Vitamin D supplements, when given together with calcium, appear to be associated with lower mortality in older individuals, according to a new study.

Researchers at Aarhus University (Denmark), Ohio State University (OSU, Columbus, USA), and other institutions conducted a systematic literature search and meta-analysis of 24 randomized controlled trials reporting data on mortality, in which vitamin D was given either alone or with calcium. From a total of 13 trials with more than 1,000 participants each, eight trials were included in the analysis, for a total of 70,528 individuals (median age 70, 86.8% women). The researchers then calculated risk of death during three years of treatment in an intention-to-treat analysis, and performed a trial level meta-analysis including data from all studies.

The results showed that during the three years of treatment, 5.4% of the participants had died--5.3% of those receiving vitamin D with or without calcium and 5% of the controls. After adjustment for potential confounders, including incident hip and spine fractures, vitamin D supplementation with or without calcium was associated with a 7% lower mortality risk. A deeper look showed that the reduction was significant for those taking calcium and vitamin D together, but not for those taking vitamin D alone. The study was published early online on May 17, 2012, in the Journal of Clinical Endocrinology & Metabolism.

“Calcium supplementation could reduce recurrence of colorectal adenomas and thus colorectal cancer and mortality, an effect that may be strengthened if vitamin D is also provided,” concluded lead author Lars Rejnmark, MD, PhD, and colleagues. “Calcium and vitamin D may reduce the risk of cancer, particularly breast and colorectal cancer.”

Vitamin D is a group of fat-soluble secosteroids found in many dietary sources, such as fish, eggs, fortified milk, and cod liver oil. Although vitamin D is commonly called a vitamin, it is not actually an essential dietary vitamin in the strict sense, as it can be synthesized in adequate amounts by all mammals from sunlight. The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus.

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