About the Study | How Does This Affect You?

For more than 60 years, studies have suggested that being in the sun may reduce the risk of dying from cancer (other than skin cancer). More recent research indicates that people with higher levels of vitamin D in their blood are less likely to develop certain cancers. Similar associations have been made between higher levels of calcium in the diet and reduced cancer risk.

A study in the June 1, 2007 issue of the American Journal of Clinical Nutrition found that women who took vitamin D and calcium supplements were 60% less likely to develop cancer than those who took a placebo.

About the Study

This study included 1,179 healthy postmenopausal women aged 56 and older. The women were assigned to one of three groups: the first group took 1,400-1,500 milligrams (mg) of calcium each day, the second took calcium plus 1,100 international units (IU) of vitamin D each day, and the third took placebo, or "sham," pills. The researchers followed the women for four years and tracked whether they developed cancer.

During the study, 50 women developed cancers other than skin cancer. Compared with the women taking the placebo, the women taking calcium plus vitamin D had a 60% lower risk of developing cancer. The women taking calcium only had a 47% lower risk of developing cancer compared with those taking a placebo, but that finding was not statistically significant.

One weakness of the study is that it did not distinguish between different types of cancer.

How Does This Affect You?

This study suggests that vitamin D and calcium supplementation may reduce the risk of cancer, at least in postmenopausal women. This adds to the evidence that vitamin D may help prevent cancer. Another large study, the Women's Health Initiative (WHI), reported no significant link between taking vitamin D supplements and developing colorectal cancer. But the dose of vitamin D was much lower in the WHI study (400 IU per day). More studies are needed to clarify the role of calcium and/or vitamin D supplements in cancer prevention.

In addition to potentially reducing your risk of cancer, calcium and vitamin D can help protect your bones. You can get calcium and vitamin D in your diet. Dairy products and leafy green vegetables are rich in calcium, and vitamin D can be found in oily fish and fortified milk and cereals. Another way to get vitamin D is to spend 10-15 minutes in the sun 2-3 times per week before applying sunscreen. Talk with your doctor to find out if you are getting enough calcium and vitamin D in your diet and from the sun. If you aren't, supplements may benefit you.