The case for vitamin D supplementation keeps getting weaker and weaker. The nutrient—hailed almost as if it had superpowers—has failed yet again to live up to its disease-busting expectations.
This time, Tufts Medical Center researchers found that vitamin D didn’t work against knee pain caused by arthritis when it was tested against a placebo in a clinical trial published in the Journal of the American Medical Association.
Other recent studies found that vitamin D supplements don’t protect against colds or prevent osteoporosis in healthy women. (The only benefit seen for the nutrient in clinical trials so far was for preventing falls in seniors.)
The hype over vitamin D as a super-nutrient—that protects against everything from cancer to heart disease to multiple sclerosis—stems from population studies linking low vitamin D levels in the blood with an increased risk of disease and overall poor health. But those studies couldn’t prove that taking vitamin D actually could prevent health problems.
Hence the need for clinical trials that randomly assigned people to either take the supplement or a placebo.
In this latest study, the researchers left no stone unturned. They gave a high amount of vitamin D to the treatment group, at least 2,000 international units per day, which is far higher than the recommended daily amount of 600 to 800 IUs. They also tested vitamin D blood levels in those who were getting the supplements and increased supplementation up to 8,000 IUs per day if the blood levels didn’t rise enough with the lower supplement.
“We made sure that we gave everyone enough to get their levels up to a value that would be considered sufficient to help with their arthritis,” said study co-author Timothy McAlindon, head of rheumatology at Tufts Medical Center.
Unfortunately, those who took the vitamin D supplements had similar changes in their knee cartilage on imaging tests—a way to monitor arthritis—and had the same improvement in pain compared to those who took placebos.
McAlindon said he started taking a vitamin D supplement a few years ago after all the hype started over the nutrient. Now, he’s no longer taking it. “I’m becoming a bit of a supplement skeptic,” he told me. A good lesson for us all.