NEW YORK (Reuters Health) - In certain Middle Eastern and other countries where conservative dress curtails exposure to sunlight, high levels of vitamin D supplementation may be needed to raise serum levels sufficiently in women, investigators report.

“When sunlight exposure -- the main source for vitamin D in humans -- is limited,” Dr. Hussein F. Saadi told Reuters Health, “much higher dietary intake of vitamin D is needed than currently recommended,” especially for women who are breast-feeding.

As reported in the June issue of the American Journal of Clinical Nutrition, Saadi and colleagues at the United Arab Emirates University, Al Ain, studied vitamin D levels in 90 women who were breastfeeding and 88 women who had never given birth. Many dressed to cover their whole bodies, including their hands and faces, while outside of their homes.

Only two of the women, one in each group, were not vitamin D deficient at study. All the women were randomly assigned to receive 2000 IU of vitamin D2 daily or 60,000 IU in one dose each month. The investigators note that vitamin D2 is the only high-dose calciferol available in the UAE.

Although both monthly and daily dosing significantly and safely increased vitamin D levels, only 21 of the 71 women (30 percent) who completed the 3-month study reached the recommended blood levels.

Vitamin D2 doses “as high as 2000 IU per day were marginally effective in ensuring adequate vitamin D status,” Saadi commented. He and his colleagues suggest that “if the more potent vitamin D3 preparation is not available, higher doses of vitamin D2 than currently studied may be needed.”

Dr. Saadi added, “When compliance or adherence with a daily regimen of vitamin D supplementation is an issue, monthly dosing appears to be a safe and effective alternative in ensuring adequate vitamin D status in subjects at risk for vitamin D deficiency.”

SOURCE: American Journal of Clinical Nutrition, June 2007.