Vitamin A and your bones

Mae West once said, "Too much of a good thing is ...wonderful." Whatever else she had in mind, it certainly wasn't vitamin A. Although doctors have long known that very large amounts of vitamin A are toxic, studies show that modest doses previously considered safe can increase your risk of fracture.

What is vitamin A?

Like all vitamins, vitamin A is an organic (carbon-containing) compound that is required to keep the body's metabolism running smoothly. Because the body cannot manufacture vitamins, all 13 must be consumed on a regular basis. Only tiny amounts are required to prevent vitamin-deficiency diseases, but slightly larger amounts of some, such as the B vitamin folic acid, may have additional benefits. But although vitamins are necessary and all-natural, excessive amounts can be harmful.

Along with vitamins D, E, and K, vitamin A is a fat-soluble vitamin. That means it is absorbed into the body with dietary fat, and then stored in the body's own adipose tissue. As a result, you can store enough vitamin A to last for months, but if you take in more than you need, it will slowly build up in your body's tissues. In contrast, the water-soluble vitamins (the B vitamins and vitamin C) are not stored in the body to any appreciable degree; extra amounts are passed into the urine, so toxic reactions occur only if very large amounts are ingested (but deficiencies develop relatively quickly if consumption lags behind need).

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