Three percent of Americans take way more than the recommended dosage of Vitamin D supplements a day—and new research suggests it’s pointless, and maybe even counter-productive. A study published Tuesday in the Journal of the American Medical Association examined people taking three different doses of the vitamin: 400 IU, 4,000 IU, and 10,000 IU. The goal was to see if the megadoses would improve bone mineral density and bone strength. What they found was bone mineral density was actually worse at the higher dosages, and there was no difference in bone strength at any dose. More research must be done before anyone can say high-dose D depletes bone mineral density, but the results indicate there’s no reason to go beyond the recommended dose for bone health.