Vitamin D is another one of those panaceas that’s supposedly good for everything - from helping to build strong bones to protecting us against heart disease, diabetes and depression, to reducing our risk of cancer. You’ve maybe even read that you need to be taking higher amounts of this vitamin, like 10,000 IU/day, to receive its benefits. This week, however, new research from the University of Copenhagen suggests that too high a level of the essential vitamin is not so good either.  So what should the average consumer do?

Vitamin D… or shall we say “hormone D”?

This little micro-nutrient eluded scientists for a long time because it was originally identified as an essential dietary vitamin, which is a substance that cannot be produced by the body and has to be obtained from food. Unlike essential dietary vitamins, such as vitamins A, B, and C, which humans must get directly from food, vitamin D can be produced in the body of all mammals through a photosynthetic reaction when the skin is exposed to sunlight (specifically UV-B rays). The resulting substance is only a precursor to vitamin D, though, and still must undergo two transformations in the liver and kidneys in order to become useful to the body. The result is an active form of vitamin D, which is actually a hormone, just like the popular hormones testosterone and estrogen, and the stress regulator cortisol.

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Why is vitamin D important to the human body?

Vitamin D has many roles in the body. It promotes calcium absorption in the gut and it’s also needed for bone growth. Without sufficient vitamin D, bones may become brittle, thin, or even misshapen. In the 1920s, scientists discovered that vitamin D prevented rickets in children, and together with calcium, it helps protect adults from osteoporosis.

In the 1970s, scientists began to investigate vitamin D beyond its role in bone health and they discovered the vitamin D hormone in the nucleus of cells that were not part of the classical calcium maintenance system--including in the brain, lymphocytes (infection fighting white blood cells), skin, and malignant tissues. Later, in the 1980s and ‘90s, researchers also began to see its effects on the immune system, prompting further research and use of vitamin D in controlling auto-immune diseases, specifically in the treatment of psoriasis.

What should my vitamin D level be?

A committee of the Institute of Medicine said that you may be at risk of vitamin D deficiency at serum concentrations of 12-20 ng/mL, and practically all people are sufficient at levels of 20 ng/mL. Many in the medical profession, however,  disagree and put a normal level at more than 30 ng/ml. Be careful, though, because you don’t want vitamin D toxicity, which the Institute of Medicine says may occur when concentrations are above 50 ng/mL.

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