A study of postmenopausal women found no significant mortality benefit from vitamin D after controlling for health risk factors such as abdominal obesity. The only exception was that thin-waisted women with low vitamin D levels might have some increased risk.
The results agree with advice issued last year by the Institute of Medicine that cautioned against vitamin D having a benefit beyond bone health.
Doctors agree that vitamin D promotes bone health, but a belief that it can also prevent cancer, cardiovascular disease and other causes of death remains to be proven.
Now, a new study finds that vitamin D did not confer benefits against mortality in postmenopausal women after controlling for key health factors such as abdominal obesity.
The researchers say there's not enough evidence to do anything about vitamin D levels if it's not in regard to bone health.
In the study, researchers analyzed data from 2,429 postmenopausal women aged 50 to 79 who participated in the Women's Health Initiative study, a clinical trial that studied 36,000 women.
They tracked blood levels of vitamin D in the women and their risk of dying over a 10-year period. They not only looked at death from all causes but also focused on cancer and cardiovascular disease.
In all, 225 of the women died, including 79 from cardiovascular disease and 62 from cancer.
The researchers expected to find some protective effect against dying from these two causes from vitamin D. At first glance -- controlling only for age, ethnicity, and whether women took part in a calcium and vitamin D supplement trial -- that's what the data showed.
But after accounting for several more health factors such as smoking, history of cardiovascular disease, history of cancer, alcohol consumption, and waist circumference, the link between vitamin D levels and lower mortality risk disappeared.
The one exception was that women with thinner waistlines (less than 35 inches) and with the lowest vitamin D levels seemed to have a greater risk of dying from any cause within the 10-year study period.
The researchers can only speculate about why abdominal obesity was an especially important factor to control for in their analysis. Abdominal obesity is associated with several negative health indicators that may overwhelm any modest protective effect vitamin D might have.
They also point out that fat tissue can store vitamin D, possibly meaning that women with larger waistlines are storing more of the vitamin and less is available to be circulated in the blood to tissues.
A major new trial of vitamin D supplements and health called VITAL is getting underway and will likely provide answers about what vitamin D is good for.
For now, the researchers say there's not enough evidence to do anything about our vitamin D levels if it's not in regard to bone health.
Source: American Journal of Clinical Nutrition, October 2011
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.