Vitamin D Is Essential to the Modern Indoor Lifestyle

By Seppa, Nathan | Science News, October 23, 2010 | Go to article overview

Vitamin D Is Essential to the Modern Indoor Lifestyle


Seppa, Nathan, Science News


It's known that vitamin D is necessary for proper bone formation and maintenance. But recent decades have seen a torrent of studies suggesting that vitamin D can also affect many other aspects of health; some scientists have come to consider the daily recommended intake of 400 international units of vitamin D far too low. Michael Holick is a biochemist and endocrinologist at Boston University who has spent a career researching the effects of vitamin D (which is actually not a vitamin but a hormone precursor). His new book is The Vitamin D Solution (Hudson Street Press, 2010). Holick recently spoke with Science News biomedicine writer Nathan Seppa.

How much vitamin D do we need?

Children should be taking at least 400 to 1,000 international units of vitamin D as a supplement every day, and adults should take 1,500 to 2,000 IU.

What about pregnant or breast-feeding women?

We tested pregnant women who were taking a prenatal vitamin containing 400 IU of vitamin D each day and drinking two glasses of fortified milk, and found that 76 percent of them--and 81 percent of their newborns--were still vitamin D deficient at the time of giving birth. We also estimate that most breast-feeding women are vitamin D deficient, and they pass along deficient milk to their infants.

Vitamin D deficiency has been linked to increased risks of infectious diseases, cancer, autoimmune diseases, heart disease, cognitive decline, Parkinson's disease, asthma, mood disorders and even diabetes. Is there biological evidence to show how vitamin D could influence so many conditions?

Sure. For example, we know that immune cells called macrophages activate vitamin D, which causes cells to make defensin proteins that specifically kill infective agents like tuberculosis bacteria. A Japanese study recently found that children receiving 1,200 IU of vitamin D each day reduced their risk of getting the flu by almost 50 percent. Every tissue and every cell in the body has a vitamin D receptor protein. It's estimated that upwards of 2,000 genes are directly or indirectly regulated by vitamin D.

[ILLUSTRATION OMITTED]

Have there been clinical trials showing the utility of vitamin D?

Absolutely. For instance, a trial of postmenopausal women showed that taking vitamin D over four years reduced their risk of cancer by 60 percent. …

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