Vitamin D: How Much Is Too Much?
A new study shows the number of U.S. adults who take high-dose vitamin D supplements increased significantly—from 0.3 percent to 18.2 percent—between 1999 and 2014 in the U.S. According to the study, which was published in JAMA, this may be concerning. Although vitamin D is important for bone health, extremely high doses may are linked to negative health effects, including kidney stones, bone fractures, and falls.
Sunlight is the main source of vitamin D; the body produces it when the sun’s UV rays are absorbed by the skin. It is also found in animal products—meat and dairy—and in mushrooms. The recommended dietary allowance of vitamin D is 600 IU (International Units) in people under age 70 and 800 IU in those over 70. The upper tolerable limit of vitamin D—the largest amount unlikely to cause harm—is 4,000 IU daily for people of all ages.
For the study, researchers examined data from the National Health and Nutrition Examination Survey involving about 40,000 people. In each survey from 1999 to 2006, fewer than 0.1 percent of adults reported taking 4,000 IU or more of vitamin D supplements a day, but in the 2013-2014 survey, 3.2 percent of adults reported taking at least that much.