Nutrition Notes

MODULE 1: NUTRITION AND NUTRIENTS

Lecture 1: Nutrients and Food Choices

Chapters Covered: 1 and 2

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What is Nutrition?

• Nutrition: The study of how compounds in foods nourish and influence body functions and health.

• Nutrients: Components found in food including:

  • Water

  • Carbohydrates

  • Proteins

  • Fats

  • Vitamins

  • Minerals

• Nutrition examines how these nutrients interact with the body and how to create a nutritious diet.

• Important Fact: By age 65, an individual has consumed more than 70,000 meals.

Importance of Good Nutrition

• Role of Nutrients:

  • Build the body (skin, muscle, and blood).

  • Support growth, maintenance, and repair of body tissues.

• Consequences of Nutritional Imbalance:

  • Deficiencies, excesses, and imbalances can lead to malnutrition and various diseases.

• Impact on Health:

  • Proper nutrition significantly influences health and can mitigate risks for diseases, including cancer.

  • Good nutrition can reduce the risk of diseases

You Are What You Eat

• Key Nutrients:

  • Vitamins

  • Minerals

  • Fats

  • Proteins

  • Carbohydrates

  • Water

• Concept of Eating: Reflects dietary choices

Nutrition and Health

• Personal lifestyle choices and genetics can significantly affect health outcomes.

• Certain causes of death are related to nutrition:

  • Heart diseases

  • Cancers

  • Strokes

  • Diabetes mellitus

What are the Nutrients?

• Nutrient- chemical that an organism needs to live and grow or a substance used in an organism

  • Come from food and provide:

    • Energy (measured in kilocalories or kcal)

    • Building blocks for the body

    • Maintenance for cell functions (help with enzymatic reactions)

Enzymes: Definition and Function

• Enzyme: A molecule that accelerates or catalyzes chemical reactions.

  • Involved in breaking down the foods we eat so the body can use them

  • Names of enzymes usually end in the suffix -ase

• Substrate: The molecule acted upon by an enzyme; binds at the active site.

The Six Classes of Nutrients

• Categories:

  • Carbohydrates (also known as carbs, saccharides, or sugars)

    • Contain carbon, oxygen, and hydrogen

  • Fats (known as lipids or fatty acids)

    • Contain carbon, oxygen, and hydrogen

  • Proteins

    • Contains carbon, oxygen, hydrogen, and nitrogen

  • Vitamins

    • Contain carbon, oxygen, and hydrogen

  • Minerals

  • Water

Elements in Nutrients

• Organic Compounds- nutrients containing carbon

  • Specific Nutrient Composition:

  • Proteins are the only nutrient containing nitrogen

  • Vitamins

  • Fats

  • Carbohydrates

• Minerals are inorganic

• Carbon Content: Carbon, oxygen, hydrogen, and nitrogen are essential elements in organic nutrients.

Nutrients and Their Functions

• Macronutrients- Essential nutrients needed in larger amounts which yield energy:

  • Carbohydrates: 4 kcal/g

  • Fats (Lipids): 9 kcal/g

  • Proteins: 4 kcal/g

  • Note: Alcohol provides energy (7 kcal/g) but is not classified as a nutrient because it is not necessary for survival (it is not needed to live and grow)

• Micronutrients- non energy-yielding nutrients

  • Vitamins:

    • Organic compounds required in small quantities for bodily functions.

    • Assist in body processes but are vulnerable to destruction and must come from dietary sources.

  • Minerals:

    • Inorganic elements needed in varying amounts for structural functions.

    • Indestructible and often assist enzyme functions.

Water

• Vital for numerous body processes including:

  • Serving as a fluid medium inside and outside of cells.

  • Acting as a lubricant for joints, eyes, and gastrointestinal tract.

  • Providing a protective cushion for organs.

  • Involved in chemical reactions, like those in energy production.

  • Key role in nutrient and oxygen transport and waste removal.

• Daily Need: Large amounts of water are essential (exact amounts vary by individual).

What is a Calorie?

• Definition: A calorie is a unit of measurement for energy

• Specifically, it is “the amount of heat it takes to raise the temperature of 1 gram of water by 1 degree Celsius.”

• Energy in food is typically measured in kilocalories (kcal) but often just referred to as calories

• To measure the amount of calories in a food you use a bomb calorimeter

  • 1 degree change in temperature in 1 gram of water represents 1 calorie of energy

Measuring Kcalorie Values of Macronutrients

• Carbohydrates: 4 kcal/g

• Fats (Lipids): 9 kcal/g

• Proteins: 4 kcal/g

• Alcohol: 7 kcal/g (not a nutrient because it doesn’t support growth)

Measuring Kcalorie Values of Micronutrients

• Vitamins: 0 kcal/g

• Minerals: 0 kcal/g

• Water: 0 kcal/g

Additional Nutritional Concepts

• Essential Nutrients: Nutrients the body cannot synthesize, found in all classes of nutrients

• Phytochemicals: Non-nutrient compounds from vegetables that give color, taste, and other characteristics (Ex: carotenoids, antioxidants)

  • Many phytochemicals are bioactive in food so they positively contribute to health

  • Ex: Carotenoids give carrots their orange color

• Bioactive Foods: non-essential molecules present in foods that can influence one or more metabolic processes

• Fibers: Indigestible parts of plants, aid health yet yield 0 kcal/g.

  • promote digestion and health GI tract

Nutrition Recommendations

• For the public:

  • Dietary Reference Intakes (DRIs) —> nutrient based focusing on macro and micro nutrients

  • MyPlate and other food guides —> food based with recommendations for food groups like fruits and vegetables

• For professionals:

  • DRIs

  • Dietary Guidelines for Americans

  • Healthy People 2020

• Approaches: Food-based and nutrient-based recommendations.

Dietary Reference Intakes (DRI)

• DRIs: Set intake standards for nutrients, including water, fibers, and caloric energy.

• Components include: green for micronutrients

  • Recommended Dietary Allowances (RDA)

  • Adequate Intakes (AI)

  • Estimated Average Requirements (EAR)

  • Tolerable Upper Intake Levels (UL)

Nutrient Consumption

• Not everyone in a population has the same nutrient needs —> this can be represented on a graph

  • The need for the whole population can also be visualized in the same graph based on the curve

  • The middle of the curve divides the population in half with 50% on either side and is the average requirement

    • This results in a bell curve because most people should be consuming the average

    • If the average amount is consumed, everyone to the left will be covered (around 50%)

    • If we move farther to the right of the curve and pick an amount being consumed, the need of almost everyone in the population will be met

  • Consuming an amount past the right boundary of the curve means consuming more than anyone in the population needs (consuming too much)

• Illustration: Different nutrient needs for individuals indicating that consumption amounts may vary widely for healthful dietary choices.

RDA and Adequate Intakes (AI) - recommended intake values

• RDA (Recommended Dietary Allowance): Meets the needs of almost all healthy people in a population (≈ 97%).

  • Generally 2 standard deviations above the EAR (estimated average requirements)

• AI (adequate intakes): Established when there is insufficient evidence to create an RDA; based on estimates of intakes that appear to maintain nutrition status

  • Based on observed or experimentally determined approximations of nutrient intake

  • Does not have a known position on the requirement curve

  • Less precise because it doesn’t have a known position on the requirement distribution

• Both vary with age, sex, height and physiological status like pregnancy

• Both focus on micronutrients (vitamins and minerals), waters and fibers, and dictate amount to ensure adequate intake and prevent deficiencies and chronic disease

EAR (Estimated Average Requirements)

• EAR- intake value that meets the needs of 50% of the healthy individuals in a population

  • Used as the recommendation for caloric intake to prevent overeating

  • Population-wide average

  • Females need around 2000 Kcal/day

  • Males need around 3000 Kcal/day

Nutritional Intake Recommendations by Age and Gender

• Detailed recommendations for Thiamin intake, RDA levels vary by age and physiological states (e.g., pregnancy).

Understanding the DRIs

• Key Points:

  • RDA or AI covers the needs of 97% of specific populations.

  • EAR is targeted for 50%, applied for caloric needs and avoiding over-nutrition.

  • Average caloric needs:

  • Females ~ 2000 kcal/day

  • Males ~ 3000 kcal/day

Tolerable Upper Intake Levels (UL)

• Definition: Maximum of usual daily nutrient intake likely to pose no risk of harmful health effects, not intended as goal intake but as a safety ceiling.

• Assessment Tool: Guide for supplements and fortified foods to avoid toxicity from excess intake.

• Not enough info to set Upper Intake Level for all nutrients

Example UL for Nutrients

• Vitamin D:

  • UL for adults set at 50 µg/day, which equates to 2000 IU.

  • Having more than that can negatively impact your health

Application of DRIs in Dietary Assessment

• Framework for evaluating nutrient intake concerning vitamins, minerals, water, fibers, and caloric needs.

• For vitamins, minerals, water, and fibers (non-energy yielding)

  • Intake that falls between RDA and Upper Limit (UL) makes sure you are getting enough but not too much of that nutrient

  • Way too much or way too little of a nutrient puts you at a 100% risk for inadequacy or excess

  • Adequate intake falls between RDA and UL

    

Acceptable Macronutrient Distribution Ranges (AMDR)

• Macronutrients provide calories → carbs, fats, and proteins

• ADMR- distribution range of intakes recommended for macronutrients, associated with reduced risk of chronic disease

  • Expressed as percent of total calories that should come from each macronutrient

• Carbohydrates: 45-65% of total energy intake

  • Men (3000 Kcal total) → 50% of that would be 1500 kcal a day

    • Carbs have 4 kcal/g so 1500 kcal/4 would be 375g of carbs a day

• Proteins: 10-35% of total energy intake

• Fats: 20-35% of total energy intake

Daily Value (DV)

• Found on food packaging, these values reflect dietary needs for an average person consuming 2000 kcal/day.

  • One set of values that applies to everyone → about right for moderately active women, teen girls, and sedentary men

• Simplifies comparison among food products and helps tell whether or not a food has a lot or little of a nutrient

Example of Nutrition Facts and Labeling

• Sample label outlining nutritional content and percentages of daily value for key nutrients.

Summary and Review Points

• Key Themes Discussed:

  • Nutrition = study of nutrients in food and in the body

  • Nutrition affects long-term health (cancer, strokes, diabetes).

  • Nutrients provide energy, building blocks, and help maintain body functions

  • Nutrient classification:

    • Macronutrients (energy-yielding): Carbohydrates, Fats, Proteins.

    • Micronutrients (non energy-yielding): Vitamins, Minerals, Water.

Nutrient Classifications Recap

• Macronutrients: Energy-providing nutrients requiring higher intakes (Carbohydrates - 4 Kcal/g, Fats - 9 Kcal/g, Proteins - 4 Kcal/g).

• Micronutrients: Non-energy yielding essential nutrients, vitamins, and minerals.

• Water’s Role: Integral for processes, with additional components like

• Phytochemicals and fibers present in food, contributing to health

Dietary Reference Intakes (DRI) Overview

• DRIs provide nutrient intake benchmarks and adapt based on age, sex, and physiological status.

• Components include RDA (recommended dietary allowances), AI (adequate intake), EAR (estimated average requirements), and UL (upper intake levels) reflecting group-specific needs.

• RDA or AI covers the need of 97% of population (specific life stage and sex)

  • Micronutrients (non energy-yielding) → vitamins and minerals

  • Water and fibers

  • Amount t ensure adequate intake and prevent deficiencies and chronic illnesses

• EAR covers caloric need of 50% of a population

  • Prevent over nutrition

• UL is ceiling not a goal

  • highest level of intake that doesn’t pose a risk

Additional Recommendations: AMDR and DV

• AMDR for energy-yielding nutrients

  • ranges of recommended intakes associated with reduced risk of chronic disease

  • carbs = 45-65% of total calories

  • fat = 20-35% of total calories

  • protein = 10-35% of total calories

• Daily Value for average consumer needs on food labels

  • Set of values on food label that applies to everyone

  • based on the “average” person consuming 2000 kcal/day

Sample Questions for Revision

• Can nutrition affect certain cancers?

  • Yes, maintaining proper nutrition can reduce the risk of chronic illnesses including cancer

• What functions do nutrients serve?

  • Nutrients support growth, maintenance, and repair of body tissues as well as build the body (skin, blood, muscle)

• What are the six classes of nutrients?

  • Carbohydrates

  • Fats

  • Proteins

  • Vitamins

  • Minerals

  • Water

• Which nutrients are organic and what are their caloric values?

  • Organic nutrients are those containing carbon

    • Carbs: 4 kcal/g

    • Fats: 9 kcal/g

    • Proteins: 4 kcal/g

    • Vitamins: 0 kcal/g

• What is the purpose of the Dietary Reference Intakes?

  • Set intake standards for nutrients, fibers, and energy

• How are vitamins recommended intakes determined?

  • Vitamins are micronutrients (non energy-yielding) so their recommended intakes are determined using RDAs, AIs (in the event there isn’t enough evidence to create an RDA), and ULs

Lecture 2: Decoding the Food Label

Food Label Regulations

• Tightly controlled by the Food and Drug Administration (FDA) to allow consumers o make choices that support their health and wellbeing

• Only apply to foods → NOT dietary supplements

  • Foods are tightly controlled and monitored but supplements are not

• Code of Federal Regulations, Title 21 has laws and regulations pertaining to food

  • Industry not following the rule causes government agencies to get involved and can have serious legal consequences along with recalls

• All small packaged foods are required to label EXCEPT

  • Very small companies

  • Plain coffee, tea, and spices

  • Items prepared and sold in the same establishment

  • Fresh fruits and vegetables

  • Some fresh meats

What’s on the Food Label

• Food labels are regulated by the FDA and must contain the following

  • Product name

  • Company name and address

  • Ingredients by descending order of weight (listed in order of decreasing amounts)

    • Ex: In a bottle of ketchup tomatoes are listed first and the second one by weight is sugar

  • Amount in the product

  • Product bar code

  • Nutrition facts panel

• To avoid having sugar listed as the first ingredients, a lot of labels will list different types of sugar

• You can also find descriptive terms about the product (also tightly regulated)

  • Nutrient content claim- characterizes the level of nutrient in the food (ex: “fat free” or “less sodium”)

    • <5% DV = low source

    • 10-19% DV = good source

    • ≥20% DV = high source

  • Health claim- claim that links food components with disease states

    • Must meet FDA criteria

    • Nutrient or food substance must be related to disease or health conditions for which most people, or a specific group, are at risk

    • Ex: calcium and reduced risk of osteoporosis

    • Ex: a diet low in total fat may reduce the risk of some cancers

  • Structure-function claims- describe the effect that a substance has on a structure/function of the body

    • Do not make references to diseases

    • Requires FDA notification but not approval → no need to submit evidence

    • Ex: “supports immunity and digestive health” or “calcium builds strong bones”

    • Can look a lot like a health claim

      • Health claim = lowers cholesterol

      • Structure-function claim = helps maintain normal cholesterol level

      • A small label should say that the FDA has not evaluated the claim

• Allergen Statement- labels must list in plain English the tope 8 allergens in the US

  • They can be listed in the ingredients OR they can added in a warning at the end

Nutrition Facts Panel

• Food label MUST contain the nutrition facts panel (based on 2000 calories/day intake)

• Nutrition facts panel must contain the following

  • Serving size → FDA established specific serving sizes that reflect amounts people customarily consume

    • Beverages = 8 oz

    • Ice cream = ½ cup

  • Total food energy (Kcals or calories)

  • Food energy from fat (Kcals from fat)

    • Total fat (g)

    • Saturated fat (g)

    • Trans fat (g)

    • Cholesterol (mg)

  • Sodium (mg)

  • Total carbohydrates (g)

    • Dietary fibers (g)

    • Sugars (g)

      • Added sugars

  • Protein (g)

  • Vitamin A, Vitamin C, Iron, Calcium (% Daliy Value)

• FDA New Nutrition Facts Panel

  • Changes were made like making serving sizes that better reflect portion sizes and making the calories per serving larger and in bold

Short Cut Labels

• Most of the info on the product and food label can be put in short-cut labels

  

Example Questions

What types of fats have to be listed on a food label?

• Total fat, saturated fat, and trans fat as grams with saturated fat and trans fat being listed under total fat

How are ingredients listed on a food label?

• In order of decreasing weights → first ingredient is present in the highest weight and they go down from there

What vitamins and minerals have to be listed on a food label?

• Vitamin A, Vitamin C, Iron, and Calcium

Give an example of a health claim.

• Diets low in saturated fat and cholesterol may reduce the risk of heart disease

Give an example of a structure/function claim.

• Calcium builds strong bones

Lecture 3: Dietary Guidelines for Americans

Refresher

• Food is composed of nutrients that furnish energy, building blocks, and help maintaining body functions

• 6 classes of nutrients:

  • carbohydrates

  • fat

  • proteins

  • vitamins

  • minerals

  • water

• The DRI (Dietary Reference Intake) = RDA/AI, EAR, UL

  • Vitamins and minerals = RDA, AI

  • Energy = EAR

Where do you find the different nutrients?

• Carbohydrates (also call saccharides)

  • One (mono-) or two (di-) saccharides are small molecules that are easily absorbable

    • These are sugars

    • Ex: candies, pastries, honey, jam, fruits

  • Polysaccharides (long chain) require digestion

    • These are grains

    • Grains can also contain fibers (whole grains)

    • Ex: starch, corn, bread, potatoes

• Vegetables

  • Contain mono- and polysaccharides, fibers, and phytochemicals

• Proteins

  • Found in meat, fish, eggs, soy, legumes (lentils, beans), and dairy (milk, cheese)

  • Legumes- plants in the family fabaceae (or leguminosae), or the fruit or seed of such a plant

    • Have symbiotic nitrogen-fixing bacteria in structures called root nodules

    • Ex: alfalfa, clover, peas, beans, lentils, lupins, mesquite, peanuts, soybeans

    • A legume fruit is a simple dry fruit that usually opens a long seam on 2 sides (common name for this type is a pod)

• Fats (Lipids)

  • There are different types of fats

    • Fatty acids (most common)

      • There are also different types of fatty acids

      • Essential fatty acids = omega 3 and omega 6

        • Omega 3 = fatty fishes, canola oil, walnut

        • Omega 6 = sunflower oil, margarine

      • Essential nutrients = nutrients the body cannot make itself, must come from food

      • Trans fat- unsaturated fat with a trans-isomer fatty acid(s), formed during processing in food production and are not health

    • Steroids

    • Phospholipids

• Micronutrients

  • Minerals and vitamins are found in different types of foods

  • Consuming a variety of foods ensures adequate intake

  • Ex: iron comes from red meat, calcium from dairy, vitamins from fruits/vegetables

    

• Phytochemicals are mostly found in fruits, vegetables, and whole grain foods

What is a healthy diet?

• Adequacy: a diet should provide enough of each essential nutrient

• Balance: balance the diet to provide enough of everything

• Calorie control: energy intake should not excess needs

• Moderation: certain foods should be limited for health’s sake

• Variety: diet should provide enough of each essential nutrient

• Consume a variety of foods balanced by a moderate intake of each food

• Food providing

  • Essential nutrients from all 6 classes

  • Fibers and phytochemicals → whole grains, fruits, and vegetables

• Whole foods are the basis of a nutritious diet (non-processed food)

  • Meat, fish, fruits, vegetables etc

Whole Foods

• Foods that are unprocessed and unrefined, or processed and refined as little as possible

• Whole foods typically do not contain added ingredients, such as salt, carbohydrates, or fat

• Ex: unpolished grains, beans, fruits, vegetables, and non-homogenized dairy products

• Food processing is the transformation of raw ingredients into food, or food into other forms

All foods are not created equal

• Nutrient density → comparison of vitamin and mineral content to number of kcals

• Empty calories → provides kcals and few to no other nutrients

  • increase the energy of the food and reduce the nutrient density

• Discretionary calories → difference between calories needed and those in food required to supply nutrients

• Energy density → comparison of the kcal content to the weight of the food

Food Groups

Fruits

• Any fruit or 100% fruit juice counts as part of the fruit group

• Fruits may be fresh, canned, frozen, or dried, and may be whole, cut-up, or pureed

Vegetables

• May be raw or cooked; fresh, frozen, canned, or dried/dehydrated

• May be whole, cut-up, or mashed

• Starchy vegetables have long chain polysaccharides, are energy dense, and some countries classify them as grains

  Dark Green	Red & Orange	Starchy	Other
  Broccoli  Collard greens  Spinach  Romaine	Butternut squash Carrots  Tomatoes	Corn  Black-eyed peas Potatoes  Lima beans	Artichoke Avocado Cauliflower Green beans Okra

Grains

• Any food made from wheat, rice, oats, cornmeal, barley or another cereal grain is a grain product

• Ex: bread, pasta, oatmeal, breakfast, cereals, tortillas, grits

• Whole grains: contain the entire grain kernel (bran, germ and endosperm → fibers)

• Refined grains: milling removes dietary fiber, iron, and many B vitamins

• Try and make at least half of your grains whole grains

  Whole Grains	Refined Grains
  cracked wheat  oatmeal  whole cornmeal  brown rice	white flour  de-germed cornmeal  white bread  white rice

Protein

• Includes meat, poultry, seafood, beans and peas, eggs, processed soy products, nuts, and seeds

Dairy

• Cream cheese, cream, and butter, have little or no calcium - they are not included

• Calcium-fortified soymilk is also part of the dairy group

Average American diet

• Too much grains and proteins

• Too much meats and beans

• Not enough fruits and vegetables

• Not enough milk

• Unhealthy diets and lack of exercise are linked with increasing obesity rates in the US

• Increasing prevalence of obesity among US adults by state

Average American diet is high in

• Sodium (salt from processed foods)

• Saturated fat

• Calories

Average American diet is low in

• Vitamin D

• Calcium

• Fiber

Dietary Guidelines for Americans (DGA)

• Target audience: health educators, health professionals, policymakers

• Offer food-based strategies for achieving DRI values

• Updated every 5 years to reflect advancing science by the US Department of Agriculture (USDA) and Health & Human Services (HHS)

• For healthy people ages 2+ years

  • Includes people at risk for chronic disease

Shortfall and Over-consumed Nutrients

Chronically undersupplied in US diets

• Vitamin A

• Vitamin D

• Folate

• Calcium

• Iron

• fiber

• Potassium

Chronically oversupplied in US diets

• Saturated fat

• Added sugars

• Sodium

Healthy People 2030

National goals to help the US identify pressing health threats and goals to reduce those threats

They are set every 10 years

MODULE 2: DIGESTION, ABSORPTION, TRANSPORT

Why do we want to eat?

• Food consumption can be trigger by a physiological and/or psychological drive to eat

• Hunger- physiological sensation that prompts us to eat

• Satiety- the feeling of being full

• Appetite- psychological desire to eat certain foods

Hormone- a chemical released by one or more cells that affects cells isn other parts of the organism

• Body’s chemical messengers that travel in the bloodstream to tissues or organs

• Only a small amount of a hormone is required to have an effect

• Hormones affect different processes including

  • Growth and development

  • Metabolism- how your body gets energy from the foods you eat

  • Sexual function

  • Reproduction

  • Mood

• Some hormones stimulate food intake/hunger

• Some hormones produce a feeling of satiety

• Hormones are released from the gut and other organs (fat tissue, pancreas) and act on the brain to promote hunger or satiety

• Food in the GI tract is outside the body → the GI tract is one continuous, hollow tube from the mouth to the anus that acts as a passage open to the external environment

• Taking food into the mouth does not assure admission to the body

• Food has to undergo digestion, absorption, and transport to be absorbed in the body

  • Take place in the GI tract

Gastrointestinal (GI) Tract

Organization

• Series of organs, from the mouth to the anus

• Accessory organs- not part of the GI tract, are also involved in digestive processes

  • Salivary glands, liver, pancreas, gallbladder

Functions

• Ingestion

• Transport, propulsion and mixing of Gi contents

• Secretion of digestive juices

• Digestion

• Absorption

• Elimination

Gastrointestinal (GI) tract- a series of organs arranged as a long tube that works together to process foods

• Digestion- process of breaking down food into individual molecules small enough to be absorbed through the intestinal wall to release nutrients

  • 2 types of digestions

    • Mechanical

    • Enzymatic (chemical)

• Absorption- the process of moving nutrients from the GI tract into the bloodstream

• Transport- the process of moving absorbed nutrients throughout the body through the circulatory and lymph systems

• Elimination- the excretion of undigested and unabsorbed food through the feces

Anatomy of GI Tract

1. Mouth → digestion begins in the mouth

2. Esophagus → “tube” from mouth to stomach

3. Stomach

4. Small intestine

5. Large intestine

The Mouth

Mechanic

• Teeth break down food, which is mixed with saliva

• Affects how long food will stay in the stomach

Enzymatic

• Salivary glands secrete enzymes

  • Salivary amylase → carbs digestion

  • Lipase → fats digestion

Saliva also helps with lubrication and contains haptocorrin

• Haptocorrin- protein secreted by the salivary glands that binds to the acid-sensitive vitamin B12 and protects it in the stomach

Swallowing process

Epiglottis closes over larynx, blocking the entrance to the lungs via the trachea so that food can pass into the esophagus

Esophagus - not under conscious control

Structure - 12'“ tube

• 2 sphincters: the upper esophagus sphincter (UES) and the lower esophagus sphincter (LES)

• Upper esophagus sphincter (UES) opening is triggered by swallowing

• Lower esophagus sphincter (LES) protects esophagus from stomach acids (one-way valve mechanism)

Function

• Transports food from mouth to stomach

• Muscle contraction (peristalsis) and gravity aid food movement

Digestion

• Mechanical (limited)

• Enzymatic- carbs digestion continues (salivary amylase)

Stomach

Structure → muscular sack that can expand

Digestion

• Mechanical (3 muscle layers) → stomach muscles grind food into paste called chyme

• Enzymatic

Chemical Digestion

• Protein digestion is starting in the stomach

• Carbs and fats digestion still ake place but its not as important due to the low pH

• Gastric acid has pH 1.5 to 3.5

Secretions → several substances are being secreted by the stomach

1. Pepsin - protein digestion (enzyme)

2. Gastrin - hormone that stimulates stomach to release secretions

3. Gastric (hydrochloric) acid - unravels proteins, kills bacteria, activates pepsin, helps absorption of iron, calcium

4. Mucus - secreted by goblet cells, protects stomach, moistens food, prevents autodigestion

5. Intrinsic factor - protein needed for vitamin B12 absorption

Physiology and secretions

• Goblet cells- secrete mucus

• Chief cells- secrete enzyme

• Parietal cells- secrete gastric acid

Functions

• Hydration, dilution of the chyme

• Homogenization of chyme

• Hydrolyze food

  • Enzymes from salivary glands

  • Gastric enzymes

  • Gastric acid (pH 3-5)

• Regulates digestion and absorption via gastric emptying

Gastric emptying

• Depends on

  • Quality of food in the stomach

  • Quality

• An increase in stomach content, caloric content, viscosity and fiber content will decrease gastric emptying

• Gastric emptying is also influence by sex, physical activity, pregnancy

  ↑ Fluidity	↑ Gastric emptying
  ↑ Viscosity	↓ Gastric emptying
  ↑ Stomach content	↓ Gastric emptying
  ↑ Fat / caloric contents	↓ Gastric emptying
  ↑ Fiber contents	↓ Gastric emptying

• Once in the small intestine, chyme inhibits motor activity of stomach

Review

• Food undergoes different processes:

  • Digestion  

  • Absorption 

  • Transport

  • Elimination 

• Gastrointestinal (GI) tract: 

  • Is a series of organs arranged as a long tube that works together to process foods

  • Mouth → anus

    • 1) Mouth 

    • 2) Esophagus

    • 3) Stomach

    • 4) Small intestine

    • 5) Large intestine

  • Accessory organs

    • Salivary glands, liver, pancreas, gallbladder

Digestion

• The process by which food is broken down into absorbable units to release nutrients

• Ingestion does not ensure absorption, when in the GI tract, nutrients are OUTSIDE the body

• 2 types of digestions: 

  • Mechanical

  • Enzymatic (chemical) 

• Enzyme = molecules that catalyzes chemical reaction

Circulatory System

Permits blood and lymph circulation

• Lymph contains white blood cells but no red blood cells

  • Ex: liquid in a blister is lymph

• Lymphatic system works with blood circulation system

Small Intestine

Major site of digestion and absorption

• Digestion of carbohydrates, fats, proteins

• Vitamins and minerals do not need digestion

• Nutrients are absorbed into either capillaries (blood) or lacteals (lymph)

About 20 feet long → folds all along the inside with finger like structures (villi) lining the walls/ folds with more finger like structures on each one (microvilli)

Divided into: duodenum, jejunum, ileum

Villi are tiny finger-like projections in the small intestine that increase the surface area for absorption, allowing for more efficient nutrient uptake

• Each villus is covered with even smaller projections called microvilli that provide the absorptive surfaces that allow nutrients to pass through to the body

• Microvilli and villi increase the contact surface between chyme and GI cells

Secretions of the small intestine

1. Mucus by goblet cells -→ protects lining of small intestine from the acidity of the chyme

2. Digestive enzymes that finish the digestion of carbs, fats, and proteins

3. Hormones → Gastric-inhibitory peptide, secretin, CCK

Hormones

• Gastric-inhibitory peptide → produced when chyme enters small intestine

  • Slows stomach secretions so that chyme isn’t released all at one time

  • Slows GI motility

• Secretin → produced when chyme enters small intestine

  • Stimulates pancreatic secretions

• Cholecytokinin - CCK → produced when fat/proteins enters small intestine

  • Stimulates gallbladder to release bile and pancreatic secretion

  • Slows GI motility

  • Reduces food intake

Secretions INTO small intestine

• Pancreatic secretions

  • Digestive enzymes → digestion of carbs, fats, proteins

  • Sodium bicarbonate → neutralizes acidic chyme

• Liver and gallbladder = bile

  • liver makes bile

  • gallbladder concentrates and stores bile

  • bile aids to digest lipids (fat)

Digestion

• Mechanical

  • Peristalsis (muscle contraction) pushed food through small intestine

  • Segmentation mixes chyme with digestive juices and breaks up food mass into smaller masses

    

• Chemical/enzymatic

  • Pancreatic and small intestine enzymes digest carbs, fats, and proteins into absorbable units

Absorption

• Absorbed into capillaries → Blood takes nutrients to the liver for processing after absorption

  • Digested carbs and proteins

  • Minerals

  • Water soluble vitamins

• Absorbed into lacteals (lymph) → nutrients travel through lymph system to chest area where lymph and blood join, nutrients enter blood and travel to liver

  • non-water soluble or fat related

    • Digested fats

    • Fat soluble vitamins

    • Cholesterol

The End Products of Digestion

Nutrients need to be broken down into small units that can be absorbed

• Big unit → little unit

  • Protein → amino acids

  • Carbohydrate → monosaccharides

  • Fat → fatty acids

• If you don’t absorb it then you don’t get any calories from it

• Simple diffusion = water and small lipids

• Facilitated diffusion = water soluble vitamins

• Active transport = glucose and amino acids

Large Intestine (Colon)

Lower part of the intestine that is wider than the small intestine and has no villi

Digestion

• Nutrient digestion already complete

• Some digestion of fibers by bacteria

Absorption

• Water

• Sodium, potassium, chloride

• Vitamin K (produced by bacteria)

Elimination

• Feces pass from colon into rectum

• Rectum stores feces until excretion occurs

Liver

Liver = produces and stores “energy”

Nutrients in the liver

• Carbohydrates

  • Monosaccharides → glucose

  • Glucose → energy

  • Glucose ← → glycogen

• Lipids

  • Products of digestion → fatty acids

  • Fatty acids → energy

  • Fatty acids ← → triglycerides

• Proteins

  • Makes non-essential amino acids (AA)

  • Removes excess amino acids (AA) from blood

  • Removes ammonia (NH3) from blood

    • Makes other nitrogen-containing compounds (DNA, RNA)

    • Makes blood proteins such as clotting factors

Other functions of the liver

• Detoxifies alcohol, drugs and poisons; prepares waste products for excretion

• Helps break down red blood cells

• Stores most vitamins and many minerals

• Forms lymph

Digestive Problems

Gastroesophageal reflux disease (GERD) → heartburn

• Stomach contents re-enter esophagus

• Treatment

  • Smaller meals, no food 3 hours before bed

  • Elevate head of the bed, use of antacids

Celiac disease

• Allergy to gluten

  • Gluten = protein found in wheat, barley, rye

  • Antibodies are released and attack microvilli → GI inflammation

• Managed by gluten-free diet

  • No wheat, rye, barley

Irritable Bowel Syndrome (IBS)

• Affects 20% of Americans

• Inflammation of the GI tract

• Cramps, gassiness, bloating, irregular bowel function

• Treatment

  • Elimination diet → eliminate foods that cause symptoms from the diet

  • Moderate caffeine intake

  • Favor low fat foods and small meals

  • Stress reduction

Constipation- hard, dry, infrequent stools that can be reduced by high fiber, intake, exercise

Diarrhea

• Loose, watery, frequent stools

• Symptom of diseases/infections

• Can cause dehydration

Diverticulosis

• “Pouches” along colon

• High fiber diet reduces formation

Review

MODULE 3: CARBOHYDRATES AND ALCOHOL

What we already know about carbs

Carbs

• Organic nutrient

• Mono and polysaccharides

• 4 kcal/g

• Found in fruits, vegetables, grains, and “sweets”

Digestion and absorption

• Digestion starts in the mouth (salivary amylase)

• Not much happening in the stomach

• Digestion continues in the small intestine

• Fibers are digested by bacteria in the large intestine

• Absorbed in capillaries (monosaccharides) via active transport

Where do carbs come from

Plats convert the sun’s energy into carbohydrates by photosynthesis

• Converting light energy from the sun into chemical energy stored in carb molecules

  

Simple vs Complex Carbohydrates

Carbs are composed of carbon, hydrogen, and oxygen (CHO)

• Each units contain 6 carbon atoms, 12 hydrogen atoms, 6 oxygen atoms (C6H12O6)

Simple carbohydrates

• Monosaccharides: one unit

• Disaccharides: two units

• their name ends in -ose

• Mono- and disaccharides are also called

Complex carbohydrates

• Polysaccharides: long chain on units

• Dietary fibers are polysaccharides

Simple Carbohydrates = sugars

Monosaccharides- single sugar unit

• Glucose

  • found in fruits, vegetables, honey

  • “blood sugar” → used for energy

• Fructose

  • Found in fruits, honey, corn syrup

  • “fruit sugar”

• Galactose

  • Found as part of lactose in milk

Disaccharides- two linked monosaccharide units

• Sucrose = glucose + fructose

  • “table sugar”

  • made from sugar cane and sugar beets

• Lactose = glucose + galactose

  • “milk sugar”

  • found in milk and dairy products

• Maltose = glucose + glucose

  • Found in germinating cereal grains

  • Product of starch breakdown

Complex Carbohydrates

Polysaccharides

• 2 types of complex carbs

  • Digestible

    • Starch- long chains of glucose units

      • Amylose- straight chains

    • Glycogen- highly branches chains of glucose units

      • Body’s storage form of carbohydrates in liver and muscles but undetectable in meat

  • Non-digestible

    • Dietary fiber- cannot be digested so 0 kcal/g

    • bacteria can digest some of them

    • Chains of monosaccharides

      • Short chains (oligosaccharides)

      • Long chains

Dietary Fibers

• Soluble fibers

  • Dissolves in water and is fermented by intestinal bacteria → can be digested by bacteria in the colon

  • Found in oats, legumes (dried peas and beans)

    • Ex: pectin in fruits and vegetables

  • Lowers blood and cholesterol

  • Control blood glucose

• Insoluble fibers

  • Do not dissolve in water

  • Found in bran of whole grains, seeds, vegetables

    • Ex: cellulose, hemicellulose, lignins

  • Increases GI transit

  • Prevents constipation

• Most plant food contain soluble and insoluble fibers

Carbohydrates Consumption, Digestion, and Absorption

Consumption

• Populations of the world derive more then ½ of their nutrients from carbohydrate foods

  • Easy to grow

  • Highly palatable (=good)

  • Can be stored for reasonable periods → Classic examples: rice, corn, wheat, potatoes, oats

• Most desirable form of energy for body

  • In form of glucose

  • Brain and red blood cells especially rely on glucose for fuel source

Digestion

• Begins in the mouth → salivary amylase begins digestion of starch

• Digestion slows in the stomach

• Digestion resumes in small intestine

  • Pancreatic amylase (secreted by pancreas)

    • Starch digestion to disaccharides

  • Brush border enzymes (secreted by small intestine)

    • Digest disaccharides to monosaccharides

Absorption

• End products: monosaccharides

  • Glucose, fructose, galactose

  • Absorbed by active transport

• Absorbed into bloodstream then processed in the liver

• Are converted to glucose (for galactose and fructose) in the liver

• Fibers are not digested

Use of Glucose

Glucose is the main source for energy for your body

Blood glucose levels must be maintained

Adequate glucose levels → where does the extra glucose go?

1. Storing glucose as glycogen → when we have adequate carbohydrate from diet, liver stores extra as glycogen

2. Converting glucose to fat → when we have excessive carbohydrate, and glycogen stores are filled, will store extra as body fat

Inadequate glucose supply → where do we find glucose

• Glucose blood levels must be maintained

• Short term → making glucose from glycogen

  • Blood glucose come from breakdown of liver glycogen

  • This pathway will be used when fasting for short time (ex: sleeping)

• Long term → making glucose from protein

  • Blood glucose comes from breakdown of muscle (protein)

  • This pathway will be used when there is not enough dietary glucose (ex: low carb diet)

  • Byproduct of muscle breakdown is NH3 (ammonia) excrete through the kidneys as urea

  • This stresses the kidneys

When there is inadequate carbohydrates in the diet, the has 2 problems

• Having no glucose, the body turns to protein to make some glucose

  • breakdown of muscle

  • Kidney stress

• Without carbohydrates in the diet, fat cannot be used correctly for energy, and the body converts its fats into ketone bodies

  • Glucose can be stored into fats, fats can not be used to make glucose

• Glucose = sugar used by body for energy

• After digestion monosaccharides are converted to glucose in the liver

  • When there is enough glucose the rest is stored as glycogen

  • When glycogen stores are full its going to be stored as fat

• When blood glucose levels are low we need more glucose → first we make it from glycogen

  • Glucose cannot be made from fat

• When all glycogen is depleted, protein will be used to make glucose → breakdown of muscle and causes stress to kidneys

Break down of glucose provides energy

Hormonal Regulation of Blood Glucose

Insulin and glucagon are 2 hormones involved in regulating blood glucose (glycemia)

• Insulin triggers storage of glucose as glycogen

• Glucagon triggers glycogen break down to release glucose

• Both of these are secreted by the pancreas and release depends on blood glucose

Eat a meal

• Increase blood glucose (high BG)

• High BG increases insulin release from pancreas

• Insulin decreases BG by letting glucose into tissues/organs

When fasting

• Low BG

• Low BG increase glucagon release from pancreas

• Glucagon increases BG by breaking down glycogen

Diabetes

Diabetes Mellitus- persistent high blood glucose levels

• Type 1: lack of insulin production (immune disease)

  • Own immune system attacks pancreas

  • Treat with insulin (insulin-dependent)

• Type 2: liver cells are resistant to insulin

  • Treat with diet and exercise

  • May treat with oral medications

  • May treat with insulin

Type 2 diabetes and obesity

• Type 2 diabetes- predominant type of diabetes

  • Lose sensitivity to insulin

  • Obesity underlies many cases

  • other factors foreshadowing development

    • Middle age and physical inactivity

    • Body fat accumulation

    • Genetic inheritance

Management of Diabetes

• Controlling blood glucose is key

  • Monitoring blood glucose levels (glucometer)

  • Taking medications → insulin injections if needed

• Type 2: controlling body fatness

• Establish good/regular eating patterns

• Diet adaptation

  • Carbohydrates timing

    • If insulin injection are used, injections and carbs intake must be timed

  • Artificial sweeteners

Hypoglycemia

Abnormally low blood glucose

• Rare, but true disease

Postprandial hypoglycemia

• Hypoglycemia following a meal

• Requires test to detect

Fasting hypoglycemia

• Hypoglycemia when food is not consumed for a while

Methods to reduce symptoms

• Eat frequent meals

• Avoid “sugars load”

Glycemic Effects of Foods

Glycemic index affected by

• Type of carbohydrates (simple sugars increase glycemic index)

• Cooking process

• Presence of fat or fiber (decrease glycemic index)

Glycemic index of foods not always easy to predict

• Ice cream has low index due to fat content

• Bread and potatoes have high index because starch is quickly digested

% as compared to glucose (=100%)

• Angel food cake: 67

• Waffles: 76

• White bread: 70

• All Bran: 42

• Corn Flakes: 84

• Instant rice: 91

• Ice cream: 61

• Skim milk: 32

• Pineapple: 66

• Black-eyed peas: 42

• Spaghetti: 41

• Carrots: 71

• Baked potatoes: 85

• Green peas: 48

  

Carbohydrates and health

High sugar (mono/disaccharides) intake

• Low nutrient contents

• Contributes to tooth decay

• If excess kcal, contributes to obesity

High fiber intake

• Reduce blood cholesterol

• Reduced risk of heart disease

• Healthier GI functioning

Carbohydrates in your diet

• Recommended carbohydrate intae

  • 45-65% of kilocalories

  • Daily Value (for 2,000 kcal) = 300 grams

• Dietary guidelines for carbohydrates

  • Make half of your grains whole grains

  • Choose and prepare foods and beverages with little added sugars

• Recommended fibers intake (Daily Value 2000 kcal diet)

  • 38 grams for men

  • 25 grams for women

• Dietary guidelines for carbohydrates

  • Make half your grains whole grains

  • Choose and prepare foods and beverages with little added sugars

Nutrients in bread

• Whole grains contain more nutrients than refined grains

• Make half of your grains whole grains

Sugars

• Mono and disaccharides

  • Rapidly absorbed

  • Raise blood glucose

  • Can contribute the kcal overload

• Sugars are however commonly used as an additive, they can:

  • Enhance flavor

  • Provide fuel for fermentation (bread, beer, wine)

  • Act as a preservative (jams)

  • Balances acidity of tomato and vinegar-based products

Natural vs added sugars

• Natural sugars

  • Naturally occurring sugars found in fruits and dairy

  • Usually more nutrient dense

• Added sugars

  • Sugars are added by manufacturers

  • Often “empty calories” or “discretionary” calories

  • Ex: soda, candy

Sugars - recommended intake

• DGA 2026: “… reduce the intake of kcals from added sugars to no more than 10% each day”

  • The average American adult gets ~300 calories of added sugars each day… 18 tsp of sugar

  • Added sugars contribute calories, but not essential nutrients

High- Fructose Corn Syrup (HFCS)

• HFCS is made through an enzymatic process which converts half of the glucose in corn syrup into fructose to increase the sweetness of the syrup

• It is the principal sweetener used in processed foods and beverages - because it is cheaper

• The effect on increase in obesity has not been proven

• Effects on lipid metabolism

  • Fructose causes fats to accumulate in blood and liver

• Appetite regulation

  • Fructose does not stimulate insulin release

Alternative Sweeteners

• Advantages

  • Sweetness without the calories

  • Better for your teeth

• Disadvantages

  • Flavor may not be quite right (bitter, metallic aftertaste)

  • Does’t act the same in food

  • Sugar alcohols can cause intestinal distress

  • $

Aspartame

• Acceptable Daily Intake

  • Defined as the amount of a food additive that can be safely consumed on a daily basis over a person’s lifetime without any adverse effects

  • Accepted daily intake: 50 mg/kg/body weight/day

  • Average consumption in the US is 2-4 mg/kg/day

  • 200 mg aspartame per 12 oz diet soda

Phenylketonuria

• Phenylketonuria (PKU) is a metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase. This enzyme is necessary to metabolize the amino acid phenylalanine

• Untreated PKU can lead to mental retardation, seizures, and other serious medical problems

• The mainstream treatment for classic PKU patients is a strict PHE-restricted diet supplemented by a medical formula containing amino acids and other nutrients. 

• Aspartame contains phenylalanine