The idea made so much sense it was almost unquestioningly accepted: Vitamin D pills can protect bones from fractures. After all, the body needs the vitamin for the gut to absorb calcium, which bones need to grow and stay healthy.
But now, in the first large randomized controlled study in the United States, funded by the federal government, researchers report that vitamin D pills taken with or without calcium have no effect on bone fracture rates. The results, published Thursday in The New England Journal of Medicine, hold for people with osteoporosis and even those whose blood tests deemed them vitamin D deficient.
These results followed other conclusions from the same study that found no support for a long list of purported benefits of vitamin D supplements.
So, for the millions of Americans who take vitamin D supplements and the labs that do more than 10 million vitamin D tests each year, an editorial published along with the paper has some advice: Stop.
“Providers should stop screening for 25-hydroxyvitamin D levels or recommending vitamin D supplements and people should stop taking vitamin D supplements in order to prevent major diseases or extend life,” wrote Dr. Steven R. Cummings, a research scientist at the California Pacific Medical Center Research Institute, and Dr. Clifford Rosen, a senior scientist at the Maine Medical Research Institute. Dr. Rosen is an editor at The New England Journal of Medicine.
There are exceptions, they say: People with conditions like celiac or Crohn’s disease need vitamin D supplements, as do those who live in conditions where they are deprived of sunshine and may not get any of the mineral from foods that are routinely supplemented with vitamin D , such as cereals and dairy products.
Getting into such a severe vitamin D-deprived state is “very hard to do in the general population,” Dr. Cummings said.
The two scientists know that in making such strong statements they are taking on vitamin sellers, testing labs and advocates who have claimed that taking vitamin D, often in huge amounts, can cure or prevent a wide variety of ailments and even help people live longer.
Doctors often check for vitamin D levels as part of routine blood tests.
The study involved 25,871 participants — men aged 50 and older and women 55 and older — who were assigned to take 2,000 international units of vitamin D each day or a placebo.
The research was part of a comprehensive vitamin D study called VITAL. It was funded by the National Institutes of Health and began after an expert group convened by what is now the National Academy of Medicine, a nonprofit organization, examined the health effects of vitamin D supplements and found little evidence. The expert group’s members were supposed to come up with a minimum daily requirement for the vitamin but found that most clinical trials that had studied the subject were inadequate, making them ask if there was any truth to the claims that vitamin D improved health.
The prevailing opinion at the time was that vitamin D was likely to prevent bone fractures. Researchers thought that as vitamin D levels fell, parathyroid hormone levels would increase at a detriment to bones.
Dr. Rosen said those concerns led him and the other members of the National Academy of Medicine’s expert group to set what he called an “arbitrary value” of 20 nanograms per milliliter of blood as the goal for vitamin D levels and to advise people to get 600 to 800 international units of vitamin D supplements to achieve that goal.
Labs in the United States then arbitrarily set 30 nanograms per milliliter as the cutoff point for normal vitamin D levels, a reading so high that almost everyone in the population would be considered vitamin D deficient.
The presumed relationship between vitamin D and parathyroid levels has not held up in subsequent research, Dr. Rosen said. But uncertainty continued, so the National Institutes of Health funded the VITAL trial to get some solid answers about vitamin D’s relationship to health.
The first part of VITAL, previously published, found that vitamin D did not prevent cancer or cardiovascular disease in trial participants. Nor did it prevent falls, improve cognitive functioning, reduce atrial fibrillation, change body composition, reduce migraine frequency, improve stroke outcomes, protect against macular degeneration or reduce knee pain.
Another large study, in Australia, found that people taking the vitamin did not live longer.
Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Harvard Medical School and the leader of the main VITAL trial, said the study was so large it included thousands of people with osteoporosis or with vitamin D levels in a range considered low or ” insufficient.” That allowed the investigators to determine that they also received no benefit for fracture reduction from the supplement.
“That will surprise many,” Dr. Manson said. “But we seem to need only small-to-moderate amounts of the vitamin for bone health. Larger amounts will not confer greater benefits.”
The bone study’s first author and principal investigator, Dr. Meryl S. LeBoff, an osteoporosis expert at Brigham and Women’s Hospital, said she was surprised. She had expected a benefit.
But she cautioned that the study did not address the question of whether people with osteoporosis or low bone mass just short of the condition should be taking vitamin D and calcium, along with osteoporosis medications. Professional guidelines say they should take vitamin D and calcium, and she will continue to adhere to them in her own practice.
Dr. Dolores Shoback, an osteoporosis expert at the University of California, San Francisco, will also continue to advise patients with osteoporosis and low bone mass to take vitamin D and calcium.
It is “a simple intervention and I will continue to prescribe it,” she said.
Others go a bit further.
Dr. Sundeep Khosla, a professor of medicine and physiology at the Mayo Clinic, said that since vitamin D “will do little or no harm and may have benefits,” he would continue to advise his patients with osteoporosis to take it, recommending the 600 to 800 units a day in the National Academy of Medicine report.
“I will still tell my family and friends who don’t have osteoporosis to take a multivitamin a day to make sure they don’t get vitamin D deficiency,” he said.
Dr. Khosla follows that advice himself. Many multivitamin tablets now contain 1,000 units of vitamin D, he added.
But Dr. Cummings and Dr. Rosen remains firm, even questioning the very idea of a vitamin D deficiency for healthy people.
“If vitamin D doesn’t help, what is a vitamin D deficiency?” Dr. Cummings asked. “That implies you should take vitamin D.”
And Dr. Rosen, who signed off on the National Academy of Medicine report, has become a vitamin D therapeutic nihilist.
“I don’t believe any more in 600 units,” he said. “I don’t believe you should do anything.”