500 +D. No. 1 Doctor recommended. Proven effective in more clinicals. Gluten Free. Reasons to choose Os-Cal: No. 1 Doctor recommended. Proven effective in clinical trials to help maintain strong, healthy bones. Helps reduce the risk of osteoporosis. Highly absorbable calcium. Meets USP dissolution standards. This Os-Cal 500 +D has no sugar, lactose, carbohydrates or sodium. This Os-Cal 500+D has 0 calories; one Viactiv has 20 calories. This Os-Cal 500 +D has 500 mg of elemental calcium. Don"t take chances - Take Os-Cal. Osteoporosis - Regular exercise and a healthy diet with enough calcium helps teen, middle-aged and older women and men maintain good bone health. While Caucasian and Asian women are at greatest risk, all middle-aged women, those with a family history of the disease, and older men and women are at risk for developing osteoporosis. Adequate calcium intake is important, but daily intakes above 200 mg are not likely to provide any additional benefit. Active, healthy lives depend on strong, healthy bones! Os-Cal, helps keep bones strong. The Os-Cal brand of calcium supplements is the No. 1 Dr. recommended among leading calcium supplement brands. Made in the USA.