Human Nutrition

Digestive System

Nutrients:Utilized or Stored Until Needed

Food Guide Pyramid

Diet and regular exercise

Nutrition - MacronutrientsCarbohydrates: major energy source,

simple or complex. Metabolic rate related to glycemic index

Lipids: cell components and energy sources, saturated or unsaturated, transfats, omega oils

Proteins: 20 natural amino acids, building and repair, hormones, enzymes

Water: solvent, thermoregulation, metabolic processes

Nutrition - Micronutrients

Vitamins: fat soluble and water solubleMinerals: recommended daily allowance

(rda)Fiber: some evidence decreases colon

cancer

Carbohydrates

General formula ratio is for most carbohydrates is CH2O

Carbohydrate rich foods in their natural state are low in calories and high in fiber (AKA as cellulose, plant fibers we do not digest).

Carbohydrates contain about 4 calories per gram (fats about 9 cal per gram).

Simple Carbohydrates

Also called simple sugars. Simple carbohydrates include

monosaccharides and disaccharides such as: fructose (fruit sugar), sucrose (table sugar) and lactose (milk sugar), as well as several other

sugars.

Simple carbohydrates are sources of quick energy.

Complex Carbohydrates

Complex carbohydrates include fiber and starches.

Found in vegetables, bread, rice, oatmeal, whole grains, peas and beans.

Meats also provide carbs in the form of glycogens.

Complex Carbohydrates

Complex carbohydrates take longer to be digested, so your body needs more time to release these carbs into your blood as glucose.

This results in sustained energy (stamina). SEE GLYCEMIC INDEX

Undigestible Complex Carbohydrates

Also called fiber Essential role in large

intestine health “Brushes” walls of

large intestine

Carbohydrates • When we eat carb rich foods, our blood

glucose levels increase dramatically. • our pancreas secretes insulin so that

glucose units can be taken into body cells for use in respiration (producing ATP).

• Insulin and diabetes

Blood Sugar

• In times of not eating, our brain still needs glucose, our muscles still need glucose

• This stimulates the pancreas to produce the hormone glucagon which converts glycogen stored in the liver into glucose.

• If there is still insufficient glucose, the liver metabolizes fats and converts these molecules into glucose.

Glucose to Glycogen

Glycemic Index

High glycemic foods are used quickly and stored as fat tissue easily.

Low glycemic foods provided more long term energy and reduced insulin levels (which is a good thing).

Glycemic Index

The effect of eating high glycemic index foods consistently is to lead to constantly high insulin levels.

In this situation, the body becomes accustomed to these high insulin levels and starts to respond to them less effectively over time.

Glycemic Index

As high glycemic index foods are eaten further, this progresses, more and more insulin is required to have the same effect on the tissues.

This phenomenon is known as insulin resistance, and is the first step towards diabetes.

Glycemic Index

Highglycemic index

Mediumglycemic index

Lowglycemic index

Maltose (beer)* Rye bread (crispbread) Oatmeal porridge

Cooked parsnips Muesli (no sugar) Wholewheat pasta

Cooked carrots Brown rice Sweet potato

White Rice Cooked beets Dried Peas

Biscuits / cookies Garden peas Apples

Baked potato Boiled potato Pears

Cornflakes / cereal Wholewheat bread Whole milk

Bagels Corn, polenta Kidney beans

White Bread Sultanas / raisins Lentils

Corn chips Orange juice Soybeans

Mangoes Oatmeal biscuits / cookies High water content fruits (melon etc)

Ripe bananas White pasta Apple juice

Papaya Buckwheat black-eye peas

Rice cakes Pinto beans Green vegetables

Lipids

Triglycerides have the general elements are C, H, O like carbs except they have much less O. They are made of glycerol and fatty acids.

Glycerol is a small, 3-carbon molecule with three hydroxyl groups.

Lipids

Fatty acids are long molecules with a polar, hydrophilic end and a non-polar, hydrophobic "tail". The hydrocarbon chain can be from 14 to 22 CH2 units long *even number of C.

Saturated Fats

If there are no C=C double bonds in the hydrocarbon chain, then it is a saturated fatty acid (i.e. saturated with hydrogen).

These fatty acids form straight chains, and have a high melting point.

Sources are animals: butter and lard (solid at room temp.)

Unsaturated Fats

If there are C=C double bonds in the hydrocarbon chain, then it is an unsaturated fatty acid (i.e. unsaturated with hydrogen).

These fatty acids form bent chains, and have a low melting point.

Unsaturated Fats

Fatty acids with more than one double bond are called poly-unsaturated fatty acids (PUFAs).

Cold blooded animals (fish) and plants are sources: omega fatty acids, flax, olive oil, canola and sunflower oil.

Triglycerides

Triglycerides are insoluble in water. They are used for storage, insulation and

protection in fatty tissue (or adipose tissue) found under the skin (sub-cutaneous) or surrounding organs.

They yield more energy per unit mass than other compounds so are good for energy storage (about 2X more energy).

DIETARY CONSIDERATIONS

In food chemistry, HYDROGENATED margarine is plant unsaturated fatty acid which has had H added back to its structure.

This results in a margarine which is more solid and able to with-stand higher temperatures.

Most unsaturated fats are liquids (olive oil, canola oil are liquid at room temperature).

DIETARY CONSIDERATIONS

TRANS FATS: Unsaturated fats have a structure with kinks; these kinks result in a liquid state at room temperature.

In the early 20th century, a chemical process called hydrogenation was developed that converts vegetable oils into saturated, more solid fats (margarine and vegetable shortening).

DIETARY CONSIDERATIONS

When it was discovered that eating saturated fats increases the risk for coronary heart disease, the food industry turned to partial hydrogenation.

This process lowered the content of saturated fat in vegetable shortening and margarine, but also dramatically increased the amount of a certain kind of fat - trans fat - in our diets, as an unavoidable side reaction.

DIETARY CONSIDERATIONS

While suppliers praised processed vegetable oils as healthy unsaturated and cholesterol-free substitutes for animal fats, there is now strong evidence that introducing trans-fatty acids into our diets does more harm than good.

Phospholipids

Phospholipids have a similar structure to triglycerides, but with a phosphate group in place of one fatty acid chain.

There may also be other groups attached to the phosphate.

Phospholipids

Phospholipids have a polar hydrophilic "head" (the negatively-charged phosphate group) and two non-polar hydrophobic "tails" (the fatty acid chains).

This mixture of properties is fundamental to biology, for phospholipids are the main components of cell membranes.

Waxes

Waxes are formed from fatty acids and long-chain alcohols.

They are commonly found wherever waterproofing is needed, such as in leaf cuticles, insect exoskeletons, birds' feathers and mammals' fur.

Waxes - Cholesterol

CHOLESTEROL is like a fatty wax. Normally made in the liver, it is structural component of nerve tissue and cell membranes.

It is also used to make various steroid hormones including progesterone, testosterone (sex hormones in females and males) estradiol, and cortisol.

Bile salts are breakdown products of cholesterol.

Waxes

Blood is watery, and cholesterol is fatty. Just like oil and water, the two do not mix.

To travel in the bloodstream, cholesterol is carried in small packages called lipoproteins.

The small packages are made of fat (lipid) on the inside and proteins on the outside.

Two kinds of lipoproteins carry cholesterol throughout your body.

Waxes

It is important to have healthy levels of both:

Low-density lipoprotein (LDL) cholesterol is sometimes called bad cholesterol.

High amounts of LDL cholesterol leads to a build up of cholesterol in arteries.

The higher the LDL level in your blood, the greater chance you have of getting heart disease.

Waxes

These form plaques along arteries. When it hardens the arteries we call it

arteriosclerosis. These can dislodge to plug smaller arteries

or veins—heart attacks or strokes are possible.

They can completely block a vessel resulting in an embolism, aneurism, heart attack, stroke.

Waxes

Waxes

High-density lipoprotein (HDL) cholesterol is sometimes called good cholesterol.

HDL carries cholesterol from other parts of your body back to your liver.

The liver removes the cholesterol from your body.

The higher your HDL cholesterol level, the lower your chance of getting heart disease.

The cholesterol numbers:

Things that TEND to increase LDL levels:

Overweight Physical inactivity• Cigarette smoking Excessive alcohol use Physical inactivity Very high carbohydrate diet Certain diseases and drugs Genetic disorders.

What seems to be the population trend:

Proteins

The polymer of amino acids does not remain like a long chain but folds into a three-dimensional shape which is the most stable for that sequence of amino acids.

This shape is called the native conformation for that particular protein and is essential for that protein's biological activity. i.e. shape is everything

Proteins

The shape may be altered by various factors e.g. heat or large pH changes.

Once the three-dimensional shape is altered, biological activity is lost.

The building blocks of proteins are amino acids

These are arranged in a very specific order – determines shape

Essential & Non-Essential AA’s

As far as your body is concerned, there are two different types of amino acids: essential and non-essential. Non-essential amino acids are amino acids

that your body can create out of other chemicals found in your body.

Essential amino acids cannot be created, and therefore the only way to get them is through food.

Protein

Protein in our diets comes from both animal and vegetable sources. Most animal sources (meat, milk, eggs) provide what's called "complete protein," meaning that they contain all of the essential amino acids.

Vegetable sources usually are low on or missing certain essential amino acids. For example, rice is low in isoleucine and lysine.

Balancing AA’s

However, different vegetable sources are deficient in different amino acids, and by combining different foods you can get all of the essential amino acids throughout the course of the day.

This balancing of amino acids is essential because if one amino acid is deficient, an entire protein cannot be made sufficiently.

Vegetarian Diets

Vegetarians need to balance plant source proteins—eg. Rice with beans.

Some vegetable sources contain quite a bit of protein -- things like nuts, beans, soybeans, etc. are all high in protein. By combining them you can get complete coverage of all essential amino acids.

Types of Vegetarian Diets

Pescatarian – may include fish but no chicken, beef, pork

Flexitarian – may include some meat time to time

Lacto-Ovo vegetarian – includes milk products and eggs but no meats

Vegan – do not include any animal products including processed foods that may include animal products like gelatine, honey.

The digestive system breaks all proteins down into their amino acids so that they can enter the bloodstream.

Cells then use the amino acids as building blocks.

To Get Protein RDA

This photo is the

Nutritional Facts label

from a can of tuna. According to the RDA (Recommended

Daily Allowance) for protein is 0.36 grams of protein per pound of body weight. So a 150-pound person needs 54 grams of protein per day.

From this you can see that your body cannot survive strictly on carbohydrates. You must have protein.

Nutritional label from a can of tuna fish You can see that a can of tuna contains

about 32 grams of protein (this can has 13 grams per serving and there are 2.5 servings in the can).

A glass of milk contains about 8 grams of protein.

A slice of bread might contain 2 or 3 grams of protein.

You can see that it is not that hard to meet the RDA for protein with a normal diet.

Role of Insulin

Insulin is a simple protein in which two polypeptide chains of amino acids are joined by disulfide linkages.It transfers glucose into cells to produce energy for the body. In adipose (fat) tissue, insulin facilitates the storage of glucose and its conversion to fatty acids.

Role of Insulin

• Insulin also slows the breakdown of fatty acids.

• In muscle it promotes the uptake of amino acids for making proteins.

Role of Insulin

In the liver it helps convert glucose into glycogen (the storage carbohydrate of animals) and it decreases gluconeogenesis (the formation of glucose from noncarbohydrate sources like fat or protein).

The action of insulin is opposed by glucagon, another pancreatic hormone, and by epinephrine.

If glucose levels remain high, the liver: stores the sugars as glycogen (animal

starch). If the glycogen is not used up, it further

metabolizes glycogen into fatty acids and fat molecules.

These are transported around the body in blood vessels and lymphatic vessels and is stored in ADIPOSE tissue (fat tissue) until needed.

If glucose levels remain high, the liver: This provides smoothness under the skin,

protection, and a secondary source of energy when needed—not all fat is bad.

If we don’t use it regularly though, it builds up into unhealthy situations such as fatty tissue around the heart and in the blood vessels. (Long Term Storage)

Disposal by Various Tissues of a Hypothetical Meal Containing 100 g of Glucose

http://www.medscape.com/infosite/diabetes_education/article-3

Extreme starvation situations (dieting)

After immediate energy sources are used (like carbohydrates—including stored glycogen converted to blood sugar), fat reserves are used.

After fat reserves are used, the body begins to “call-up” proteins. Proteins are converted into an energy source as a last resort.

Extreme starvation situations (dieting)

This is damaging to our protein rich tissues (muscles, hair, nails) and we notice the differences in our eyes, nails, hair and skin texture.

It also damages skeletal muscles and heart muscle. These damages are not easily reversed by “proper” dieting later.

PRIORITIZED SOURCES OF ENERGY

Sugars Fats Proteins This site slightly detailed metabolic

pathways that describe biochemical processes in metabolism:

http://users.humboldt.edu/rpaselk/BiochSupp/PathwayDiagrams/PathIndex.html

1991 study published in the "The American Journal of Clinical Nutrition"

Showed that patients following a very low-calorie diet lost lean body mass and experienced a

decrease in metabolic rate after only three days.

Then, 21 days after the start of the diet, participants experienced an 18 percent decrease in metabolism and lean body mass, on average.Read more: http://www.livestrong.com/article/486748-dieting-muscle-atrophy/#ixzz1eyOOO3A7

GENERAL PRINCIPLES OF WEIGHT CONTROL

Body weight is always the result of a simple equation. Input vs. Output = Body Weight

Input refers to the amount of food consumed.

Output refers to the amount of energy expended.

GENERAL PRINCIPLES OF WEIGHT CONTROL

Therefore, if Output = Input you will maintain your present weight.

If Input is less than Output you will lose weight. If Input is greater than Output you will gain weight.

There is no short cut to weight loss. One pound of body weight = 3,500 kcal

or 32,000kj.

GENERAL PRINCIPLES OF WEIGHT CONTROL

In order to reduce body weight you must do one of the following: Decrease food intake Increase activity Do a combination of both (this is most

effective)

The problem with diets

Nutrition Abnormal (not a lifestyle change) Loss of muscle mass

E.g. -A person who diets and loses 10 lbs. loses both fat and muscle tissue.

-When these 10 lbs are regained they are in the form of just fat tissue.

-The person now has more fat tissue than before the diet even though their weight is the same as at the outset.

GENERAL PRINCIPLES OF WEIGHT CONTROL

All weight loss is the result of a loss in muscle and fat tissue.

To offset this loss of muscle mass exercise must accommodate any weight loss program.

An increase in exercise does two things to aid in weight loss: It increases caloric expenditure. It increases metabolism by increasing muscle

massi.e. A larger engine burns more fuel.

A recommended program would be:

Decreasing intake by 200 kcal/day Increasing activity by 300 kcal/day 500 kcal/day = 3,500 = 1 lb/wk. Any successful weight loss program must

be a lifestyle change not a fad. Exercise must accommodate diet in order

to offset muscle loss and increase metabolism.