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Vitamin D and omega-3 fatty acid supplements have had mixed results in preventing heart attacks, strokes, and cancer in people who have developed these problems or who are at high risk. However, a new study published online November 10, 2018 by the New England Journal of Medicine found that they may actually prevent these conditions in people who have never had these problems.

The researchers recruited nearly 26,000 people ages 50 and older who had no history of heart disease or cancer. The participants were divided into four groups. People in one group were given daily doses of 2,000 international units of vitamin D (an amount that has been linked to a lower risk of disease in observational studies) and 1 gram of a drug called Lovaza, which contains 840 milligrams of omega-3 fatty acids (two to one) four times as much as two servings of fish a week). The second group took vitamin D and a placebo, the third group took the omega-3s and a placebo, and the last group took two placebos. After more than five years, the researchers found that those given omega-3s were 28% less likely to have a heart attack than those given a placebo. Those who ate fewer servings of fish (less than the average of 1.5 servings per week) appeared to get more benefit from the extra omega-3s, while those with a higher fish intake had minimal benefit.

The study also found that those who took vitamin D supplements alone had no lower rates of heart attack, stroke, or cancer. In people who later developed cancer, those who took vitamin D supplements for at least two years were 25% less likely to die from cancer than those who received a placebo.

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