Doctor recommended. Proven effective in more clinical studies. Proven absorption. Each tablet provides 250 mg of elemental calcium. Here are some very good reasons to choose Os-Cal: It is recommended by doctors; it has been clinically proven effective to help maintain bone mass in many more studies than any other brand; it is made from oyster shell, a 100% natural, organic source of calcium; it contains the most concentrated form of calcium you can buy; it has Vitamin D, proven to enhance calcium absorption. Every batch of Os-Cal is quality tested to meet USP dissolution standards. Osteoporosis...What you should know. What you can do. Osteoporosis affects middle-aged and older persons, especially Caucasian and Asian women, and those whose families tend to have fragile bones in later years. A lifetime of regular exercise and eating a healthful diet that includes enough calcium, especially during teen and early adult years, builds and maintains good bone health and may reduce risk of osteoporosis in later life. Older women can benefit from greater calcium intake, too. Adequate calcium intake is important, but daily intakes above 2000 mg are not likely to provide any additional benefit. Lactose free; no sugar; sodium free.