A new US review suggests that people with severe vitamin D deficiency have almost twice the mortality rate of those with vitamin D levels greater than 35 ng/ml.
The meta-analysis combined the results of 32 observational studies which examined a potential relationship between blood vitamin D concentrations and all-cause mortality rates (1). The analysis showed that out of the 32 studies, 25 found a significant relationship between higher vitamin D levels and a decreased risk for all-cause mortality. Those participants with vitamin D levels below 10 ng/ml had nearly twice the mortality rate of those with vitamin D levels above 35 ng/ml.
The researchers commented that the new findings agree with a National Academy of Sciences report, except the point for all-cause mortality reduction in the current analysis was greater than 30 ng/ml, rather than greater than 20 ng/ml. Recent studies have shown a relationship between higher vitamin D levels (75 nmol/L) and a reduced mortality risk among patients with colorectal and breast cancer (2). A meta-analysis of data from eight prospective cohort studies involving 26,018 men and women aged 50–79 years from Europe and the United States confirmed the same relationship (3).
A more recent study indicated that low vitamin D levels may have increased the risk of complications in 3,509 patients after non-cardiac surgery: Higher vitamin D levels were significantly related to decreased chance of morbidity and mortality. Between levels of 4 and 44 ng/ml, every 5 ng/ml increase in vitamin D status was associated with a 7% reduced risk of post-surgery complications such as in-hospital death, serious infections, and serious cardiovascular events (4). The researchers call for large randomized controlled trials to determine how vitamin D supplementation prior to surgery influences the rate of certain postoperative complications.