Wednesday, November 25, 2009

Vitamin D Deficiency May Increase Risk of Colds and Flu

Wondering how you can avoid this winter’s cold or flu?

You might want to try a vitamin D supplement. A new study found that vitamin D may be an important way to boost your immune system.

In the largest and most nationally representative study of the association between vitamin D and upper respiratory infections, people with the lowest blood vitamin D levels reported having significantly more recent colds or cases of the flu. The report, from investigators from the Massachusetts General Hospital, Children’s Hospital Boston and the University of Colorado Denver (UC Denver), appears in the February 23 Archives of Internal Medicine. Vitamin D is often called the "sunshine vitamin" because the human body makes it only when skin is exposed to UVB rays, a specific type of sunlight. During the summer months, it only takes 10 to 15 minutes a day to make an adequate amount. Vitamin D, which helps the bones better absorb calcium, is also included in multivitamins and added to milk.

“Low levels of vitamin D have historically been associated with rickets and other bone diseases. More recently, researchers around the world have found links between low levels of vitamin D and many chronic diseases, including heart disease and cancer. Our work supports a role for vitamin D in the prevention of common respiratory infections, such as colds and the flu,” explained Dr. Carlos Camargo of the Mass General Department of Emergency Medicine and the senior author of the study. In a subsequent study, the investigators also found that more than 6 million American children, especially minority children, aren’t getting enough vitamin D.

Camargo and his team looked at national data from 2001-2006 and the results were striking. The majority of the children had low levels of the so-called sunshine vitamin. Most African-American children had low levels, followed by Hispanic children.

The Controversy over Dosage

So what is the recommended level of vitamin D? “It used to be that deficiency was defined by what caused rickets, the most extreme form of vitamin D deficiency,” said Dr. Camargo. Rickets is characterized by softening and weakening of the bones. Recognizing that the rickets cases were increasing and that the vitamin is involved in other health issues, the American Academy of Pediatrics doubled the recommended dosage from 200 international units (IU) to 400.

“I think that was a very cautious increase; most Boston children should actually be taking around 1000 (IU’s),” explained Dr. Camargo.

Testing for Deficiency

How do you know if you need to boost your vitamin D intake?

You might ask your doctor to do a simple blood test. If your test returns low, an effective way to boost body stores is by taking a specific vitamin D supplement. Another way to increase vitamin D stores is from skin exposure to the sun—and approach that concerns dermatologists given the link between sun exposure and skin cancer. If one chooses to expose the skin to short bursts of sunshine, it’s important to know that the UVB rays that create vitamin D are not present in the northern U.S. between November and March. So if you live in the north and don’t go into the fall months with high levels of the sunshine vitamin you will most likely need a vitamin D supplement during the winter months.

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