Vitamin D, nutrient that we can get for free when the sun’s rays hit our skin, has been associated with a reduction in risk of a wide range of health issues including heart disease, cancer, diabetes and multiple sclerosis. In theory at least, having high levels of vitamin D in the body should protect against these conditions, and as a result may also reduce risk of death. In a recent study published in the journal Clinical Endocrinology, researchers in Austria assessed the relationship between vitamin D levels and overall risk of death in a group of 614 men and women studied for an average of 6.2 years each [1].
In this study, individuals were split into four groups according to vitamin D levels. The individuals in the group corresponding to the lowest levels of vitamin D, compared to those with higher levels, were found to be at more than twice the risk of death. However, in an ‘epidemiological’ study of this nature, it is impossible to tell if lower levels of vitamin D actually increase the risk of death, or is just associated with it.
To help here, it is possible to ‘control for’ what are known as ‘confounding factors’. If the association between two factors (in this case, vitamin D levels and risk of death) remain after confounding factors are accounted for, then this makes a ‘causal’ relationship between two factors more likely.
In this particular study, the researchers went on to control for various factors including age, sex, presence of diabetes and high blood pressure, smoking habits and waist-to-hip ratio. Even after accounting for these factors, there was as still a statistically significant relationship between vitamin D levels and risk of death. And again, risk of death was roughly doubled in individuals with the lowest levels of vitamin D in their bodies.
This evidence supports the idea that higher vitamin D levels in the body can reduce the risk of death, but does not prove it. For that, we require intervention studies. Not so long ago, a study was published which grouped together 18 studies in which individuals had been treated with vitamin D or placebo over a period of time [2]. Despite relatively low levels of vitamin D supplementation, those taking this nutrient saw a small but statistically significant reduction in overall risk of death.
The current state of the evidence suggests that vitamin D has genuine life-saving properties. For many of us, the weather at this time of year can cause vitamin D levels to plummet. For information on how to maintain vitamin D levels through supplementation see here.
References:
1. Pilz S, et al. Vitamin D and mortality in older men and women. Clin Endocrinol (Oxf). 2009 Feb 18. [Epub ahead of print
2. Autier P, et al. Vitamin D supplementation and total mortality: a meta-analysis of randomized controlled trials. Arch Intern Med. 2007 Sep 10;167(16):1730-7.
