foot x rayResearch appearing in the Journal of Bone and Mineral Research (2008 May;23[5]:741-9) found that supplementation with vitamin D and calcium may reduce the instance of stress fractures. Researchers gave 2,000 mg. of calcium and 800 IU of vitamin D, or a placebo to a random sampling of over 5,000 female Navy recruits during the eight weeks of basic training. During training, 309 of the recruits developed stress fractures. Those who received the supplementation had a 20% lower incidence of stress fractures than the placebo group.