Are Americans getting enough calcium? I've heard that health officials here may recommend more calcium than is necessary. How much do people really need?
Calcium is an essential nutrient, but the optimal intake is an unsettled issue. For adults over 50, the definition of adequate intake in the United States is 1,200 milligrams per day; in the United Kingdom, this is 700 milligrams per day; and the World Health Organization, looking at the same data, concluded that 500 milligrams per day is adequate. The primary justification for high consumption of calcium has been prevention of osteoporosis and fractures, and much of the disagreement is due to the use in the United States of short-term studies of calcium deposition in bones to set the value for adequate calcium intake. Long-term studies do not support benefits of high intake of calcium or milk in preventing fracture risk. The WHO conclusions were influenced by the observation that most adults worldwide consume little or no dairy products, have calcium intakes below 500 milligrams per day, and tend to have lower rates of fractures than we do in America and Europe, where calcium and milk intake are relatively high.
The issue of optimal calcium intake is complicated by evidence that high intakes—the amounts in about three glasses of milk per day—probably increase risks of fatal prostate cancer and, when taken as supplements with vitamin D, will increase risks of kidney stones. Given all the evidence, the British definition of adequate intake of 700 mg per day for adults seems to be reasonable, and this can be obtained with about one glass of milk per day in addition to an otherwise good diet. Other factors, especially adequate vitamin D and regular physical activity, are far more important than high calcium intake in preventing fractures. For growing children, intakes should be higher because of the need to accumulate calcium in growing bones, but the exact number is still not clear.
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