A recent study that is prevalent on the Internet related to Vitamin D and Heart Attacks. Published online, ahead of print in the American Hear Association's journal Circulation, the study looks at the sons and daughters from the famous Framingham study who had not a heart attack and measured their levels of vitamin D. They found that of 1739 patients studied over 5 years, there were 120 heart attacks. People with low levels of vitamin D were 62% more likely to get a heart attack than people with normal levels of vitamin D. Does this mean that you should book your next trip to the Caribbean to soak in the rays?
One of the problems with medical news in the media is confusion between association and causation. This study showed that people with heart attacks are more likely to low levels of vitamin D, not that taking in more vitamin D will prevent heart attacks. Physicians have been burned by this in the past. With regards to heart attacks, homocysteine is a great example. Observational studies like the vitamin D study showed that low levels of homocysteine were associated with increased heart attacks. In addition, we new that taking folic acid (which is very important in preventing birth defects in pregnant women) increases levels of homocysteine. So naturally, taking folic acid prevents heart attacks, right? Wrong. When studied prospectively (given half the agent and half a placebo), though folic acid raised homocysteine, it did not prevent heart attacks, and in fact may have increased the risk.
The same is true of other supplements, which I have mentioned on this blog previously.
So why would low levels of vitamin D be associated with heart attacks if they don't cause them? This is known as a marker for disease. One of the ways we get vitamin D is by exposure to sunlight. Perhaps people who were more active, and more likely to be outside, had higher levels of vitamin D and lower risks of heart attacks?
The point is that just because a study says that something is associated with a disease doesn't mean that it will cause/prevent it. Vitamin D (and calcium) are very important for bone health. The National Osteoporosis Foundation has a great page on recommended daily amounts of vitamin D and calcium. As far as preventing heart attacks, you need to stop smoking, become physically active, lower your blood cholesterol, and control diabetes and high blood pressure if you have it. For patients at high risks medications to lower cholesterol and aspirin are very helpful. The American Heart Association has very good information on this.