Taking this popular vitamin won't protect your bones, study finds

Taking a higher dose of vitamin D to protect your bones isn't necessary if you are a healthy middle-aged or older adult with no existing bone disease or vitamin D deficiency, a new study found. Vitamin D is needed by the body to fully absorb calcium and phosphorus from food.

Taking 2,000 IU (international units) a day of supplemental vitamin D3 without calcium over the course of more than five years did not reduce hip, wrist or pelvic fractures when compared with taking a daily placebo, according to the study published Wednesday in The New England Journal of Medicine.

A placebo is a sham pill given to patients so they will believe they are getting the real treatment.

"This is the largest, longest, randomized controlled trial on vitamin D supplementation in the US -- 25,871 men and women were enrolled from all 50 states, including 20% Black participants," said study author Dr. Meryl LeBoff, chief of the calcium and bone section in the Endocrinology, Diabetes and Hypertension Division at Brigham and Women's Hospital in Boston.

"Overall, the results from this large clinical trial do not support the use of vitamin D supplements to reduce fractures in generally healthy US men and women," said LeBoff, also a professor of medicine at Harvard Medical School.

"The study validity is excellent. It is in alignment with previous data showing that a population unselected for vitamin D deficiency does not benefit from vitamin D supplementation," said Dr. Anne Rentoumis Cappola, a professor of medicine in the Division of Endocrinology, Diabetes, and Metabolism at the University of Pennsylvania's Perelman School of Medicine in Philadelphia.

"Randomized clinical trial data are the highest level of data and those have repeatedly failed to show benefit from any vitamin when given to an unselected study population," said Cappola, who was not involved in the study.

Doesn't apply to everyone

However, the study results would not apply to people with a severe vitamin D deficiency, LeBoff said. Nor does it apply to anyone with low bone mass, which is less than optimal bone mineral density, or osteoporosis, a bone-thinning disease that causes bones to become so brittle that a fall or even a mild stress might cause a fracture.

"This is a major public health problem in the US. One out of two women age 50 and older will develop an osteoporosis-related fracture in their remaining lifetime," LeBoff said. "It's really important that patients with osteoporosis be evaluated for the many underlying factors that contribute to osteoporosis to see if there's any reversible causes."

The study results also don't apply to elderly in nursing homes, LeBoff said, because of the unique factors that apply to their living environments.

"They may not get out to get sunlight exposure to their skin, which is a major source of activation of vitamin D," she said. "They may not have good nutrition, they may have other medical conditions or gastrointestinal problems, so they should talk to their doctor about their patient care."

Need for vitamin D

The body needs vitamin D. The vitamin's main job is to help the body absorb calcium from the intestines -- in fact, the body cannot absorb calcium unless vitamin D is present. The vitamin also plays a role in immune health, brain cell activity and how muscles function.

In the United States, 15 micrograms, or 600 international units (IU) of vitamin D a day, is recommended for adults up to 70 years old, according to the National Institutes of Health.

For adults older than 70, the dose rises to 20 micrograms or 800 IU each day. The American Academy of Pediatrics recently doubled the recommended amount for infants, children and adolescents to 10 micrograms or 400 IU per day.

Unlike water-soluble vitamins, which the body can easily eliminate, vitamin D and its cousins A, E and K, accumulate in the liver and fat cells of the body until they are needed. Consuming well over the daily recommended dose can build up to toxic levels.

A 2017 study found 3% of Americans took more than the tolerable upper limit of 4,000 IU daily for adults, thus putting themselves at risk for an overdose. About 18% took more than 1,000 IU daily.

Just after the first of the year, a British man began suffering from nausea, abdominal pain, diarrhea and repeated bouts of vomiting, along with cramping in the legs and ringing in the ears after a month of taking massive amounts of vitamin D three times a day. His vitamin D levels remained elevated for months, his doctor said.

If vitamin D supplements are being considered, daily levels of vitamin D obtained from food should be factored into the decision, experts caution. In addition to fortified foods, eggs, cheese, shiitake mushrooms, salmon, swordfish, tuna, rainbow trout and beef liver contain vitamin D, as does cod liver oil.

Anyone concerned about their vitamin D levels should have them evaluated by a doctor, experts say.

The-CNN-Wire

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