Calcium and vitamin D are commonly taken by women as dietary supplements, possibly because of research going back to the 1980’s regarding an association with skeletal health. However, more recently the roles for calcium and vitamin D have widened as studies have uncovered novel physiological modifications caused by sub-clinical deficiencies. In particular, a growing body of evidence is linking vitamin D deficiencies to an increased risk of cancer, type 1 and type 2 diabetes and multiple sclerosis. Calcium is also currently being researched for its anti-obesity effects, with high intakes showing weight reduction properties. Significant interactions may also exists between the two nutrients beyond the well known regulation of skeletal health, especially as advances in molecular biology allow a greater understanding of cellular function. Because of this researchers are interested in understanding the benefits of calcium and vitamin D from dietary supplements.
For example, researchers1 have investigated the effects of calcium and vitamin D supplementation on subjects who were taking personal supplements of these nutrients, and those who were not. The data was taken from the Women’s Health Initiative, a clinical trial which had a 7 year randomised design, involving the daily co-administration of 1g of calcium and 400IU of vitamin D to 36,282 post-menopausal women. The results showed that those taking personal supplements of vitamin D and calcium, did not have reduced risk of developing cancer. In those subjects not taking personal calcium and vitamin D supplements, significant decreases in breast cancer, invasive breast cancer and total breast cancer of between 14 to 20%, were reported. There was also a non-significant reduction in colorectal cancer of 17%. Neither group experienced significant changes in mortality or risk of skeletal fractures.
As expected, those taking personal supplements of calcium or vitamin D did not gain a benefit from the addition of the 1g calcium and 400IU vitamin D supplement during the clinical trial. However, this provides more evidence that those individuals with sub-clinical deficiencies of certain nutrients gain benefits from supplementation. This also highlights the inadequacies of many people’s diet to supply the required amount of nutrients to prevent serious diseases. Although positive effects to supplementation were seen, the 7 year trial was still short when considering that the benefits of nutrients may take decades to manifest. Using clinical trials designed for assessing drugs to test nutrients is possibly a disservice to the field of nutrition and findings should always be interpreted with caution, especially considering the known synergism between vitamins and minerals and other nutrients.
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