Human Nutrition 2002 - Sections 4-7

Food Pattern

What an individual eats and drinks on a regular basis.Does not focus on individuals food or drinks.

Discretionary Calorie Allowance

The difference between the calories needed to maintain weight and those needed to supply nutrients. Gives people the option to choose some less nutrient-dense foods they may desire.

Why Do We Need a Healthy Eating Strategy?

Poor diets lead to chronic disease. It is difficult to eat well due to the abundance of cheap food backed by powerful marketing machines. Too many Canadians are overweight or obese and have chronic diseases.

The Healthy Eating Strategy Include

Better nutrition guidance through a modernized Canada’s Food Guide, Improved food lables and FOP labelling to help Canadians make informed food choices, Improved food quality (less sodium, no industrially produced trans fat), Protected vulnerable populations, by restricting marketing of unhealthy foods and beverages to children, and better food access through an improved Nutrition North Canada program.

Major Generational Shift in Translation Dietary Guidance

Tools, Proportions vs. Servings, Change in food groups, Protein foods.

Food Guide Changes Related to "Food Groups"

Shift away from "meat and alternatives" to "Eat protein foods", with emphasis on plant proteins. "Milk and alternatives" have become part of "Eat protein foods". Overall shift towards a more plant-based diet.

Discretionary Calorie Allowance Options

1. Extra servings of nutrient-dense foods at diet's base

2. Fats - Foods higher in naturally occurring fats and added fats

3. Added sugars (jams, colas, honey)

4. Alcohol within limits

5. Omit discretionary calories for weight loss

(Physical activity affects an individual's discretionary

Calorie allowance).

The Three Food Groups on Canada's Food Guide are

1. Vegetables and Fruits

2. Whole Grain Foods

3. Plant and Meat-based Protein Foods

Digestive Tract

Flexible, muscular tube. Extends from the mouth through the throat, esophagus, stomach, small intestine, large intestine, and rectum to the anus. The total length is about 8 metres. The body surrounds the digestive canal.

The Primary Role of the Digestive Tract

Digest food to its components, absorb, and excrete.

Chewing and Swallowing

Salivary glands add water, minor digestive enzymes (for starch and fat), antimicrobial components, mucus - to form a smooth food bolus. The teeth crush food to increase the surface area, open up seeds, hulls, etc.

Mechanical Digestion

Begins in the mouth; aided by chewing, saliva. Stomach and small intestine. Peristalsis helps to liquefy food. Chyme/digesta help to create a paste-like substance.

Chemical Digestion

Digestive juices are secreted by salivary glands, stomach, pancreas, liver, and small intestine. Digestive juices contain enzymes that break down nutrients. Digestion begins in the mouth. Saliva contains enzymes that break down. Starches (salivary amylase). Fats (lingual lipase).

Protein Digestion

Begins in the stomach. Gastric juices (water, enzymes, hydrochloric acid) are required to activate the protein-digesting enzyme (pepsin). Acid strength is determined by its pH.

Small Intestine

The organ of digestion and absorption.

The Small Intestine Secretes the Following Fluids to Aid in Digestion

Bile and Pancreatic Juice.

Bile

Emulsifier, made by the liver, stored in the gallbladder.

Pancreatic Juice

Secreted by the pancreas, contains an acid-neutralizing agent.

Absorption

Nutrient molecules traverse intestinal lining cells. Cells absorb nutrients and deposit in blood (carbohydrate, protein, minerals, most vitamins) and lymph (fat, some vitamins). The cells of the small intestine are selective, increasing absorption of some nutrients that may be in short supply.

Absorption and Transportation

The digestive system is sensitive to malnutrition. Severe undernutrition will result in the shrinking of the absorptive surface of the small intestine. This causes impaired digestion, and the impaired digestion worsens malnutrition.

Large Intestine

Absorbs water. A few nutrients/metabolites are absorbed in the colon from bacterial activity.

A Notice from Your Digestive Tract

The body's response to - Eating or drinking too fast = hiccups, choking. Eating or drinking too much = heartburn, GERD. Treatment with antacids or acid reducers may aggravate the problem. Other digestive disturbances include constipation and diarrhea.

Five Basic Chemical Tastes

Sweet, sour, bitter,salty, and umami or savoury. Sweet, salty, and fatty foods are universally desired.

Swallowing Co-ordination Affected By

Diseases of the nervous system (e.g. Alzheimer's, Parkinson's), stroke, prematurity, etc.

The Healthy Digestive System

Capable of adjusting to almost any diet and can handle any combinations of food with ease. Within 24 to 48 hours, 90 percent of carbohydrate, fat, and protein are digested and absorbed.

The Rate at Which Nutrients are Absorbed Depends on Many Factors

The form of the nutrient in a food, Other nutrients or components within the food, The body's need for the nutrient, and the health of the GI tract.

Details of the Small Intestinal Lining

The cells of the intestinal tract lining are arranged in sheets that poke out into millions of finger-shaped projections (villi). Every cell on every villus has a brush-like covering of tiny hair-like projections (microvilli) that can trap the nutrient particles. Each villus (projection) has its own capillary network and a lymph vessel so that nutrients move across the cells.

Glycerol

A small, water-soluble carbohydrate derivative, plus three fatty acids, equals a triglyceride.

Linolenic Acid

An omega-3 fatty acid.

Linoleic Acid

An omega-6 fatty acid.

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 saturated the fatty acids, the firmer the fat is at room temperature.

Unsaturated Fatty Acid

Points of unsaturation are places on fatty acid chains where hydrogen is missing. The bonds that would normally be occupied by hydrogen in a saturated fatty acid are shared, reluctantly, as a double bond between two carbons that both carry a slightly negative charge.

Hydrogenated Fatty Acid (fully saturated)

When a positively charged hydrogen is made available to an unsaturated bond, it readily accepts the hydrogen and, in the process, becomes saturated. The fatty acid no longer has a point of unsaturation.

Trans Fatty Acid

The hydrogenation process also produces some trans fatty acids. The trans fatty acid retains its double bond but takes a twist instead of becoming fully saturated. It resembles a saturated fatty acid both in shape and in its effects on health.

Interesterification

Replacement of the partial hydrogenation process. Specific positional composition and/or functionality. Used to produce hard stock fats.

Fat or Lipid

Class of naturally occurring organic compounds which are generally hydrophobic in nature. Various types include fatty acids, triacyglycerides, sterols and phospholipids.

Fatty Acids

Carboxylic acid with aliphatic carbon chain. Common lengths - C4 - C28.

Triglycerides

Most abundant dietary lipid. Consist of 3 fatty acids and 1 glycerol molecule.

Phospholipids

Amphipathic and major lipid found in biological membranes. Consists of 2 fatty acids, glycerol, phosphate group and organic molecule.

Sterols

Amphipathic lipids with hydroxyl group - alcohols. Conserved 4 ring structure.

Omega-6

Linoleic Acid - Leafy vegetables, seeds, nuts, grains, vegetable oils (corn, safflower, soybean, canola, cottonseed, sunflower).

Omega-3

A Linolenic acid (ALA)- Fats and oils (canola, soybean, walnut, wheat germ, margarine and shortening made from canola and soybean oil. Nuts and seeds (walnuts, soybean kernels. Vegetables.

EPA and DHA

Human milk (levels depend on mother's status and intake), Omega-3 milk beverage, Fatty cold-water fish (mackerel, salmon, bluefish, mullet, sablefish, menhaden, anchovy, herring, lake trout, sardines, tuna), Omega-3 eggs.

Why Do We Need Dietary Fat?

An important source of food energy (needs change through the life-cycle). Provides and enables the absorption of fat soluble vitamins (A, D, E & K). Provides the essential fatty acids. Makes food palatable - dissolves flavors and has a characteristic mouth-feel. 

Points to Consider

Amounts required to meet needs for energy, fat-soluble vitamins, and essential fatty acids requirements. Also consider the amounts required to decrease risk of chronic disease.

The more carbon atoms in a fatty acid

The longer it is. The more hydrogen atoms attached to those carbons, the more saturated the fatty acid is.

The Three Types of Fatty Acids:

1. Saturated

2. Monounsaturated

3. Polyunsaturated

Alternatives to Partial Hydrogenation

Full hydrogenation, fractionation, and highly saturated traditional fats. Interesterification of blends of fractionated and/or fully hydrogenated fats.

Fat as a Source of Energy

Fat provides 9 kcal/g (37kJ/g) compared with ~4 kcal/g for protein (18kJ/g) and carbohydrate (17kJ/g). 

% energy from fat = (fat in g x 9) / total energy intake in kcal) *100

Cholesterol is only found in animal products. 

Fats in the Body

• Energy stores - Fats are the body's chief form of stored energy.

• Muscle fuel - Fats provide most of the energy to fuel muscular work.

• Emergency Reserve - Fats serve as an emergency fuel supply in times of illness and diminished food intake.

• Padding - Fats protect the internal organs from shock through fat pads inside the body cavity.

• Insulation - Fats insulate against temperature extremes through a fat layer under the skin.

• Cell Membranes - Fats form the major material of cell membranes.

• Raw Materials - Fats are converted to other compounds, such as hormones, bile, numerous bioactive compounds, and vitamin D, as needed.

Fats in Food

• Nutrient - Fats provide essential fatty acids.

• Energy - Fats provide a concentrated energy source in foods.

• Transport - Fats carry the fat-soluble vitamins A, D, E, and K along with some phytochemicals and assist in their absorption.

• Raw Materials - Fats provide raw material for making needed.

• Sensory Appeal - Fats contribute to the taste and smell of foods.

• Appetite - Fats stimulate the appetite.

• Satiety - Fats contribute to feelings of fullness.

• Texture - Fats help make foods tender.

Dietary Fat Recommendations

• < 30% of energy from fat (2000 kcal diet this is > 65g / day)

•  ≤ 7% of energy from saturated (+ trans)

• ≥ 10% polyunsaturated

• ≥ 13% monounsaturated

• <300 mg cholesterol / day

How to Meet Recommendations

• Choose foods with lower fat.

• Eat less animal fat, particularly those from red meats, replace with poultry and fish.

• Eat less hydrogenated fat, less processed foods.

Protein

A polymer of amino acids. 20 amino acids in protein. 9 are essential: that is they are not synthesized in the body and therefore must be provided by dietary proteins. All 20 amino acids must be present at the same time for protein synthesis to take place.

Protein Turnover

All proteins, esp from short lived cells. 300-400 g / day turnover, consuming ~20% of energy needs ~25% is lost irreversibly, so required from diet. Higher if growing, healing, stressed, etc. No storage!

Acid-base balance

Proteins help maintain the acid-base balance of various body fluids by acting as buffers.

Antibodies

Proteins form the immune system molecules that fight diseases.

Blood clotting

Proteins provide the netting on which blood clots are built.

Energy

Proteins provide some fuel for the body's energy needs.

Enzymes

Proteins facilitate needed chemical reactions.

Fluid and electrolyte balance

Proteins help maintain the water and mineral composition of various body fluids.

Growth and maintenance

Proteins form integral parts of most body tissues and serve as building materials for growth and repair of body tissues, such as skin, connective tissues, muscles, organs, and bone.

Hormones

Proteins regulate body processes. Some hormones are proteins or are made from amino acids.

Transportation

Proteins help transport needed substances, such as lipids, minerals, and oxygen, around the body.

Vision

Various proteins called opsins are important for both colour and night vision.

Dietary Protein (Amino Acids)

Dietary protein is nutritionally essential to provide amino acids and nitrogen for the synthesis of body proteins and other nitrogen-containing molecules. The quality of dietary protein will affect one's protein requirement, because protein requirement really means amino acid requirements.

Protein Quality

How well does a dietary protein supply the essential amino acids. Determined by - Pattern of essential amino acids (Generally animal > plant) and Digestibility - how well is the protein digested and the amino acids absorbed (Generally animal > plant), (Cooked > raw).

"High quality" protein

All essential (indispensable) AA in amounts needed by humans. Mostly animal origin - Exceptions: soy protein (high lys) and gelatin (low trp). 

"Low quality" protein

Plant foods - Legumes, vegetables, cereals, grains. Too little of one or more indispensable AA. "Limiting AA". Careful planning needed to ensure protein synthesis.

The concept of first limiting amino acid

"Staves" represent percent of requirement. Water level is protein synthesized.

Pulses

Part of the legume family (any plants whose seeds grow in pods), but the term refers only to the dry edible seed within the pod. Beans, lentils, chickpeas, and split peas are the most common types of pulses. Peanuts, soya beans, and fresh beans and peas are legumes butare not considered pulses.

Omnivore

Includes food of both plant and animal origin, including animal flesh.

Fruitarian

Includes only raw or dried fruit, seeds, and nuts in the diet.

Lacto-ovo Vegetarian

Includes dairy products, eggs, vegetables, grains, legumes, fruit, and nuts; excludes flesh and seafood.

Lacto-vegetarian

Includes dairy products, vegetables, grains, legumes, fruit, and nuts; excludes flesh, seafood, and eggs.

Macrobiotic Diet

A vegan diet composed mostly of whole grains, beans, and certain vegetables; taken to extremes, macrobiotic diets have resulted in malnutrition and even death.

Ovo-vegetarian

Includes eggs, vegetables, grains, legumes, truit, and nuts; excludes flesh, seafood, and milk products.

Partial Vegetarian

A term sometimes used to mean an eating style that includes seafood, poultry, eggs, dairy products, vegetables, grains, legumes, fruit, and nuts; excludes or strictly limits certain meats, such as red meats.

Pesco-vegetarian

Same as partial vegetarian but eliminates poultry.

Vegan

Includes only food from plant sources - vegetables, grains, legumes, fruit, seeds, and nuts; also called strict vegetarian.

Vegetarian

Includes plant-based foods and eliminates some or all animal-derived foods.

What happens to amino acids once they are absorbed?

1. Used to build proteins (and re-build). 

2. Converted to other small, nitrogen containing compounds, e.g., thyroid hormone, serotonin. 

3. Converted to other amino acids, synthesis of the non-essential amino acids.

4. Once the nitrogen is removed metabolically -

A) Converted to glucose, some but not all amino acids can do this.

B) Burned as fuel.

C) Converted to fat. 

Essential Amino Acids

Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.

Sources of Protein from Food Intake Data

• Meat, fish, poultry - 40.8%

• Cereals - 20.5%

• Dairy Products - 22.3%

• Beans, nuts, peas, etc. - 3.2%

• Fruits and Vegetables - 8.1% (vegs 6.4, fruit 1.7)

• Eggs - 4.1%

Note: quality animal > plant. Digestibility animal > plant, cooked > raw

How much protein do you need?

1. For "normal" adults, need 0.8 g protein / kg body weight / d

• Note that average intake of protein in Canada is 1.5 to 2 X the RDA

• For females, RDA 46 g/ d, typical intake 65g / d.

• For males, RDA 56g/ d, typical intake 105g/ d.

• If you eat enough calories, you're eating enough protein

2. Depends on Quality and Digestibility

• Animal> Plant (less important in mixed diet)

How much protein do you need?

3. Increased needs for special situations, e.g.

a) Growth / repair

b) Inadequate energy intake

c) Pregnancy / lactation

d) High intensity / long duration aerobic exercise. May need 1.2 - 1.8 g / kg, or ~ 2X RDA

e) Body builders "finishing" for a competition. Typically eat a low calorie diet so protein need is increased because using protein for energy and maintenance / growth.

4. Protein undernutrition

Marasmus

Kwashiorkor

a) Marasmus/Kwashiorkor (developing world)

b) Extreme diets, wasting diseases, elderly, food insecurity

5. Excess?

a) Probably, but little evidence in healthy adults

Protein foods are good for you

You can eat a variety of protein foods as part of a healthy eating pattern. Protein foods have important nutrients such as - 

• Protein

• Vitamins

• Minerals

Choose protein foods that come from plants more often. Plant-based protein foods can provide more fibre and less saturated fat than other types of protein foods. This can be beneficial for your heart health.