A widely anticipated study has concluded that neither vitamin D nor fish oil supplements prevent cancer or serious heart-related problems in healthy older people, according to research presented Saturday at the American Heart Association Scientific Sessions. 

Researchers defined serious heart problems as the combined rate of heart attacks, stroke, and heart-related deaths. Although hundreds of studies of these supplements have been published over the years, the new clinical trial a federally funded project involving nearly 26,000 people is the strongest and most definitive examination yet, said Dr. Clifford Rosen, a senior scientist at the Maine Medical Center Research Institute who was not involved in the research.

Vitamin D supplements

Doctors have been keenly interested in learning the supplements' true value, given their tremendous popularity with patients. 2017 study found that 26% of Americans age 60 and older take vitamin D supplements, while 22% take pills containing omega-3 fatty acids, a key ingredient in fish oil.

The new study also suggests there is no reason for people to undergo routine blood tests for vitamin D, said Rosen, who co-wrote an accompanying editorial. (Both were published in the New England Journal of Medicine.).

That is because the study found that patients' vitamin D levels made no difference in their risk of cancer or serious heart issues, Rosen said. Even people who began the study with clear vitamin D deficiency got no benefit from taking the supplements, which provided 2,000 international units a day. This amount is equal to one or two of the vitamin D pills typically sold in stores.

A recent Kaiser Health News story reported that vitamin D testing had become a too huge business for commercial labs – and an enormous expense for taxpayers. Doctors ordered more than  10 million vitamin D tests for Medicare patients in 2016  – an increase of 547% since 2007 –at the cost of $ 365 million.

"It Is time to stop it," said Rosen of vitamin D testing. "There is no justification." Dr. JoAnn Manson, the study's lead author, agrees that his results do not support screening healthy people for vitamin D deficiency. But she does not see her study as entirely negative.

Manson notes that her team found no serious side effects from taking either fish oil or vitamin D supplements. "If you are taking fish oil or vitamin D, our results will not provide a clear reason to stop," Manson said. He noted that a deeper look into the data suggested possible benefits.

When researchers singled out heart attacks rather than the rate of all serious heart problems combined they saw that fish oil appeared to reduce heart attacks by 28%, Manson said. As for vitamin D, appeared to reduce cancer deaths although not cancer diagnoses by 25%.