Vitamin D helps heart patients survive

Lei Dai, Man Liu and Liangkai Chen were able to follow 37,079 middle-aged heart patients for almost 12 years. The study participants had a history of heart attack or stroke, or suffered from heart failure or atrial fibrillation. During that period, 6,319 patients died, and these were strikingly often patients with low vitamin D levels in their blood.

The more vitamin D the study participants had in their blood, the lower their risk of death. For every 10 nanomoles/L increase in vitamin D levels, the risk of death decreased by 12 per cent, according to the researchers' calculations. This is probably because both blood vessels and the heart muscle need vitamin D to stay healthy and flexible.

Most heart patients had too little vitamin in their blood. Sixty percent of the study participants had vitamin D levels below 50 nanomoles/L. Doctors and nutritionists consider this to be the minimum level a healthy individual should have. But in most countries in the Northern Hemisphere, such low levels are normal. More than half of the Dutch population has vitamin D levels below 50 nanomoles/L during the winter months. That sounds alarming, and of course it is.

The Endocrine Society, a global organisation of endocrinologists, believes that everyone should have a vitamin D level of at least 75 nanomoles/L. In the Chinese study, only 11.6 percent of British heart patients had such an excellent vitamin D level.

The researchers used statistics to eliminate the effect of as many other factors as possible. By correcting for the impact of diabetes, obesity, medication use, smoking, alcohol and other lifestyle factors, the researchers believe that their study truly reflects the influence of vitamin D. They are not 100% certain of this, however. Another type of study is needed for that: an intervention study in which subjects are given vitamin D supplements or treated with UVB light.