Experts debate the proper dose of vitamin D at HSPH Forum
A panel of experts gathered on March 25 to debate how much vitamin D is enough and how much is too much. The webcast event was the latest sponsored by The Forum at Harvard School of Public Health as part of the Andelot Series on Current Science Controversies.
The Institute of Medicine (IOM), in a long-awaited report released in November 2010, recommended increasing the daily vitamin D intake for children and adults in the U.S. to 600 international units (IU) per day for people ages 1 to 70, and 800 IU for people over age 70. It also stated that most are already getting what they need.
Critics, including panelists Walter C. Willett, chair of the Department of Nutrition at HSPH and Bess Dawson-Hughes , a bone health specialist at Tufts University, argue that the new guidelines are overly conservative about the recommended intake and fail to acknowledge vitamin D’s health benefits beyond strengthening bones.
Panelists JoAnn Manson of HSPH and Patsy Brannon, both IOM committee members, maintained that there was no conclusive evidence that higher doses of vitamin D were beneficial, and that they may be harmful to some people. Brannon, a Cornell University nutrition professor, joined the conversation on a video uplink.
Vitamin D is found in foods including fatty fish and fortified grains, and also is absorbed through exposure to the sun. Manson recommended taking a supplement rather than increasing exposure to the sun due to increased risk of skin cancer.
Brannon stated that testing for vitamin D levels is only recommended for those at high risk, including people who are obese or dark-skinned, or have osteoporosis, seizure disorders, or problems absorbing vitamin D.
All of the panelists agreed that the IOM report was a public health recommendation for a broad population and that individual decisions about the proper dose of vitamin D should be made at the doctor-patient level.