Twenty-six percent of Americans age 60 and older take vitamin D supplements, according to a 2017 study. Twenty-two percent take pills containing omega-3 fatty acids, a key ingredient in fish oil.

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

That’s 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 supplements of 2,000 international units a day, equal to one or two of the vitamin D pills typically sold in stores.

Vitamin D testing has become a 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 percent since 2007 – at a cost of $365 million.

“It’s time to stop” vitamin D testing, Rosen said. “There’s no justification.”

Dr. JoAnn Manson, the study’s lead author, agrees that her results don’t support screening healthy people for vitamin D deficiency. But she doesn’t 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’re already taking fish oil or vitamin D, our results would not provide a clear reason to stop,” Manson said.

Manson notes 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 percent, Manson said.

As for vitamin D, it appeared to reduce cancer deaths – although not cancer diagnoses – by 25 percent.

But slicing the data into smaller segments – with fewer patients in each group – can produce unreliable results, said Dr. Barnett Kramer, director of the cancer prevention division at the National Cancer Institute.

The apparent links between fish oil and heart attacks – and vitamin D and cancer death – could be due to chance, Kramer said.

Experts agree that vitamin D is important for bone health. Researchers in these papers didn’t report on its effect on bones in these papers. Instead, they looked at areas where vitamin D’s benefits haven’t been proved, such as cancer and heart disease.

Preliminary studies have suggested vitamin D can prevent heart disease and cancer, but more rigorous studies have disputed those findings.

Manson and her colleagues plan to publish data on the supplements’ effects on other areas of health, including diabetes, memory and mental functioning, autoimmune disease, respiratory infections and depression, in coming months.

Consumers who want to reduce their risk of cancer and heart disease can follow other proven strategies.

“People should continue to focus on known factors to reduce cancer and heart disease: Eat right, exercise, don’t smoke, control high blood pressure, take a statin if you are high risk,” said Dr. Alex Krist, a professor of family medicine and population health at Virginia Commonwealth University.