Vitamins, or vital amines, as they were once called, are chemically-unrelated carbon-containing compounds found in the diet. Though not all vitamins are amines, they are vital for life. Vitamins perform essential functions in the body. With few exceptions, they cannot be synthesized, so they must be obtained from food. Thirteen vitamins are necessary for health. Four -- A, D, E and K -- are fat-soluble, and the remainder are water-soluble. Both of these classes contain antioxidants, which protect your body from free radical damage that can lead to disease.
Fat-soluble Vitamins
The vitamins A, D, E and K are called fat-soluble vitamins. These vitamins are more readily stored in the body than water-soluble vitamins; however, gastrointestinal disorders that impair your body's absorption of nutrients are common causes of deficiencies in these vitamins. Vitamins A and E must be obtained from food. Sources of vitamin A include dark red and green vegetables. Vitamin E occurs abundantly in both plant and animal foods. In contrast, your body is able to synthesize vitamin D and vitamin K. On exposure to sunlight, your skin can produce vitamin D; bacteria in your gut are good sources of vitamin K.
Water-soluble Vitamins
Water-soluble vitamins are used to synthesize coenzymes. Coenzymes aid enzymes in cellular processes necessary for health. Enzymes drive these chemical reactions, collectively known as metabolism, and their function relies heavily on vitamin cofactors. The nine water-soluble vitamins, which include the 8 B vitamins, often called B complex, in addition to vitamin C, cannot be stored by your body. Excessive amounts are excreted in your urine. Ensuring you meet your daily intake each day helps to prevent deficiencies.
Antioxidants
The vitamins A, C and E deserve special mention. These vitamins function as antioxidants, protecting the body from oxidative stress. Oxidative stress due to free radicals occurs continually in your body. Exposure to drugs and environmental toxins can produce free radicals, which also form as a result of normal metabolism, as in exercise and digestion. Assuring your diet contains adequate doses of these vitamins helps protect your body from chronic diseases such as cancer and heart disease.
Considerations
A balanced diet is able to provide the recommended intake of most of the 13 essential vitamins. However, due to environmental factors and the effects of aging, some deficiencies may occur. Vitamin D occurs naturally in animal foods only, and those who avoid animal products may fail to satisfy requirements for this vitamin, especially in the absence of adequate exposure to sunlight, notes Joel Fuhrman, M.D., author of "Eat for Health." Also, your body's ability to absorb B-12 decreases after age 50, and the elderly may face a deficiency even with adequate dietary intakes. In these cases, supplementation may be warranted.
References
- "Eat for Health"; Joel Fuhrman, M.D.; 2008
- Linus Pauling Institute, Oregon State University: Micronutrient Information Center: Vitamin B12
- "Pathologic Basis of Disease"; Vinay Kumar; 2005
- "Biochemistry"; Pamela C. Champe; 2005
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