Calcium
The majority of people in the U.S. do not consume adequate quantities of calcium, so would likely benefit from supplementation. Adequate calcium intake seems to increase peak BMD. In post-menopausal women calcium supplementation reduces the expected loss in BMD and produces a non-statistically significant reduction in vertebral fractures. (7)
Most calcium supplements are in the form of calcium carbonate which is best absorbed from an acidic environment, so are best taken with food. Prolonged use of proton pump inhibitors (omeprazole, pantoprazole, etc.) has been correlated with increased risk of osteoporotic fractures (8), probably through decreased absorption of calcium from carbonate form. Calcium citrate is absorbed without effect of gastric pH, though supplements are more expensive.
Calcium Content of Foods
Dairy
Yogurt: 1 cup, 415mg
Milk: 1 cup, 300mg
Cheese (Swiss): 1oz., 272mg
Vegetables
Tofu: 1/2 cup, 120-350mg
Kale (Cooked): 1/2 cup, 103mg
Navy beans: 1/2 cup, 62mg
Broccoli: 1/2 cup, 47mg
Other
Sardines (canned): 8, 350mg
Calcium Content of Selected Supplements (Elemental)
Caltrate 600: 600mg (carbonate)
Caltrate 600 + D: 600mg (carbonate), 200 IU vit D
Oscal 500: 500mg (carbonate)
Oscal Ultra: 600mg (carbonate), 200 IU vit D
Tums: 200mg (carbonate)
Tums EX: 300mg (carbonate)
Tums Ultra: 400mg (carbonate)
Citracal 250 + D: 250mg (citrate), 200 IU vit D
Calcium Gummy Bears: 200mg (phosphate)
Viactiv plus D + K: 500mg (carbonate), 200 IU vit D
Centrum Silver: 162mg (carbonate), 400 IU vit D