Vitamins in mega doses can cause harm.
With 85 percent of Americans taking some form of supplement some time during the year and a greater prevalence of fortified foods, the potential for vitamin toxicity increases. Excess dietary ingestion, whether by a single large dose or chronic elevated doses, can cause toxic reactions in the body.
Types
Vitamins generally are classified according to their solubility. The four fat-soluble vitamins--A, D, E and K--are more likely to cause toxicity than the water-soluble vitamins, such as vitamin C and the B-complex group. Humans store fat-soluble vitamins in body tissues, while they excrete water-soluble vitamins in the urine without storing them for long-term.
Function
Vitamins act as enzymes or coenzymes for essential metabolic reactions in the body. Humans can synthesize some vitamins from precursors but generally must consume vitamins partially or wholly through their diet.
Significance
Vitamin A toxicity can result in birth defects, osteoporosis and disorders of the liver and central nervous system. Acute symptoms include nausea and vomiting, dizziness, blurred vision and impaired muscular coordination.
Vitamin D toxicity causes hypercalcemia and manifests similar symptoms of nausea, vomiting and unsteadiness as well as anorexia, frequent urination, excess thirst and fatigue. Toxicity may lead to impaired kidney function and organ calcification.
Considerations
Eating a variety of healthy foods, rich in fruits and vegetables, proves the safest, most natural way to consume vitamins without worry of toxicity.
Warning
Mega doses of vitamins via supplements most likely causes toxicity. Because the federal government does regulate or analyze vitamin supplements, the strength of the various products can vary. According to ConsumerLab.com, an independent testing agency, three out of four children's multivitamins contained excess vitamin A.
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