When it comes to vitamin D supplements, it’s possible that Americans may be getting too much of a good thing, new research suggests.
In 2014, just over 3% of U.S. adults took more than 4,000 IU of the vitamin daily, exceeding the upper limits of what is considered safe, the researchers said. In 2007-2008, only 0.2% did that.
For perspective, the recommended daily amount of vitamin D is only 600 IU for adults aged 70 and younger. For those over 70, the recommendation is 800 IU a day.
“More may not always be better with vitamin D,” said study author Mary Rooney, a doctoral student at the University of Minnesota in Minneapolis.
“There’s not much research on longer-term health outcomes on high-dose supplements,” she said. But studies have hinted at potential harm, such as excess calcium in the blood, which can cause deposits in blood vessels, Rooney and her colleagues said.
One reason people may be taking so much extra vitamin D is concern about getting too little of the vitamin. The vitamin is crucial for good bone health, according to the researchers.
Vitamin D is known as the sunshine vitamin because the body makes it naturally when exposed to sun. It’s also found in fortified foods such as milk, and naturally in fatty fish such as salmon, Rooney said.
Heller said that appropriate vitamin D levels have been liked to lower risks of certain cancers, early death, depression in adolescents, type 2 diabetes, and improved heart health and immune system regulations.
But she noted that vitamin D deficiencies are common worldwide, and said many people may need to take vitamin D supplements to get sufficient amounts.
“Our bodies are designed to get the bulk of our vitamin D from the sun,” said Heller, who wasn’t involved with the study. “However, the use of sunscreen – a necessary and important step in the prevention of skin cancers – indoor jobs, less outdoor activities, aging and obesity are just some of the reasons so many of us have low levels of vitamin D.
But Rooney and her colleagues are concerned that the pendulum may have swung too far in the other direction, and that some people may be taking too much vitamin D.
The study was published as a research letter in the June 20 issue of the Journal of the American Medical Association.
High dosage vitamin D supplementation stems from a study several years ago that used 50,000 IU of vitamin D taken once a week. Using “evidenced based medicine” physicians today are still commonly prescribing this massive overdose to patients.
The high, once-a-week dose was given to verify compliance. Test subjects visited the clinic on a weekly basis to take the supplement.
Additionally, liver toxicity statistics were withheld from publication.
The Bottom Line:
Vitamin D deficiency is all too common. I routinely test my patients for their vitamin D levels. However, I recommend 4,000 IU daily as the maximum therapeutic dosage. I also suggest you go outside without sun protection in the early morning or late afternoon and get your vitamin D naturally.
Source: June 20, 2017 National Institutes of Health