Researchers find that getting too little vitamin D may increase your risk of multiple cancers, including breast, colon, prostate, ovarian, and stomach, as well as osteoporosis, diabetes, multiple sclerosis, and high blood pressure. Exposure to UVB rays found in natural and artificial sunlight. About 15 minutes a day ought to do it. Avoid overexposure, of course. That can increase your risk for cancers of the skin. You can also get vitamin D in your calcium supplement if you choose a supplement that contains both "http://www.rd.com/health/conditions/31-simple-ways-to-prevent-cancer/2/">