Vitamin D Blog: Do Low Levels Raise Cancer Death Rates?
Published: Jun 17, 2014
By Parker Brown

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Low levels of vitamin D were associated with higher cancer mortality in people with a history of cancer, a study found.

Based on a meta-analysis, low 25(OH) vitamin D levels were tied to a risk ratio of 1.70 (95% CI 1.00-2.88) in cancer patients with a disease history. Inadequate vitamin D levels also were linked to an increase in all-cause mortality (RR 1.57, 95% CI 1.36-1.81) and cardiovascular mortality (RR 1.41, 95% CI 1.18-1.68), reported Ben Schöttker, PhD, of the German Cancer Research Center in Heidelberg, and colleagues in BMJ.

However, an increased risk of cancer mortality was not observed in patients with no history of cancer and low vitamin D levels (RR 1.03, 95% CI 0.89-1.20), Schöttker’s group stated.

In a separate study in the British Journal of Cancer, researchers found that vitamin D reduced total cancer mortality by 12%, but did not affect total cancer incidence.

Schöttker’s group looked at eight prospective cohort studies from the U.S. and Europe on serum vitamin D concentrations in more than 26,000 men and women (ages 50 to 79). They said their results were consistent even as the vitamin D levels varied greatly across populations, sexes, age groups, and seasons of blood draw.

“Overall, this finding may support the view that low vitamin D concentrations might be a marker for a poor health status rather than a cause of premature mortality,” Schöttker’s group wrote.

They cautioned that the meta-analysis was observational and did not consider confounders such as impairments of the immune system.

For the second study, Nana Keum, from the Harvard School of Public Health, and Edward Giovannucci, MD, ScD, of Brigham and Women’s Hospital, both in Boston, performed a meta-analysis of four randomized controlled trials measuring cancer incidence. Three of the studies also measured mortality over a period of 2 to 7 years.

Previous research has shown that at least 15 types of cancers have been linked to a lower sun exposure, and that vitamin D more strongly affects cancer mortality than it does incidence, the authors said.

They reported that vitamin D supplementation (400-1,100 IU/day), had little effect on total cancer incidence (summary relative risk [RR] 1.00, 95% CI 0.94-1.06), but significantly reduced total cancer mortality (400-833 IU/day, summary RR 0.88, 95% CI 0.78-0.98).

The analysis covered a short time period and inherited the limitations of the original randomized controlled trials, which didn’t include cancer instances or mortality as primary endpoints. And only one of the four randomized controlled trials examined vitamin D-only supplementation — the rest also included calcium supplements.

It was unclear during which stages of cancer treatment the potential benefits of vitamin D operate in, the researchers added.

Have a tip on a vitamin D study? Email Kristina Fiore at k.fiore@medpagetoday.com. You can also catch our vitamin D feed on Twitter, @vitaminDblog.

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