In a commentary piece published this week in the Journal of the American Medical Association, Dr. Manson urges caution. She says that even though the public has become smitten with vitamin D, its growing popularity has led to mega-dosing that’s not backed by the current evidence. “More isn’t always better, more is sometimes worse,” Manson said in an interview. “We don’t yet have the answers, so we shouldn’t make assumptions.” But, she adds, in a couple of years, gold-standard evidence on whether higher doses of vitamin D are good for you should be out.