Boston researchers are launching a large, national trial of vitamin D and fish oil to see if the dietary supplements make a difference in developing cancer or cardiovascular disease. They are also testing the idea that lower levels of vitamin D might explain higher rates of these diseases among black people.
Dr. JoAnn Manson and Dr. Julie Buring, both of Harvard Medical School and Brigham and Women's Hospital, hope to enroll 20,000 healthy older people in the federally funded trial. One quarter of the participants will be black. The researchers believe higher rates of cancer, heart disease, and stroke among black people, compared with whites, might be related to dark skin's lower ability to make vitamin D from absorbing sunlight, and they hope to learn whether taking vitamin D supplements could reduce or eliminate these disparities.
"African-Americans have a higher risk of vitamin D deficiency and a greater frequency of certain types of cancer and diabetes and hypertension, so I think that it will be of great importance to look at whether something as simple as taking a vitamin D supplement can narrow these health gaps," said Manson, who believes the study is one the first large scale randomized trials to target a specific group at higher risk for a deficiency of nutrients. "It would be wonderful if something as simple as a vitamin D pill could narrow that health gap."
Women over 65 and men over 60 with no history of cancer or cardiovascular disease will be randomly assigned into four groups. Some will take daily pills containing about 2000 international units of vitamin D and about 1 gram of fish oil. Others will take pills containing no active ingredients. In the two other groups some will take one real supplement and one placebo of vitamin D or fish oil.
The vitamin D doses are higher than what might be found in a multivitamin but the fish oil dose matches what the American Heart Association recommends, Manson said.
"I think it's important to be cautiously optimistic and not jump on the bandwagon to take megadoses of supplements before a clinical trial helps to clarify their role," she said. "There have been high hopes for many other nutrients and supplements in the past and the enthusiasm has dampened once these interventions are studied rigorously."
Vitamin E, vitamin C, beta carotene, folic acid, selenium, and other supplements have looked promising for disease prevention, but their benefits have not been borne out in large scale trials and some risk has been found with high levels.
Vitamin D was tested in the large Women's Health Initiative, but at a lower dose of 400 international units combined with calcium. Fish oil supplements of 1 gram have been studied in large trials, but only in people who had already suffered heart attacks or developed diabetes.
"What's most exciting is these low-cost supplements have the potential for a tremendous reduction in the burden of chronic disease in this country and throughout the world if they are shown to be effective," Manson said. "That's what this is all about: to get rigorous high-quality information about the balance between the benefits and risks of taking moderate to high doses of these supplements."
Recruitment begins in January for the $20 million trial, which is funded by the National Institutes of Health. Treatment will last five years. Participants will not need to travel to Boston because study forms and pills will be mailed, according to the web site for the study, called VITAL (VITamin D and OmegA-3 TriaL).
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