Vitamins are organic compounds that your body needs in small amounts. When you do not get enough of certain vitamins, a deficiency can lead to health problems like osteoporosis or a weakened immune system. But supplementing with megadoses of vitamins can also be harmful to health, and may even cause vitamin toxicity.
Role of Vitamins
Vitamins are considered micronutrients because you only need them in small amounts. In your body, vitamins perform thousands of vital functions. Vitamin D plays a key role in calcium absorption to build strong teeth and bones. B-vitamins are important for brain and nerve health, and they support fetal development, as well. Vitamin A is essential to vision. In essence, vitamins support hormone production, growth and development, cellular metabolism and immune response. Your body cannot make vitamins, so they must be obtained from dietary or supplemental sources. Vitamins are sub-categorized into two classes, fat-soluble and water-soluble.
Water-Soluble Vitamins
Water-soluble vitamins include all the B-vitamins and vitamin C. Because unnecessary amounts of water-soluble vitamins are efficiently excreted by the kidneys each day through urine, they must be replenished on a daily basis. Water-soluble vitamins are found in whole natural fruits and vegetables, red meat and whole grains. According to nutrition specialists at Colorado State University Extension, the potency of water-soluble vitamins in fruits and vegetables can be destroyed or dramatically diminished during processing, storage and cooking. Sports coach Brian Mac asserts that, even when consumed in excess, water-soluble vitamins will not cause toxic side effects because they disperse in body fluids and are voided in the urine.
Fat-Soluble Vitamins
The fat-soluble vitamins A, D, E and K are not lost during cooking, and are stored in your liver to be drawn upon when needed. Because excess amounts are stored, megadoses of fat-soluble vitamins can become toxic. The National Institutes of Health's Office of Dietary Supplements lists toxic effects of vitamin A to include birth defects, liver problems, reduced bone mineral density, and central nervous system disorders. Too much vitamin D can cause elevated levels of calcium in the blood that can harm bones and cause kidney damage. Vitamins E and K do not generally cause toxicity, but may interfere with or exacerbate the effects of some drugs.
Vitamins and Nutrition
For people who routinely consume a healthy, well-balanced diet of whole fresh fruits, vegetables, grains and protein, vitamin deficiencies are rare. Toxicity is unlikely to occur if all or most of your vitamins come directly from natural food sources. However, people on restricted diets, those with digestive disorders that affect the absorption of fat, and patients taking lipid-lowering drugs may become vitamin-deficient. Consult your health care provider to assess whether you need a vitamin supplement.
References
- Medicinal Food News; Toxicity of Vitamins; E. Farnworth, PhD, April 2000
- National Institutes of Health; Office of Dietary Supplements; Vitamin A and Carotenoids
- Colorado State University Extension: Fat-Soluble Vitamins; J. Anderson and L. Young, August 2008
- Brian Mac Sports Coach; Vitamins
- PubMed Health; Hypervitaminosis D; Vitamin D Toxicity
- Colorado State University Extension; Water-Soluble Vitamins; J. Anderson and L. Young, August 2008
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