The IOM recommends 600 International Units (IU) per day.

Vitamin D deficiency is common worldwide and has been associated with heart disease, immunological diseases, infections and cancer. Studies have linked vitamin D deficiency to a higher risk of hypertension, but evidence for the beneficial effect of vitamin D supplementation on blood pressure outcomes is inconclusive.

“Our study found vitamin D supplementation may decrease blood pressure in specific subgroups such older people, people with obesity and possibly those with low vitamin D levels,” said Ghada El-Hajj Fuleihan, M.D., M.P.H., F.R.C.P., of the American University of Beirut Medical Center in Beirut, Lebanon. “High vitamin D doses compared to the IOM’s recommended daily dose did not provide additional health benefits.”

The researchers studied 221 older people with obesity taking vitamin D supplements at either 600 IU/day or 3,750 IU/day over the course of a year and found supplementation decreased their blood pressure.

The researchers compared the two groups and found higher doses of vitamin D did not provide additional health benefits. They determined people with obesity and those with low vitamin D levels benefited the most.

Other study authors include Maya Rahme of the American University of Beirut Medical Center; Laila Al-Shaar of Pennsylvania State University in University Park, Pa.; and Hani Tamim of the American University of Beirut Medical Center and the Alfaisal University in Riyadh, Saudi Arabia.

This research received financial support from the Office of Dietary Supplements, the University Research Board of the American University of Beirut, the Council for Research of the Saint Joseph University of Beirut, the National Council for Scientific Research, the Mayo Clinic, and the Odense University Hospital.