Posted on Jun 03, 2013, 6 a.m.
A group of researchers from Israel claim to have established an upper safe limit for vitamin D, the so-called sunshine vitamin.
Vitamin D deficiency is known to be deleterious to health and has been linked to cardiovascular events and mortality, yet studies have found that supplementation either fails to decrease mortality or cardiovascular events or only has a small positive effect. Yosef Dror, PhD, of Hebrew University in Rehovot, Israel, believes that these “unpredictable results” may be due to the misconception that a high dose of vitamin D would be more effective than a moderate dose. The researchers conducted a study of 422,000 people aged 45-years or older, who underwent vitamin D blood assays. The results showed, for the first time, that the safe range of vitamin D levels with respect to coronary morbidity and mortality lies between 20 to 36 ng/mL. Vitamin D levels both below and above this range were associated with a significant increase in mortality and morbidity. More than 60% of participants were found to have insufficient blood levels of vitamin D, and half of these participants had severely low vitamin D levels. Too little vitamin D was associated with a 1.5-times increased risk of acute coronary morbidity or mortality. On the other end of the scale, 3% of participants had elevated vitamin D levels (>36 ng/mL), which was associated with a 1.13-times elevated risk of coronary morbidity or death. Yror warns that there is a risk that some people who are already within the upper-normal range, may actually increase their risk of morbidity and mortality by taking supplementary vitamin D. However, he adds that vitamin D supplementation, with strict monitoring to avoid overload, may have a significant influence on public health.
Yosef Dror, Shmuel Giveon, Moshe Hoshen, Ilan Feldhamer, Ran Balicer, Becca Feldman. Vitamin D Levels for Preventing Acute Coronary Syndrome and Mortality: Evidence of a Non-Linear Association. J Clin Endocrinol Metab. 2013 Mar 26. [Epub ahead of print]