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A well balanced diet, containing essential vitamins and nutrients, is required to maintain health. The effect of diet on the immune system regulates the production of antibodies necessary to ward of disease. The recommended daily allowance (RDA) for food combining, provided by the Food and Nutrition Board of the National Research Council/National Academy of Science, may be used as a guide when designing diet. Combinations of carbohydrates, fats and proteins provide all of the daily nutritional requirements for an adult performing moderate amounts of exercise. Approximately 50% of the diet is accountable to carbohydrates. Endurance athletes may require greater percentages, this can be used as a general figure. The recommended allowance for fat is approximately 30% of the diet. The majority of these calories should be unsaturated fat, either monounsaturated or polyunsaturated, as opposed to saturated fat that when consumed in large doses is detrimental to health. The RDA for protein in adults is calculated as 0.83 grams per kilogram body weight. This accounts for approximately 12-15% of total dietary intake.(Book, 6) Variations may occur if individuals indulge in unusually athletic or sedentary lifestyles. A multitude of foods within each of these groups is essential to ensure well rounded health.
Studies have shown that vitamins and nutrients are required for proper functioning of the immune system. Included in this category are vitamins A, B, C, and E along with the minerals iron and zinc and the trace elements selenium and copper.(Book, 7) Following is a brief description of each vitamin, mineral, and trace element along with the RDA’s, and natural sources where the substance can be found.
Vitamin A, a fat soluble vitamin, is stored in the adipose cells of the body. It is necessary for maintenance of the mucousal lining of the lungs and other organs. These linings provide a first line of defense for the immune system. The RDA for this vitamin is 800-1000 RE (retinal equivalents). It is prevalent in liver and egg yoke. Dairy products can also be fortified with vitamin A.
Vitamins B-6 and B-12 are both water soluble vitamins. They play a role in the formation of red blood cells and metabolism, but only B-6 is responsible for synthesizing antibodies. The RDA for these vitamins are 1.6-2.0 mg and 2 mcg respectively. They can be obtained through the consumption of animal products and also from whole grains, legumes, potatoes, and bananas.(Book, 2)
Vitamin C, a water soluble vitamin, is known to enhance cellular immunity. Lymphocytes and macrophages become more efficient in the presence of vitamin C. These leukocytes are responsible for recognizing and destroying antigens. Under this principle, there is less opportunity for virus or infection to enter the system. Vitamin C also aids in the healing process, iron absorption, and in the prevention of oxidation. The RDA for vitamin C is 60 mg. Some sources are citrus fruits, papaya, tomatoes, and green vegetables.(Book, 3)
Vitamin E, a fat soluble vitamin, works as an antioxidant and increases the production of leukocytes. The RDA is 8-10 mg. This vitamin can be found in whole grains, vegetable oil, nuts, legumes, green leafy vegetables, and eggs.
Iron, a necessary component of red blood cells, is part of hemoglobin and myoglobin which distribute oxygen throughout the circulatory and muscular systems. Iron is the most prevalent mineral in the body and has the ability to strengthen the immune system, thereby providing a greater resistance to infection. However, if illness is already present, iron may promote the growth of detrimental bacteria. An iron deficiency in the body results in reduced levels of oxygen being transported through the system. This condition is referred to as anemia and may be treated with iron supplementation. The RDA is 10-15 mg. Its most prevalent sources are red meat and dark green leafy vegetables.(URL, 7)
Zinc plays a critical role in the formation of immune cells and the healing process. It is also involved in digestion, reproduction, and kidney function. Zinc aids in the proper functioning and activity of over 200 enzymes throughout the body. The RDA for zinc is 15 mg for men and 12 mg for women. Women who are pregnant or lactating require additional dosages, often times up to 19 mg. This mineral is abundant in oysters and seafood products. Other sources of zinc are meats, shellfish, dairy products, and legumes.
Selenium is a vital antioxidant, especially when complimented by vitamin E. This trace mineral prevents the formation of free radicals, is essential for pancreatic function, tissue elasticity, and stimulation of the immune system. Selenium aids in protecting the body against lung and rectal cancer. The RDA is 55-70 mcg. Fruits and vegetables are often rich in this substance, however, selenium deficient soil is present in areas where land is over used or unusually stressed. Chemical fertilizers also prevent the regeneration of soil. Selenium can be found in shellfish, eggs, garlic, and liver.(URL, 6)
Copper aids in the structural modifications which take place when iron is processed into hemoglobin. Basically, it aids in the formation of red blood cells. Copper is also necessary for the proper maintenance of bones, blood vessels, and nerves. The RDA for copper is 1.5-3.0 mcg. Copper can be found in whole grains, organ meats, shellfish, legumes, liver, nuts, and seeds.(URL, 10)
These substances should not be taken indiscriminately. Consumed in excess, some of the essential nutrients may cause damage to an otherwise healthy organism. For example, excess dosages of iron can attack many systems within the body. It is important to become familiar with the substances before ingesting them. Knowledge can prevent physiological mishaps.
Do differences in diet effect exercise performance? If the proper combinations of carbohydrates, fats, and proteins are maintained, performance should remain consistent regardless of choice of intake. Essentially, an athlete can consume meat products and demonstrate equal performance as an athlete with a lacto-ovo vegetarian tendency. As long as recommended daily allowances are observed, differences should be undetectable.(Journal, 3)
In closing, the major element to maintaining a healthy immune system lies in proper nourishment and a well rounded diet. A variety of foods may be all that is necessary to keep the immune system functioning at an optimal level.