Vitamin D doesn't prevent heart attack or cancer

Among seniors with a high risk of bone fractures, taking vitamin D or calcium pills has no impact on their chances of dying from cancer or vascular disease, researchers say in a new study.

Vitamin D is considered beneficial for bone health, and earlier studies have found that having low vitamin D levels in the blood is tied to a greater chance of dying from heart problems (see Reuters Health reports of November 25, 2011 and June 24, 2011).

The thinking, therefore, has been that taking extra vitamin D might cut that risk.

"There's a lot of interest in vitamin D preventing heart disease and cancer, but the evidence from randomized trials is weak," said Dr. Alison Avenell, the lead author of the study and a researcher at the University of Aberdeen in England.

In the latest study, published in the Journal of Clinical Endocrinology and Metabolism, the researchers tracked the health of nearly 5,300 people over age 70 who had had a bone fracture.

The participants were randomly divided into four groups: one took 800 IU (International Units) of vitamin D daily, the second group took 1000 milligrams of calcium each day, a third group took both supplements, and a fourth group took fake pills that looked like the supplements.

Vitamin D is essential for the formation, growth, and repair of bones and for normal calcium absorption and immune function. It is obtained primarily through exposure of the skin to ultraviolet radiation in sunlight, but it can also be obtained from some foods and dietary supplements.

Some studies suggest that higher intakes of vitamin D from food and/or supplements and higher levels of vitamin D in the blood are associated with reduced risks of colorectal cancer; however, the research results overall have been inconsistent.

Whether vitamin D is associated with reduced risks of other cancers, including breast, prostate, and pancreatic cancers, remains unclear.

The National Cancer Institute (NCI) does not recommend for or against the use of vitamin D supplements to reduce the risk of colorectal or any other type of cancer.

People in the study took the pills for two to five years, and were followed for up to three years afterward.

Among people who took vitamin D, 32 out of every 100 died during the study, while 33 out of every 100 people who did not get the supplement died. That small difference could easily have been due to chance, the researchers found.

There were no differences in deaths from cancer or heart disease either. Calcium also proved unhelpful.

A recent analysis of 50 studies on vitamin D and heart health found no impact from taking the vitamin (see Reuters Health report of July 11, 2011).