differently by the body than glucose

• effect on other hormone signals that regulate food intake and body weight

• fructose metabolism in the liver favours fat synthesis

• not fruit

• does not stimulate insulin production

Sugars:

• the three single sugars (monosaccharides) are glucose, fructose, and galactose

  • fructose is the sweet sugar of fruit

  • galactose is a component of milk sugar

  • glucose, fructose, and galactose all have the same number and kind of atoms arranged in different ways

• the three double sugars (disaccharides) are lactose, maltose, and sucrose

  • lactose is milk sugar

    • it is made of glucose linked to galactose

  • maltose has two glucose units

    • it appears wherever starch is being broken down

  • sucrose is table sugar, which is obtained (FINISH)

• polysaccharides

  • starch (plant)

    • long chains of glucose molecules that can have very complex “branches” (digestible)

  • glycogen (animal)

    • long chains of glucose also — but branching pattern is different (digestible)

  • fibre (plant)

    • the special chemical bonds between the glucose (not digestible)

• insoluble fibres do not dissolve in water

  • less easily digested

  • the outer layers of whole grains, the strings of celery etc, contain insoluble fibres such as cellulose and hemicellulose

  • these fibres retain their structure and texture even after hours of cooking

  • they aid in the digestive system and ease elimination

• soluble fibres dissolve in water

  • forms gels (are viscous)

  • easily digested by bacteria in the human colon

  • found in barely, legumes, fruits, oats, vegetables

  • are associated with a lower risk of chronic disease

  • add a pleasing consistency to foods

    • thickening them

Why do nutrition experts recommend fibre-rich foods?

• fibre-rich foods supply vitamins, minerals, and photo chemicals

  • these foods also contain little to no fact

• viscous fibres such as those found in apples have significant cholesterol

Fibre and Cardiovascular Disease:

• lowering body cholesterol

  • food rich in viscous fibres lower blood cholesterol by binding with cholesterol-containing bile and carrying it out with the feces

    • bile is needed for digestion, so the liver responds to its loss by drawing on the body’s cholesterol to make more

• blood glucose control

  • viscous fibres trap nutrients & delay their transit through the digestive tract

    • as a result, glucose absorption slows & this helps maintain steady levels of blood glucose & insulin

      → large fluctuations in blood glucose & insulin are thought to be associated with the onset of the most common form of diabetes

Fibre and the Digestive Tract:

• fibre along with fluid intake, play a role

Healthy Weight Management:

• food rich in complex carbohydrates tend to be low in fats and added sugars

  • they therefore promote weight loss by providing less energy

  • fibres also creates feelings of fullness and delay hunger because they swell as they absorb water

• recommendations and intakes

  • for fibre

    • men, age 19-50: 38g/day

    • men, age 51+: 30 g/day

    • women, age 19-50: 25g/day

    • women, age 51+: 21 g/day

    • average person → 30g/day - hard to get, 2x higher than what the average person intakes

• good way to add fibre while lowering fat is to substitute out animal sources of proteins for plant sources of proteins

  • focus on eating 5-9 serving of fruits and vegetables each day

  • eat a variety of high-fibre foods and drink ample fluids

The Need for Carbohydrates:

• DRI committee recommends that 45%-65% of daily calories come from carbohydrate

• fats are not normally used as fuel by the brain and central nervous system

  • glucose is the primary energy source for nerve cells

• digestion and absorption of carbohydrates

  • to obtain glucose from the food the digestive system must first break down carbohydrates in the food into monosaccharides that can be absorbed

The Body’s Use of Glucose:

• glucose is the basic carbohydrate unit tat each cell uses for energy

  • the body maintains an internal supply for use in case of need

  • the body tightly controls its blood glucose concentration

  • carbohydrates also serve structural roles in the body

    • such as forming part of the mucus that protects body linings and organs

• inside a cell, glucose is broken in half, releasing some energy

  • these halves can be broken into smaller fragments

    • in which case, they cannot be reassembled into glucose

    • the small fragments can yield more energy as they are broken down to carbon dioxide and water

    • they can be formed into building blocks of protein or units of body fat

• below the healthy minimum

  • body fat cannot be converted into glucose to adequately feed the brain

  • with severe carbohydrate deficit the body must use protein to make glucose

    • diverting protein from critical functions of its own

    • therefore, carbohydrates prevent the use of protein for energy

      → this is the protein-sparing action of carbohydrate

  • the minimum DRI to feed the brain (carbs) and reduce ketosis is 130 grams a day for an average person

    • 3x or 4x this minimum amount is recommended

  • fat fragments usually combine with a compound derived from glucose before being used for energy

    • without this compound, fat fragments combine with each other producing acidic ketone bodies

      → the accumulation of ketone bodies in the blood (ketosis) can disturb normal acid-base balance

• ketosis

  • during pregnancy can cause brain damage to fetus

  • adults with chronic ketosis may face vitamin and mineral deficiencies, loss of bone minerals, altered blood lipids, increased kidney stone risk, impaired mood and sense of well-being, and glycogen stores that are too low to meet a metabolic emergency or support maximal high-intensity muscular work

  • the minimum DRI to feed the brain and reduce ketosis is 130 grams a day for the average person

Handling Excess Glucose:

• excess glucose is stored as glycogen

  • until the muscle and liver are full to capacity

• the conversation of excess glucose to fat requires many steps and costs a great deal of energy

  • when presented with both glucose and fat, the body prefers to store the fat and use the glucose to meet immediate energy needs

    • the maximizes energy storage

Think Fitness:

• a working body needs carbohydrate to replenish glycogen

  • when glycogen runs low, physical activity can seem more difficult

  • two hours before a workout eat a small snack of approx 300 calories in rich complex carbohydrates and drink some extra fluid

Glycemic Load:

• glycemic index multiplied by grams carbohydrates

• the glycemic index, along with glycemic load, may be important to people with diabetes who must regulate their blood glucose

• the glycemic load may be a better tool for diet planning than the glycemic index

  • the glycemic load of carrots is much lower than its glycemic index

Where To Find Carbohydrates in Diet:

• grains

  • nutrition authorities encourage people to consume this group in abundance

• vegetables

  • some are major contributors of dietary starch

    • sweet potato → 15 grams

    • carrot → 5 grams

• fruits

  • approx 15 grams

• meat/poultry/eggs/fish/nuts

  • no carbohydrates (other than nuts)

• legumes

  • 15 grams

  • BEST SOURCE

• milk/cheese/yogurt

  • 12 grams

  • contribute protein as well as important vitamins and minerals

  • milk products vary in fat content

Dairy Products:

• 75%-95% of people lose much of their ability to produce lactase (enzyme)

  • this results in lactose intolerance, symptoms of which include nausea, pain, diarrhea, excessive gas

  • intestinal bacteria ferment the undigested lactose resulting in the production of gas and intestinal irritants

• the inability to digest lactose affects people to differing degrees

  • people often overestimate the severity of their lactose intolerance

    • a mistake that could adversely affect the health of their bones

• drinking milk with other foods may increase lactose intolerance

• sometimes sensitivity to milk is not due to lactose intolerance but to an allergic reaction to the protein in the milk

  • individuals with milk allergy often cannot tolerate cheese or yogurt

    • finding nondairy calcium sources

• added sugars - sugars added to food for any purpose such as to add sweetness, bulk, aid in browning of baked good

• naturally occuring sugars - sugars that are not added to food but are present as its original constituents

Chapter 5: Lipids

• regulations on trans fats

  • 2% of total fat (oil and margarine)

  • 5% in all other foods

Chemistry:

• phospholipid (phosphatidylcholine)

• triglyceride (triacylglycerol) - used as an energy molecule

  • glycerol + 3 fatty acid chains

  • variations

    • length of fatty acid

• steroid (cholesterol) - neutral, just a molecule (not good or bad)

Slide Image:

→ white ball = carbon - stored energy

→ pink ball = organize

Introducing Lipids:

• lipids in foods and in the human body fall into three classes

  1. triglycerides

     • 95% of all lipids in foods and the human body

  2. phospholipids

     • ex. lecithin

  3. sterols

     • ex. cholesterol

• energy storage (Table 5-1)

  • fat - more efficient energy storage takes less space

    • 9 cal/g

  • glycogen - less efficient more space

    • 4 cal/g (more H2O)

• glucose, in the form of glycogen, is not the body’s major form of energy

  • glycogen stores a large amount of water

• FINSIH
  

• most body cells can store only limited fat storage

  • these fat cells seem to expand indefinitely

    • the more fat they store, the larger they grow

  • adipose (fat) tissue secretes hormones and produces enzymes that influence food intake and affect the body’s use of nutrients

• body fat

  • the amount of a normal-weight person is more than sufficient to provide energy to battle a disease should the person become ill and stop eating for while

• essential nutrients

  • the fat-soluble vitamins (A, D, E, and K) are soluble in fat

    • found mainly in foods that contain fat

      → absorbed more efficiently from these foods

      → fat aids in the absorptions of some phytochemicals

• essential fatty acids

  • serve as raw materials from which the body makes certain required molecules

    • omegas

Usefulness of Fats in Food:

• the energy density of fats makes foods rich in fat vulnerable in many situations

  • ex. hunter or hiker need to consume a large amount of food → energy travel long distances or to survive in intensely cold weather

    • for a person who is not expending much energy in physical work, the same high-fat foods may deliver many unneeded calories in only a few bites

• fat contributes to satiety

  • the feeling of fullness or satisfaction that people experience after meals

  • the fat of swallowed food triggers a series of physiological events that slow the emptying that slow

• saturated

  • bunch of carbons and hydrogens attached to each other with single bonds

• monounsaturated

  • double bonds

• polyunsaturated

  • more than one double bond

Animals:

• unsaturated fats

  • go into the lymph

Saturated vs Unsaturated Fatty Acids:

• saturated fatty acids - every available bonds from the carbons is holding a hydrogen

  • exceptions

    • tropical plant oils

      → coconut oil - baked goods, non-dairy creamers, granola

      → palm oil - cheaper, beware “may contain”

      → vegetable oil - could be any oil

• monounsaturated fatty acid (MUFA) - contains one points of unsatruation

• polyunsaturated fatty acids (PUFA) - contains two or more points of unsaturation

• points of saturation

  • vulnerable to attack by oxygen

  • when oxidized the oils become rancid

    • cooking oils should be stored in tightly covered containers that exclude air

    • if stored for long periods, they need refrigeration to retard oxidation

• degree of saturation - affects the temperature at which the fat melts

  • in general, the more unsaturated the fatty acids, the more liquid the fat is at room temperature

  • in general, the more unsaturated the fatty acids, the firmer the fat is at room temperature

• trans fats - contain unusual fatty acids that are formed during processing

  • would have to do in a lab

  • formed by hydrogenation of poly saturated fatty acids

  • trans fatty acids

    • unusual unsaturated fatty acids

    • similar in shape to saturated fatty acids

    • not made by the body

    • naturally occur in tiny amounts mainly in dairy foods and beef

    • affect the body’s health

  • consumption of trans fats

    • raise LDL and lower HDL cholesterol

    • produce inflammation → increasing the risk of heart disease

    • DRI: as little as possible

  • trans fats and margarine

    • the stick varieties, especially, contain almost 50% of their fat as trans fat

    • many other foods contribute a greater percentage of trans fat to the diet

• hydrogenated veg oils - chemically converted from unsaturated to saturated by addition of hydrogen

  • easy to handle

  • easy to spread

  • store well

• hydrogenation - the process of adding hydronic to unsaturated fatty acids to make the fat more solid and resistant to chemical changes of oxidation

Other Lipids:

1. phospholipids

   • soluble in H20

   • emulsifiers - substance that mixes with both fat and water and personality disperses the fat in the water (forming an emulsion)

     • in salad dressing, vinegar and oil separate to form two layers, whereas mayonnaise (also made of vinegar and oil), never forms two separate layers → the difference is the presence of lecithin (an emulsifier in mayonnaise)

2. sterols

   • large, complicated molecules consisting of interconnected rings of carbon atoms with side chains of carbon, hydrogen, and oxygen

   • the sterol cholesterol serves as the precursor for making bile

     • an emulsifier made in the liver and stored in the gallbladder

       → emulsifies fats in such a way that enzymes in the watery fluids may contact it and split the fatty acids from their glycerol for absorption

   • vitamins D and sex hormones are also sterols

No Gallbladder:

• gallbladder is just a storage organ

• liver still procures bile

  • delivers it continuously to the small intestine

• those who have had their gallbladder removed must initially reduce their fat intakes

  • they can no longer store bile and release it at mealtime

  • so they can handle only a little fat at a time

Digestion of Fats:

• in the mouth (minimal)

  • lingual Li passes from salivary glands

• in stomach (minimal)

  • gastric lipases from stomach

• in small intestine

  • bile

  • pancreatic lipases (from pancreas)

  • hepatic lipases (from liver)

  • triglycerides → fatty acids + glycerol

Transport Fats:

• larger products of lipid digestion

  • without a Eucharist to keep it dispersed, large lipid globules would separate out of the water you blood and disrupt the bloo’’s normal function

• lipoproteins - clustered of lilies associated with protein

  • serve as transport vehicles for lipids in blood and lymph

• low-density lipoproteins (LDL) - transport cholesterol and other lipids to body tissues

• high-density lipoproteins (HDL) - carry cholesterol from body cells tot he liver for disposal