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Why You Might Want to Start Taking Vitamin D Before Winter Comes Around

Here's how vitamin D can benefit your health and how much you really need.

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The latest news on vitamin D

In recent years, D has emerged as a wonder vitamin. (Learn all the myths and truths about vitamin D.) While it had long been known to help us absorb calcium, vitamin D has been shown over the past decade or so to lower death rates from breast, colon and prostate cancer; and help ward off depression. Best Health has been keeping up on new findings, and there’s more good news:

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1. Protection for the immune system

More and more research points to vitamin D as an effective way to protect the immune system. A study in the Journal of Leukocyte Biology from May 2012 found that insufficient levels of vitamin D are related to a deficiency in the body’s immune responses. It’s possible that an increased intake of vitamin D could strengthen the body’s immune response against viral infections. The study’s authors say this may explain why cold and flu rates are higher in fall and winter, since D levels decrease at that time of year. (See the five supplements every woman should talk to her doctor about.)

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2. Reduce the risk of respiratory infection

A study published in the September 2012 issue of Pediatrics supports the possibility a daily vitamin D supplement (along with these supplements) may reduce the risk of respiratory infections in winter. For the study, 247 Mongolian schoolchildren (who are known to be at high risk for vitamin D deficiency, especially in winter) were given supplements of 300 IU daily. Risk of acute respiratory infections was halved.

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3. Faster recovery from illness

Research published in the September 2012 issue of the journal Proceedings of the National Academy of Sciences suggests that vitamin D supplementation could improve recovery rates for patients with an infectious disease such as tuberculosis. “Patients who had vitamin D on top of antibiotics cleared the TB bacteria from their lungs 13 days more quickly than those who just had standard treatment alone,” lead researcher Adrian Martineau told Best Health. The results suggest vitamin D helps dampen the body’s inflammatory response to infection and could even, Martineau speculates, enhance recovery from pneumonia. (See the foods that fight the flu and boost immunity.)

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The bad news

But the latest research has not all been positive. A study at the University of Otago in New Zealand showed vitamin D supplementation in healthy adults who do not have a vitamin D deficiency may not reduce the incidence or severity of colds. The 322 healthy adults in this study were randomly assigned to receive either a monthly dose of 100,000 IU of vitamin D3 or a placebo. At the end of the 18-month study, researchers found no significant difference between the two groups.

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How much do you need?

Health Canada’s current dietary recommendations for vitamin D:
Infants up to 1 year = 400 IU (10 mcg) per day
Children and adults age 1 to 70 = 600 IU (15 mcg) per day
Pregnant or breastfeeding women = 600 IU (15 mcg) per day
Adults over age 70 = 800 IU (20 mcg) per day

Osteoporosis Canada has higher recommendations; they are:
Adults age 19-50 (including pregnant or breastfeeding women)  = 400-1,000 IU per day
Adults over age 50 = 800-2,000 IU per day (Note: Taking more than 2,000 IU daily should be done under medical supervision)

This story was originally published in January 2010.

Next, learn why you should talk to your doctor before taking supplements.