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By Gene Emery
(Reuters Health) – A large US study designed to evaluate the health benefits of vitamin D and fish oil supplements concludes that omega-3 oil can significantly reduce the risk heart attack, while the benefits of vitamin D seem to come from a reduced risk of death from cancer.
Neither vitamin D nor fish oil reduced the risk of stroke or cancer at the start of the trial, whose participants did not know if they were taking the real ones. supplements or a dummy pill.
The rate of heart attack in vessels containing fish oil was 28% lower than those who received the dummy pill, or placebo, and 77% lower in African American participants – although the lead author of the study told Reuters Health that this dramatic fall in risk among black participants needs to be confirmed.
For people taking vitamin D and developing cancer, the cancer death rate was 25% lower, probably because the vitamin "may affect the biology of the tumor and is therefore less likely to spread and become metastatic. "said Dr. JoAnn Manson, lead author chief of the Division of Preventive Medicine at Brigham and Women's Boston Hospital.
"As a result, you may see a reduction in the number of cancer deaths, but not a reduction in the first diagnosis, which may require a much longer test," she said in an interview. telephone. "If you talk about cancer prevention, it can take more than ten years of treatment."
It took a few years of vitamin D use to make the reduction in cancer deaths clear.
The findings were reported Saturday at the American Heart Association's scientific meeting in Chicago and online in the New England Journal of Medicine.
Both supplements have a reputation for being beneficial based on animal testing and observational studies conducted with diverse populations or ethnic groups. But large studies that directly test the benefits of vitamin D and fish oil in supplement form have yielded inconsistent results.
The new study, known as VITAL, is the first large-scale test in the general population. Most previous research has focused on volunteers with a high risk of heart attack, stroke and / or cancer.
The researchers donated 2,000 international units of vitamin D per day, 1 gram of marine omega-3 fatty acids or placebo supplements to 25,871 volunteers aged 50 and over. None had a history of cancer, heart attack or stroke. At least half remained in the study for more than five years.
On the basis of new findings, "people who are already taking vitamin D or fish oil will have no reason to quit," Manson said.
Others may want to wait "because we will publish the results for other evaluation criteria – diabetes, cognitive function, depression, autoimmune diseases – over the next six months" , she said. "These findings could help people decide if the benefits outweigh the risks they run."
And people should not take higher doses than those used in the study, noted Manson. With megadoses, "the risk may outweigh the benefit.With high doses of vitamin D, there may be a risk of high levels of calcium in the blood.Some have suggested a higher risk of cardiovascular disease , falls and even fractures ".
By other measures, neither of the two supplements seemed useful.
Among fish oil recipients, all-cause death rates, cancer and heart disease rates in general were not significantly different from those of people not taking fish oil supplements .
In addition, the collective probabilities of experiencing a heart attack, stroke, or death, regardless of the cause, were essentially the same whether patients were taking fish oil or a placebo .
A benefit was made when researchers unraveled individual elements of heart disease, such as the rate of heart attacks, the rate of fatal heart attacks and the need for angioplasty.
Even a little fish oil seemed to help. Volunteers who consumed less than average fish – less than a half and a half a week – and received the true omega-3 supplements reduced the risk of heart attack by 40%.
In the study on vitamin D, which was "the largest randomized high-dose vitamin D trial in the world," according to Manson, the recipients of supplements and non-supplements had similar rates of heart attack, from Stroke, death by heart attack and breast, prostate or colon and rectum cancers.
Only the chances of dying from cancer have been reduced.
SOURCES: https://bit.ly/2PP7RT2, https://bit.ly/2FcO2Ba and https://bit.ly/2OCRoN3. The New England Journal of Medicine, online November 10, 2018.
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