Vitamin D link to winter heart disease challenged

Research from the University of Dundee has challenged the view that a lack of sunshine increases the incidence of heart disease in winter.

The study, published in the International Journal of Epidemiology, indicates that vitamin D is unimportant in cardiovascular disease.

Vitamin D was first linked to heart-related winter deaths in 1981.

Researchers have now suggested lack of vitamin D is the result of other risk factors, not itself a cause of risk.

NHS advice is that people get most of their vitamin D from exposure to sunlight.

The study involved international collaboration in which stored blood from patients was tested in Germany to check for any association between levels of vitamin D and heart-related winter deaths.

It found the lowest levels of the vitamin tended to occur in March, after the peak of winter deaths.

Author Prof Hugh Tunstall-Pedoe said: "This is a major study, in a population with two-to-one seasonal changes in vitamin D, and low levels overall. If vitamin D deficiency were a major cause of heart disease and death, we would have expected it to show up. But it did not.

"So our results seriously challenge its alleged role.

"We want others to explore seasonal change as we have done - a huge natural experiment which comes for free.

"All of this was made possible by the co-operation of healthy Scottish volunteers, by continuing access to their records, and by Scottish, United Kingdom, and European Commission funding at different times over many years."

The research was part-funded by the British Heart Foundation (BHF).

BHF associate medical director Prof Jeremy Pearson said: "We've known for many years that a low level of vitamin D is associated with an increased risk of cardiovascular disease, but it was not clear whether lack of vitamin D directly causes the increased risk or is a consequence of other factors.

"The long-term Scottish Heart Health Study, which the BHF helped to fund, has provided a series of valuable insights over the years and they have now shown that low vitamin D is result of other risk factors, rather than a cause of increased risk."