Vitamins and Minerals
Vitamin and mineral deficiency diseases, even in industrialized nations, such as the United States, were relatively common prior to World War II. Today, with the fortification of the food supply and the widespread use of multivitamins, classical vitamin deficiency diseases, such as scurvy and rickets, are rare except in the case of:
- Specific disease states.
- Drug effects on vitamins.
- Extreme malnutrition due to poverty.
On a global basis, vitamin deficiencies still occur in many large countries, such as India and China, in both rural and urban populations. What can be classified as suboptimal intake of some vitamins, such as vitamin D in areas of low-sun exposure, is a more recently discovered and important area of vitamin deficiency, where supplementation is being recommended by authorities in the field.
Establishing RDA Levels
The recommended dietary allowance (RDA) is normally issued every 10 years by the National Academy of Sciences Food and Nutrition Board to help guide healthy individuals and to help in planning various national nutrition programs for infant feeding and school nutrition. The RDA levels are normally set above the threshold needed to prevent deficiency diseases, but in some cases the levels are below those some experts would like to see for the prevention of disease. In fact, in 1980, the guidelines were not issued due to a philosophical difference of opinion among the expert members of the group as to whether the RDA should be raised to encourage intake of Vitamin A-rich (carotenoid) and Vitamin C-rich foods, such as fruits and vegetables. The controversy was finally settled with the issuance of the 1989 guidelines that reverted to the original aim of averting nutritional deficiency states through public policy recommendations.
Fat-Soluble Vitamin Deficiencies
The fat-soluble Vitamins A, D, E and K have separate functions. Vitamins A and D are closely related to steroid hormones and act to induce the synthesis of specific proteins and to maintain normal cellular function. Rare deficiencies of Vitamin A cause night blindness and susceptibility to mumps infection. Deficiencies of Vitamin D cause a bony disease called rickets, and suboptimal intakes of Vitamin D have been related to various forms of cancer. Vitamin E includes a family of eight compounds found in plant cell walls where they act as antioxidants. Vitamin E deficiency does not occur in humans, but this family has interesting functions in the body beyond antioxidation. Vitamin K is a fat-soluble vitamin. The “K” is derived from the German word “koagulation.” Coagulation refers to blood clotting, because Vitamin K is essential for the functioning of several proteins involved in blood clotting.
Unlike fat-soluble vitamins, which can be stored after a single administration for long periods of time, water-soluble vitamins need to be supplied in foods and supplements on a regular basis to avoid deficiency. Industrialized societies have few cases of water-soluble vitamin deficiency, except in homeless or alcoholic individuals. The recent increase in obesity surgeries, which lead to malabsorption of Vitamin B12 by bypassing the stomach, have led to a new group of individuals at risk of vitamin deficiencies. Strict vegans, individuals with food intolerances, and raw food enthusiasts can also develop vitamin deficiencies if their choices of foods are narrowed significantly.
Recent studies in mice have indicated an interrelation between energy balance, diet, and the composition of the gut bacteria.
The Fitness Textbook will teach you the basic principles of human performance nutrition, including muscle metabolism and fuel utilization before, during and after exercise.