PED 291 - Chapter 2 Notes

Macronutrients and Food Energy

Macronutrients: Carbohydrates, fat (lipids), and proteins

Monosaccharide - the basic unit of carbohydrates (CH2O).

Glucose- forms as a natural sugar in food OR: is produced in the body by the hydrolysis (digestion) of complex carbohydrates.

After absorption by the small intestine, glucose can be:

a. used by the cells for energy
b. stored as glycogen in the muscles and liver
c. converted to fats for energy storage

Other sugars (fructose-fruits and honey, and galactose, which forms milk sugar….lactose, is converted to glucose for energy metabolism.

Disaccharide-2 monosaccharide (double sugar)

There are 3 significant types:

a. sucrose-glucose + fructose (brown sugar, honey)
b. lactose-glucose + galactose (milk)
c. maltose-glucose + glucose (beer, cereal)

Polysaccharides

1. plant-

a. starch-complex carbos. There are hundreds of sugar molecules linked together (bread, peas, beans).
b. Fiber-non digestible. They hold water and give bulk to food residue in the intestines, increasing stool wt by 40-100%. The water soluble fiber (oats, brown rice, peas, carrots, apples) aid in lowering cholesterol.

Fiber slows carbohydrate digestion so the intestines absorb it more slowly. We need 20-35 grams of fiber per day, but the average American eats 12-15.

During the process of glucogenesis, many molecules form glycogen, the storage polysaccharide in muscle and liver.

An 80 KG person stores about 500 grams of CHO, 400 are muscle glycogen (the major sources of energy) and 100 or so is liver glycogen. CHO are 4 calories of energy per gram, so the 2000 or so kcals stored can enable a person to run about 20 miles.

Glycogenolysis is where liver glucogen reconverts to glucose and is transferred in the blood to the working muscles.

When someone starves him or herself or has worked out very hard, glucose is produced through protein's amino acids (gluconeogenesis).

If there is more than 500 g of glycogen stored, the pancreas secretes insulin so the muscles will increase the use of glucose. If the glucose level is low, insulin's opposing hormone (glucagons), normalize blood sugar levels by stimulating liver glycogenolysis and gluconeogenesis. Glucagon is the insulin antagonist.

So: eat at regular intervals every day, and eat a lot of small meals.

A. Energy source

For people who work out, carbohydrate intake maintains the body's limited glycogen stores. To many CHO will overfill the cells capacity for storage, and the excess will convert to fat, and be stored as such.

b. Protein sparer

CHO preserves tissue protein- if you don't eat, the energy your system receives will be by breaking down muscle.

C. Metabolic primer

CHO breaks down fat- eating them facilitate the body's use of fat for energy, especially during exercise.

D. Central nervous system fuel

CHO is fuel for proper functioning of the central nervous system.

If people work out hard and don't refill (hypoglycemia), or a modest blood glucose reduction occurs. The person will feel weak, hungry, and or dizzy.

Carbohydrate content of selected foods…pg. 46

A 70 KG person should have 300 g of CHO per day. Most people consume half or more from simple sugars (60 pounds of table sugar per year on average and 46 pounds of corn syrup).

60 percent of CHO should be unrefined, fiber rich grains, fruit, and vegetables.

During heavy training CHO intake should be 70 percent of the diet.

Carbohydrate utilization during exercise pg. 47.

During all out exercise, a person's energy source is primarily carbohydrates. It is the only macronutrient that produces energy anaerobically, through intermuscular glycogen.

If you have enough oxygen but no glycogen, you bonk. Why does this happen?

Lipids (fat)

Fat breaks down slower than CHO in your body because it contains more hydrogen atoms.

3 groups of fat

1. Simple- consists of triglycerides, the major storage form of fat, more than 90 percent.

2. Saturated fat- found in animal products, and dairy fats. From plants it includes coconut and palm oil, vegetable shortening, hydrogenated margarine, (cake, pie, and cookies).

3. Unsaturated- contains monounsaturated fats (canola oil, olive oil, peanut oil), and polyunsaturated fats (safflower, sunflower, soybean, and corn oil). Plant oils are unsaturated and are liquid form at room temp, but through hydrogenation they can turn solid in the body when consumed.

Individuals should consume no more than 10 percent of total energy from SATURATED FATS. Unsaturated fats have high-density lipids, which reduce cholesterol levels.

Compound Lipids

A group of compound fats contain lipoproteins-formed in the liver from the union of triglycerides, phospholipids, or cholesterol…with protein.

Lipoproteins are very important- they are the main form for lipid transport in the blood. If blood lipids did not bind to protein, they would rise to the top like the cream in milk.

Types of lipoprotein cholesterol

a. LDL- bad cholesterol- usually between 60-80 percent of total cholesterol. These damage and narrow arteries. The amount we have depends on: exercise, fat accumulation, and composition of one's diet.

b. HDL- good cholesterol- a scavenger- it removes cholesterol from the artery wall for transport to the liver. It then turns into bile and the intestine gets rid of it.

c. Derived lipids- cholesterol- from food, or our body does make up to 2 grams per day. It has positive benefits: it builds membranes, synthesizes vitamin D, and many hormones, including the sex hormones (estrogen, progesterone). It also helps body tissues form during fetal development.

Contained in organ meats, shellfish, and dairy products.

Roles of Lipids:

1. Energy reserve: it provides 80-90 percent of the body's energy requirement (1 gram=9 calories of energy). Carbohydrates can supply a runner for an hour and a half. The fat in our body can supply us for up to 120 hours of exercise. It spares protein so your body does not break down muscle when you deplete CHO stores.

2. Protection and insulation- 4 percent protects vital organs against trauma. Subcutaneous fat just below the skin insulates us so we can tolerate the cold (the polar bear).

Note: Too much fat will not allow heat to escape as efficiently.

3. vitamin carrier- fat is a carrier and transport mechanism for the fat-soluble vitamins ADEK. We must take in about 20 grams of fat per day to do this efficiently.

4. Fat actually spares protein, so your body will not break down muscle when you deplete CHO stores.

Unsaturated fatty acids should be 70 percent of lipid intake, and that we limit our cholesterol intake to 300 milligrams per day. Table 2.2 shows some common foods and it's content. Page 52 shows how to choose your fat. The body's muscle usage of fat increases after an hour of moderate exercise.

Proteins- a normal adult has about 10 kg of protein (muscle)

A protein molecule forms from its building blocks called amino acids. The functions and properties of a protein depend on the sequencing of specific amino acids. (from 2 to over 100 at any one protein)

The body requires 20 amino acids. Our body makes 12 of them (nonessential-they are important but the body makes enough to meet the demands of normal growth and repair), and 8 we get from food (essential).

You get essential from plant or animal foods. There is no health or physiological advantage from where you get them.

Complete proteins- has all the essential amino acids.(the egg is 100% protein)

Incomplete proteins-lack one or more essential aminos.

The biologic value of protein (how complete is it) foods is listed on page 54…table 2.3.

Role of protein: all protein contributes to tissue structures, none of it is stored. It is 12-15 percent of body mass, but different cells have more protein (red blood cells and muscle cells…20 percent, brain cells….10 percent).
Weight lifting increases the protein content of muscle. Protein supervises cell protein production, transmits hereditary characteristics, makes skin, hair, nails, bones, tendons, ligaments, and regulates the energy release between fats, carbos, and proteins.

Amino acids in protein allow the body to: synthesize many diverse compounds; activate vitamins that provide metabolic and physiologic regulation. Tissue synthesis (anabolism) takes up a third of protein intake during the rapid growth years.

The vegetarian's main nutritional concern: obtaining enough high quality protein. (mix and match..pg. 54)

EATING EXCESSIVE PROTEIN PROVIDES LITTLE BENEFITS TO ATHLETES, AND COULD BE HARMFUL TO THE LIVER AND KIDNEYS. This is because protein contains nitrogen, which has to be broken down. Plants sources of protein get nitrogen from soil.

Whether it's animal or vegetable sources, there is no physiological advantage to either one.

The liquids, powders, and pills represent a waste of money because these products contain predigested proteins to simple amino acids through chemical action in a lab. These aminos do not absorb quicker or more efficiently; in fact, the intestines handle protein better in a complex form.

The conversion of protein to fat or carbohydrate is called deamination. This process forms urea in the liver which the kidneys need to excrete. Thus excess fluid promotes fluid loss.

An athlete who is consuming adequate calories is probably consuming adequate levels of protein, although heavy training athletes (2-6 hours per day) could put 1.2-1.8 g of protein per kg of body weight, compared to 0.9. table 2.4

Catabolism-the breakdown of protein into amino acid components. Afterward the nitrogen breaks off (deamination) to the liver.

If all the extra protein you take would matter, think of how big we would be. It will store as muscle glycogen or store as triglycerides and fatty free acids in adipose tissue.

Muscle can be degraded in the body to supply energy. The increased release of the amino acid alanine from active muscles during exercise (it is made from glucose derived pyruvate) provides energy and then enters the liver for deamination (it is exposed of). What is left is converted to glucose and enters the blood to be delivered to the muscle. THIS IS CALLED THE ALANINE GLUCOSE CYCLE, and supplies about 15 percent of energy during long term high intensity exercise (page 59).

Label reading information Page 63-64.