The National Institutes of Health funded the trial, which hired 25,871 healthy American men and women aged 50 and over, including 5,106 African Americans. Participants in the study were divided into four groups and were randomly assigned to supplements or placebo and were followed for 5.3 years on average.
One group received 2,000 IU (international units) of vitamin D3 and 1 gram of omega-3 each day. A second group was given vitamin D and a virtual pill instead of omega-3. A third group took omega-3 and a vitamin D placebo. And the final team received two placebo.
Pharmavite LLC, Northridge, Calif., Donates vitamin D and placebo agents, while Pronova BioPharma of Norway and BASF donated Omacor, a fish oil sold under the brand name Lovaza in the United States.
The results, published in The New England Journal of Medicine, are presented Saturday at a conference of the American Heart Association in Chicago.
In many ways, the results are not surprising. The public has been plagued by a steady stream of information on the health benefits of vitamin D in recent years, as studies have linked low levels of vitamin in conditions as diverse as diabetes, high blood pressure, cancer, heart disease and the Depression. Many primary care physicians typically test the patient's vitamin D levels and declare them inadequate and supplementary sales have soared over the past few years.
However, critics have questioned whether vitamin D is simply an indicator of overall health and whether the threshold for deficiency was too high. So-called sunbathing vitamin is synthesized in the body when the skin is exposed to sunlight and is depleted by smoking, obesity, poor nutrition and other factors. Some foods, such as fatty fish, eggs and fortified milk, also contain vitamin D.
The Institute of Medicine in 2011 concluded that most Americans have enough vitamin D and that deficiencies have been exaggerated. The team also noted that reports of potential benefits with higher blood levels were inconsistent.