NEW YORK • In recent years, many people have embraced vitamin D and fish oil pills.
A steady trickle of research studies have linked higher levels of vitamin D with lower rates of cancer and other ills, and fish consumption with reduced heart disease.
But a large and rigorous government-funded trial has found the supplements do not lower cancer rates in healthy adults.
Nor do they reduce the rate of major cardiovascular events, a composite of heart attacks, strokes and deaths from cardiovascular disease.
"It's disappointing, but there have always been such high expectations that vitamin D can do all these different things," said Dr Clifford Rosen of the Maine Medical Centre Research Institute. He is an author of an editorial on the studies in The New England Journal Of Medicine.
"In terms of preventing cancer, I think the door is closed.
"I don't think there is anything there," he noted.
The study also showed that omega-3 fatty acid supplements do not reduce major cardiovascular events, he said. "That's what people should take home with them."
The results hinted at some potential benefits, which would have to be explored in separate trials.
Secondary analysis of the data found, for example, a reduction in cancer deaths for people who took vitamin D for at least two years and fewer heart attacks in people who took fish oil.
And people do need vitamin D in order to absorb calcium and for other bodily functions.
Regarding fish oil, Dr Rosen asked: "Are there subgroups where it may be effective or reduce heart attacks? It's possible.
"But that's got to be proven in another trial. If this were a drug being tested for approval by the Food and Drug Administration, it wouldn't make it."
Dr JoAnn Manson, an investigator at Brigham and Women's Hospital who led the trial, said that since fish oil did not reduce strokes, it did not have an impact on the overall risk of cardiovascular disease.
But she said another analysis looking separately at heart attacks found a 28 per cent reduction among those taking fish oil, a 40 per cent reduction in people who eat little fish and a 77 per cent reduction in African-Americans.
"The data has to be very strong before you go out and recommend to everyone in the world to take supplements and we're certainly not doing that," Dr Manson said.
"We're saying: 'Talk to your doctor, especially if you have low fish intake or are African-American.'"
The National Institutes of Health funded the trial, which recruited 25,871 healthy American men and women aged 50 or older, including 5,106 African-Americans.