Low Vitamin D Levels Again Linked to Higher Death Risk
Lee Swanson Research Update
Low levels of vitamin D may increase the risk of dying from all causes by 150%, suggests a study involving over 700 elderly women.
Women with blood levels of the vitamin lower than 15.3 nanograms per milliliter were more likely to die from causes such as heart disease and cancer than women with higher levels (above 27 ng/ml), according to findings published in Nutrition Research.
"The present findings from this population-based cohort of aging are consistent with the association between low serum 25(OH)D and mortality that has been described in […] the general population," wrote the researchers, led by Richard Semba from Johns Hopkins University.
"In addition, a recent meta-analysis suggested that vitamin D supplementation was associated with decreased mortality," they added.
The researchers noted that several biological mechanisms could explain a causal relationship between vitamin D deficiency and mortality, with the vitamin’s active form (1,25-dihydroxyvitamin D) linked to a range of effects including control of inflammatory compounds, regulating immune health and blood pressure, or reducing arterial hardening.
"The role that vitamin D plays in different tissues may account for the associations between vitamin D deficiency and cardiovascular disease, cancer and mortality," they said.
The general population study used data from 13,331 men and women participating in the Third National Health and Nutritional Examination Survey (NHANES III). The results of the study grabbed headlines around the world when published last year in the Archives of Internal Medicine.
The new study looked at vitamin D levels in the form of 25-hydroxyvitamin D (25(OH)D)—the non-active "storage" form—in 714 community-dwelling women, aged between 70 and 79 years, participating in the Women’s Health and Aging Studies I and II.
During six years of follow-up, 100 of the 714 women died with data showing that the main causes of death included cardiovascular disease (36%), respiratory disease (18%), cancer (15%), and other causes (27%), state the researchers.
When the researchers divided the women into four groups (quartiles) according to their 25(OH)D levels, the proportion of women who died during those six years in each quartile was 19, 13, 15 and 8.1%, said the researchers.
Increasing blood levels of vitamin D were linked to increasing survival rates, with women with the lowest average 25(OH)D levels having "significantly worse survival" than women with the highest average levels of 25(OH)D.
Nutrition Research 29(8):525-530, 2009