Vitamin D is linked to a number of health benefits, including strengthening bones and teeth and a lower risk of developing health conditions like diabetes and certain cancers. It is also is thought to have protective benefits against cognitive decline in older adults.
But a new study suggests when it comes to vitamin D, too much can be a bad thing.
According to the research, published in JAMA Internal Medicine, higher monthly doses of vitamin D offer no benefits when it comes to lower extremity functioning and muscle strength in adults over the age of 70. What's more, higher doses also led to an increased risk of falling in these seniors.
Falls are the leading cause of injury among older adults and can set off a downward spiral of health problems and loss of independence.
Dr. Heike A. Bischoff-Ferrari of the University Hospital Zurich in Switzerland and her team conducted a one-year, randomized clinical trial that included 200 men and women aged 70 or older who had suffered a prior fall. Almost 60 percent of them were vitamin D deficient before the start of the study.
The researchers divided the participants into three groups: one third received 24,000 IU (international units) of vitamin D3 per month -- the current recommended daily allowance by the Institute of Medicine (IOM); another third received a higher dose, 60,000 IU of vitamin D3; and the third group received 24,000 IU of vitamin D3 plus calcifediol, a broken-down version of vitamin D more readily available to the muscles and bone.
After following up after six and 12 months, the researchers found that just over 60 percent of the participants experienced falls during the one-year period. But there was a big difference between the groups: those in the low-dose group were significantly less likely to fall.
Those in the high-dose 60,000 IU group, as well as in the group that got 24,000 IU of vitamin D plus calcifediol, had higher rates of participants who fell -- 66.9 percent and 66.1 percent, respectively -- than the low-dose group, which had a fall rate of 47.9 percent.
The higher dose or combination of vitamin D plus calcifediol "conferred no benefit on the prevention of functional decline and increased falls in seniors 70 years and older with a prior fall event," the study authors wrote. "Therefore, high monthly doses of vitamin D or a combination of calcifediol may not be warranted in seniors with a prior fall because of a potentially deleterious effect on falls."
The authors noted several limitations to the study, including that findings may not apply to younger seniors or to individuals with more limited cognitive or functional abilities. There was also no placebo group. "Therefore, our trial supports low-dose over high-dose vitamin D supplementation but cannot establish a benefit of low dose over placebo," the authors wrote.
In an accompanying editorial, another group of researchers pointed out that in fact, no randomized clinical trials -- considered the gold standard of research -- have definitively shown the benefits of vitamin D supplements in preventing falls and fractures.
Until that happens, experts suggest that it is prudent to follow recommendations from IOM that people 70 years or older have a total daily intake of 800 IU of vitamin D, preferably from a balanced diet, or if needed, with the help of supplements.