Calcium is continuously lost through body waste and sweat, and is replaced with calcium from the bones. As a process of normal tissue growth, the body constantly breaks down bone material and rebuilds it, using calcium from foods for replacement Keeping bones strong depends more on preventing calcium loss than on increasing calcium intake. In nations with high rates of osteoporosis, protein intake is generally more than twice the U.S. Recommended Daily Allowance. Diets that are high in protein, especially animal protein, cause calcium to be lost through the urine. Meats are high in a particular kind of protein building block, called sulfur-containing amino acids, that cause increased calcium loss.
Studies show that vegetarians have less than half the amount of osteoporosis that meat eaters have.
Caffeine and sodium also increase the rate of calcium loss through urine. Alcohol inhibits calcium absorption and may also be toxic to bone. We can benefit from boron, found in fruits, vegetables, and beans, since it appears to help stop the loss of calcium. Vitamin D, copper, zinc, and weight training exercise also may increase bone mass and help to prevent osteoporosis. The need for calcium varies at different ages.