Vitamin D may protect the pancreas from diabetes in people who are at high risk for the disease because their blood sugar levels are above normal.

            Researchers assigned 92 adults with predieabetes to take vitamin D, calcium, both, or a placebo. Then they measured how well beta cells in the pancreas secreted insulin.

            After four months, beta-cell function improved by 26 percent in the vitamin D takers and worsened by 14 percent in those who got no vitamin D. The worse your beta cells perform, the greater your odds of diabetes. Calcium had no impact on beta-cell function.

What to do: A large, long-term trial is now underway to see if vitamin D lowers the risk of diabetes. Until the results are in, shoot for 600 IU a day until age 70 and 800 IU a day after that.