An interesting report in a recent edition of the Archives of Internal Medicine indicates that vitamin D deficiency may increase the risk of heart attack. What does this mean for you?

First, let's look at the data. The report is part of a larger study of 51,000 male health care professionals that looked at the correlation between lifestyle (especially diet) and risk of various diseases. Of that entire group, the authors found 454 people who had their first heart attack between 1994 and 2004. The scientists then compared the vitamin D levels (measured as 25-hydroxy-vitamin D, or 25-OH-D) of these heart attack patients to the 25-OH-D levels of 900 similar men in the study who had never had a heart attack.

The average 25-OH-D level for the men in the study who had heart attacks was a little lower (23.0 ng/mL) than for men without heart attacks (24.5).

The most concerning finding, however, and the one that has already been widely reported in the news, is that men with the lowest levels of 25-OH-D-less than 15-were 2.5 times more likely to have a heart attack than were the men with levels above 30.

But that doesn't tell the whole story. One of the things that makes this a good study is that the authors tried to take into account many of the other known risk factors for heart attack, such as age, weight, smoking, diabetes, blood pressure, cholesterol, family history, and exercise level. After the researchers had adjusted for these factors, the average risk of heart attack for men with 25-OH-D levels below 15 came down to approximately twice that of men with levels above 30-about a 100 percent increase in risk.

It is important, too, to understand that this is only an estimate of the risk. Because only 454 men in the study (less than 1 percent) had heart attacks, the statistics suggest that the actual risk for men with very low 25-OH-D levels could be anywhere from as low as a 25-percent increased risk to as high as a 250-percent increased risk, compared to men who had vitamin D levels above 30.

For the more common case of mildly low levels of vitamin D-between 15 and 30-heart attacks were approximately 1,5 times more likely (a 50-percent increased risk). However, the statistical variation of this risk estimate was as low as zero (no increased risk) to as high as two-fold (a 100-percent increased risk).

Next, let's put this in perspective with other heart attack risk factors. Very low levels of 25-OH-D-below 15-are rare, but appear to double the risk of heart attack. Moderately low levels-between 15 and 30-cause a much smaller increase in the risk. By comparison, the traditional risk factors-like high blood pressure, smoking and diabetes-increase heart attack risks by 5 to 20 times.

So, if heart attack is your main concern, low vitamin D is a relatively minor issue and you'll benefit most by concentrating your efforts on controlling the major risk factors.

Keep in mind that this study did not show that taking extra vitamin D lowers heart attack risk. It is possible that the people in this study who didn't get heart attacks not only consumed more vitamin D but were also able to reduce their risk by starting to take statins to lower their cholesterol or by making other lifestyle changes.

We used to think we could reduce heart attack risk by giving women estrogen after menopause. There is still good data showing that lower estrogen levels correlate with higher risk of heart attack, but we've learned in recent years that taking extra estrogen does not reduce that risk very much, if at all.

In fact, the Women's Health Initiative (WHI) study, which played such a big role in changing our thinking about estrogen replacement, also looked at vitamin D supplements. Interestingly, the WHI found that taking extra vitamin D did not protect women against heart attacks. Another study showed that vitamin D supplements might reduce heart attack risk a little, but it was unable to prove definite benefit.

So what should you do with this information on vitamin D and heart attacks? We already know of several well established health risks of low vitamin D that are unrelated to the heart. I think it makes sense to measure your 25-OH-D level every year or two, and to try to keep the value above 35-40 ng/mL. Many people can do this by getting from 5 to 15 minutes of sun exposure to their face and arms every day (without sunscreen). It is also a good idea to take a supplement with 800-1,200 units of extra vitamin D every day.

But if you're really serious about reducing your risk of heart attack, your best bet is to start addressing the major issues like getting more exercise, losing weight, stopping smoking, and controlling your blood pressure, blood sugar, and cholesterol.