From 1999 to 2000, just 0.3 percent of the population was taking 1,000 IU or more. But by 2013 to 2014, 18 percent of people were popping that amount daily.
The number of people taking super-high doses of D grew, too. In 2013 to 2014, three percent took 4,000 IU or more of vitamin D a day. Prior to 2005, less than 0.1 percent of people reported the same.
Important note: The tolerable upper limit—the maximum amount unlikely to cause negative health effects—for vitamin D is 4,000 IU a day, according to the National Institutes of Health. So three percent of the population was intentionally taking in an amount that put them over that safe benchmark.
While adequate levels of vitamin D are important, high dosages of vitamin D can lead to a bunch of health problems, the authors say. These include an increased risk of fractures, falls, and kidney stones. Other investigations have shown that high levels of vitamin D have been linked to prostate cancer, pancreatic cancer, and premature death of any cause.
Still, since low levels of vitamin D can cause health issues, it’s still one of the supplements you should actually take. Just make sure you’re not OD’ing on it—again, 4,000 IU is the daily max. (Need to fine-tune what you’re actually eating, too? Try The MetaShred Diet from Men’s Health—you’ll burn fat while preserving your hard-earned muscle.)
As for how much you should shoot for? There is some debate over that: The NIH recommends 600 IU, while the Endocrine Society suggests much higher levels of up to 2,000 IU daily.
Your best bet? Talk to your doctor. He or she can test your D levels, and come up with a supplementation level based off that.