Study shows both significant benefits and risks of vitamin D3 and calcium supplementation.
The recent Women’s Health Initiative trial showed a 7% reduction in cancer mortality for those taking vitamin D3 and calcium supplements.
However, the US study also showed that this supplementation regimen led to a 6% increase in cardiovascular disease deaths. So, in the end, there was no net benefit.
The study, the largest randomised multicentre clinical trial of daily calcium and vitamin D supplementation to date, included over 36,000 post-menopausal women with no history of breast or colorectal cancer, given either placebo or 1000mg of calcium carbonate (400mg of elemental calcium) with 400 IU of vitamin D3 for an average of seven years.
Over the average 22-year follow up, researchers found no significant difference in all-cause mortality between the placebo and treatment groups.
“Although the reduction in cancer mortality is clinically large, it is offset by the increase in CVD mortality, resulting in net zero benefit in terms of mortality,” Professor Adrian Esterman, epidemiologist and professor of biostatistics at the University of South Australia, told The Medical Republic.
It was found that the reduced risk of cancer mortality was more pronounced in women who had been using calcium and vitamin D supplementation prior to the study, although often at smaller doses than in the study.
“[The authors] suggest that [calcium and vitamin D] supplementation may affect cancer biology primarily in the setting of augmenting an insufficiency in nutrient status,” Professor Esterman explained.
“GPs need to give careful thought before recommending this supplementation.”
