General Nutrition: FAQ

Protein and Amino Acids
Vitamins and Minerals
Protein and Amino Acids

What is protein?

Protein is one of the most essential nutrients in our body. It has a wide range of physiological functions that are required for achieving optimal physical performance. Protein forms the structural basis of muscle tissue, is a major source of energy for muscle contraction and is also the major component of enzymes in the muscle.

What is the structure of protein?

Protein is a complex chemical structure containing carbon, hydrogen and oxygen similar to carbohydrates and fat. Protein also has nitrogen. These elements are combined and are formed into amino acids, each possessing an amino group (NH2) and acid group (COOH), and the reminder being different combinations of carbon, hydrogen, oxygen and sometimes sulfur. There are 20 amino acid (peptides), all of which can be combined together in different ways to form proteins that are needed for the structure and functions of the human body (Williams, 1893).

What are some of the issues related to protein supplements?

1. Athletes may use protein supplements to enhance endurance and increase or maintain muscle mass to improve strength and size.
2. A high-protein diet doesn't build muscle and burn fat as some people think.
3. Regular physical activity and dietary protein builds muscle strength.
4. Athletes may need slightly higher levels of protein, derived from protein-rich foods such as meat, poultry, fish, eggs, and dairy products.
5. Depending on the protein sources chosen, a high protein diet may also be high in fat and calories.
6. Diets very high in protein can put a strain on the liver and kidneys.
(From The American Dietetic Association's Complete Food & Nutrition Guide, 1998)

What are protein requirements?

1. The RDA for protein is 0.8 grams/kg/day.
2. Adequate energy intake primarily from carbohydrates will insure protein balance.
3. Urea, a by-product of protein metabolism, increases in the urine during exercise.
4. Estimates of increased protein requirements for endurance athletes vary, with recommended protein intakes of 0.97 to 1.39 g/kg/day.
5. Most experts agree that additional protein can be easily obtained through a balanced diet.
6. Protein need can be calculated as a percentage of total energy and on a per kilogram body weight basis (American Dietetic Association, 1997).

What are the possible adverse effects of using protein supplements?

1. High protein diets are discouraged by most nutrition experts due to increased stress placed on the kidneys.
2. The high nitrogen load excreted as urea can cause fluid imbalance leading to dehydration.
3. Diets high in animal sources of protein are often associated with high fat intake and increased risk of heart disease.
4. Large ingestion of some amino acids can interfere with the absorption of other amino acids leading to metabolic imbalances.
5. Mild to severe stomach cramping and diarrhea, dehydration, and gout have been associated with use of certain amino acid supplements.

What are common sources of protein and amino acid products?

1. The protein content of powdered or liquid protein formulas is derived form natural food sources such as milk, egg, or soy protein.
2. Amino acids marketed as ergogenic aids include the branched chain amino acids (BCAA) leucine, isoleucine, and valine. During exercise the liver releases BCAA which are delivered to the muscle. Degradation of muscle protein which also occurs during exercise leads to the production of BCAA within the muscle.
3. Leucine is the only amino acid that can be oxidized for energy and is important in muscle metabolism because it can provide energy to muscle during starvation. Leucine also has a stimulatory effect on the secretion of insulin.
4. Over secretion of insulin can result in a decrease blood sugar and reduced athletic performance.

What are the effects/actions of l-carnitine?

Carnitine (L-3 hydroxytrimethylammoniobutanoate) has several roles on the mammalian cellular metabolism. L-carnitine is believed to increase long chain fatty acid oxidation in skeletal muscle during exercise. Dietary sources of carnitine are meat and diary products. Advocates of L-carnitine supplementation claim that it increases aerobic and anaerobic capacity and promotes fat loss. The most commonly cited dosage of oral carnitine is 2-6 g/day consumed in two to three doses with meals. L-carnitine supplementation may have beneficial properties, however, there is a lack of information regarding its long term use (Tonda and Hart, 1992).

What are the adverse effects of using l-carnitine supplements?

Nausea, vomiting, abdominal cramps, diarrhea

Does carbohydrate supplementation during exercise improve performance?

Research has shown that carbohydrate supplementation during exercise can improve long-term endurance performance (for activities lasting 90 minutes or more) and delay fatigue 30 to 60 minutes. The most recent guidelines on carbohydrate supplementation during exercise are the following recommendations:
1. Consume 200-400 ml of a moderately concentrated 5-7% carbohydrate drink.
2. Continue consuming 100-150 ml of the same drink at 10-15 min intervals for the first two hours of exercise.
3. After two hours switch to a more concentrated drink (15-20% carbohydrate).
4. Choose a drink that is palatable.
5. One alternative to purchasing sports drinks is to dilute any fruit juice 1:1 with water and add a teaspoon of salt per liter. This should approximate carbohydrate, electrolyte and osmolality values of commercial sports drinks (Wolinsky, 1997).

Information from NCAA,

Vitamins and Minerals

What are vitamins and minerals and how do they work?

Vitamins and mineral are complex organic compounds that have an important function in the metabolism of protein, carbohydrates, and lipids, and in muscle function (ADA, 1999). Vitamins and minerals are essential for many different physiological processes in the body. These nutrients contribute to the process of energy metabolism, nerve function, immune function. Physical activity increases the need for some vitamins and minerals. Ideally, such requirements should be met by maintaining a balanced, high carbohydrate diet with moderate protein and low fat. All student athletes should carefully monitor their energy levels, be aware of the amount of rest they regularly get, and assess their relative degree of freedom from injury and sickness, before assuming that their nutritional status is adequate.

What are vitamin and mineral requirements?

Recommended Daily Allowances (RDAs) of vitamins and minerals are not identical for everyone. Vitamin and mineral intakes below the RDA do not always indicate vitamin and mineral deficiency; however, vitamin and mineral intakes below the RDA can increase the risk of developing a deficiency state. Most athletes consume a high calorie, balanced diet that contains the RDA of all nutrients and as a result should have few vitamin or mineral deficiencies (USDA, 1999). Other studies have shown vitamin and mineral imbalances among athletes based on biochemical blood analysis (Armstrong and Maresh, 1996; Beltz and Doering, 1993). These athletes include those who are on weight loss diets, have restricted the variety of food in their diets, have limited access to food, or have eating disorders.

What are the effects/actions of vitamin and mineral supplements?

Some student athletes have used vitamin and mineral supplements to increase strength or muscle mass, enhance anaerobic and aerobic capacity, increase mental well-being, accelerate post-exercise recovery, reduce body fat, decrease pain or inflammation, or neutralize free radicals and prevent oxidative damage. Female student athletes may use iron supplements because of iron loss during menstrual cycles. Some female athletes with low estrogen levels have used calcium supplements when amenorrheic after strenuous workouts.

What are the possible adverse effects of using vitamin and mineral supplements?

Excessive consumption of vitamin C, niacin, vitamin B6, folic acid, and vitamin B12 may lead to liver damage, nausea, inflammation of the oral cavity, dermatitis, muscle weakness, and fatigue. Excessive use of iron may lead to inhibition of electrolyte and trace elements absorption. Zinc supplements exceeding the RDA may lower HDL levels and lower copper and iron levels in the blood (ADA, 1999).

What are the sources of vitamins and minerals?

Vitamins are classified as either water soluble (C and B vitamins) or fat soluble (A, D, E, K). Water soluble vitamins are not stored in the body and must be supplied in the diet regularly. Fat soluble vitamins are primarily stored in the liver and can accumulate to toxic levels. Minerals are essential components of cell membranes, enzymes, and glandular secretions and their function is to regulate osmotic pressure, acid-base balance, blood volume, and the activity of nerves and muscles. Minerals include chloride, sodium, potassium, calcium, and magnesium. The heart muscle is sensitive to imbalances in these substances, and in cases of severe depletion the heart may develop irregularities (USDA, 1999).

Information from NCAA,


What is the definition of herbs?

Herbs are defined as plants or plant extracts which are used for their non-caloric benefits. The use of herbs to enhance physical performance is very common among athletes.

GINSENG (American, Chinese, Korean, Siberian)

What are the actions/effects of ginseng?

Reports of the effects of ginseng include claims for increased endurance, increased muscle strength, improved recovery from exercise, improved oxygen metabolism during exercise, improved auditory and visual reaction time, improved mental concentration, and improved visual/motor coordination, and mental accuracy.

What are the adverse effects associated with using ginseng?

Individuals who use ginseng may experience nervousness, insomnia, high blood pressure, GI discomfort, headaches, skin eruptions, chest discomfort, depression, and spontaneous vaginal bleeding.

Information from NCAA,


What are the effects/actions of creatine?

Creatine, or methylguanidine-acetic acid, is a naturally occurring compound. In healthy individuals the total amount in the body is about 120g. Ninety five percent of creatine is found in the skeletal muscle. Sixty percent of creatine is in the form of phosphocreatine (PCr), which is considered to facilitate increased anaerobic energy (Wolinsky, 1997). The role of creatine in muscle energy metabolism and fatigue is to maintain adenosine triphosphate (ATP) availability, modulate metabolism, and buffer hydrogen ion accumulation during contraction (Greenhaff, 1996). In effect, this means that the student athlete would have more muscle energy and therefore be able to do more intense anaerobic workouts. Development of fatigue during short-duration exercises has been associated with the depletion of muscle PCr stores (Hultman et al., 1991).

What are the adverse effects of using creatine supplements?

Reports related to creatine supplementation have indicated that one third of individuals trying creatine supplements are unable to absorb the extra amounts into their muscles and experience no improvement in muscle mass or athletic performance (Tarlach, 1998). Endurance athletes (marathoners) may find creatine supplementation counterproductive since the extra muscle mass creatine builds slows them down (Tarlach, 1998). Increased cramping and muscle strains may be associated with intracellular swelling (Williams and Branch, 1998). Endurance athletes may find creatine usage counterproductive since the increase mass and increase in weight may contribute to lowered endurance (Volek, 1997; Hultman, 1991). Recent studies reported that a 25 year old soccer player developed renal dysfunction while taking creatine. He had not exceeded recommended doses. His renal function returned to normal after he stopped taking creatine (Poortmans, Aucquier, and Renaut, 1997; Pritchard and Kalra, 1998).

Information from NCAA,


What are the properties of chromium?

Chromium is an essential trace mineral in the body that aids insulin in the transfer of glucose from the bloodstream into the cells. Two basic claims that are made by the manufacturers of this product are weight loss and increase in lean body mass. However, chromium supplements produce results only for individuals who are chromium deficient. Acute aerobic exercise increases chromium losses (Anderson et al. 1982, 1984, and 1988).

What are the adverse effects of using chromium supplements?

Doses of over 200 mcg may lead to anemia.

What are the natural sources of chromium?

Natural sources of chromium are whole grains, fruits, and vegetables. If enough chromium is obtained from a balanced diet no additional benefits are obtained from chromium supplements.

Niacin (B3: Nicotinic Acid)

What are the actions/effects of niacin?

Nicotinic acid (Niacin) in large doses reduces serum lipids. It also produces histamine leading to vasodilatation and increased blood flow (ADA, 1999). Nicotinamide (Niacinamide), does not have hypolipodemic or vasodilating effects. Nicotinamide is used by the body as a source of niacin. The different biochemical processes involved in lipid metabolism, tissue respiration, and glycogenolysis all require nicotinamide.

What are the sources of niacin?

Niacin (Vitamin B3) is the common name for nicotinic acid. Nicotinic acid functions in the body as a component of two coenzymes: NAD (nicotinamide adenine dinucleotide, coenzyme I) and NADP (nicotinamide adenine dinucleotide phosphate, coenzyme II), which serve a role in oxidation-reduction reactions essential for tissue respiration. Nicotinic acid is present in NAD and NADP in its active form of nicotinamide.

What are the adverse effects assiciated with using niacin?

Individuals who use large amounts of niacin may experience a flushing of the skin, gastro-intestinal distress, abdominal pain, diarrhea, nausea, and vomiting.