Q. Does including calcium improve absorption of Vitamin D? I eat sardines two to three times a week, and wonder if including a calcium supplement at the same time would be a wise move? (Im middle-aged and averagely active with no known deficiencies in either vitamin.)

A. Its true-and very important-that vitamin D is key to the bodys absorption of calcium, which is why adequate vitamin D intake is crucial to protecting your bones. But is the reverse also true? Does calcium help improve the absorption of vitamin D from foods such as sardines? (One 3.75-ounce can of sardines with bones contains 178 IU of vitamin D, about the same as found in a cup and a half of milk.)

For the answer, we turned to Tufts vitamin D expert Bess Dawson-Hughes, MD, director of the Bone Metabolism Laboratory at the USDAs Human Nutrition Research Center on Aging. She replied: We studied this years ago and found that vitamin D absorption is not affected by the calcium intake level.