For many years, doctors have recognized that ample blood levels of vitamin D are essential for lowering the risk of osteoporosis and bone fractures because this vitamin enhances calcium absorption from the intestine.

More recently, studies have suggested, but have not proved, that vitamin D deficiency increases the likelihood of colon and breast cancer. Now, 2 recent studies published in Archives of Internal Medicine provide strong evidence that vitamin D deficiency is indeed linked to a greater risk of heart attacks and premature death from cardiovascular disease and other causes.

Workers at the Harvard School of Public Health studied about 18,000 men who did not have a diagnosis of coronary heart disease at the start of the study. During the 10-year follow-up period, the researchers found that men with vitamin D deficiency were twice as likely to have a heart attack compared to those whose blood levels of vitamin D were sufficient.

In another study, Austrian researchers followed about 3,000 men and women with an average age of 62 for nearly 8 years. Those with the lowest blood levels of vitamin D had twice the risk of dying, mostly of cardiovascular disease, compared to those who had the highest levels of vitamin D. 

The issue is somewhat clouded, however, by results from the Framingham Offspring  Study. In this study, which followed 1,700 participants — a much smaller sample size than was used in the two studies above — for 5.4 years, vitamin D levels were not associated with the risk of dying. The risk of heart attack was doubled only in those with high blood pressure.

In any case, it's worthwhile to make sure your body has adequate blood levels of vitamin D, surely to prevent broken bones and probably to increase your chances of living longer by avoiding certain cancers and heart attacks.

What do I recommend?  I suggest that you ask your doctor to measure your 25-hydroxyvitamin D blood level, a test that is not done routinely by most physicians. Vitamin D deficiency is common in the U.S., as I learned this April when my 25-hydroxyvitamin D level was found to be only 11 nanograms per milliliter (ng/ml).  Experts recommend that doctors aim for values greater than 30 ng/ml in their patients, and so I was immediately placed on large doses of vitamin D.

Many of us need to take vitamin D supplements because it is almost impossible to get enough vitamin D from foods. And most people also don't take the time or have the opportunity to get the 10 minutes of daily exposure to sunlight during peak hours, which can provide ample vitamin D formation by the skin.

Vitamin D pills are available without prescription, and it is safe to take as much as 1,200 mg a day. But since excessive intake can lead to vitamin D toxicity, people who have severe vitamin D deficiency must get a prescription from their doctor for the larger doses necessary to correct their problem.