MotherJones MA95: Eat a Steak, Break a Bone
News: The real culprit behind the rise in osteoporosis in America may be too much animal protein.
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Conventional wisdom on osteoporosis is that women aren't getting enough calcium and exercise. While weight-bearing exercise certainly helps prevent osteoporosis, the value of increased calcium intake is surprisingly controversial. The National Institutes of Health declared last June that half of American adults aren't getting enough calcium (defined as 1,000-1,500 mg. a day, or 3-5 glasses of milk). Yet, in the United States, where consumption of dairy foods ranks among the highest per capita in the world, women suffer one of the world's highest rates of osteoporosis. Some studies have shown a modest increase in bone density with increased calcium consumption, but many have not, prompting the prestigious journal, Science, to note that a "large body of evidence indicates no relationship between calcium intake and bone density."
The dairy industry continues to recommend "more calcium." The problem is that its products, though high in calcium, are also high in animal protein, which "looks more and more like a major cause of osteoporosis," says Dr. Neal Barnard of the Physicians Committee for Responsible Medicine.
Protein is composed of amino acids, which, when digested, increase the blood's acidity. In reaction, the body releases substances that neutralize acid into the blood; one that is readily available is calcium stored in the bones. "Many studies show that as protein consumption increases, so does calcium excretion in the urine," says Dr. David Perlmutter, a neurologist/psychiatrist in Naples, Fla.
The largest source of protein in the American diet is meat. Like dairy, it pumps amino acids into the blood; they in turn suck calcium out of the bones. Unlike dairy, however, meats don't contain much calcium to replace what they remove. A recent University of Florida study involving 150 vegetarian and omnivorous women, aged 45 to 65, found that, compared with omnivores, vegetarians had greater bone density and showed less calcium excretion in their urine.
Naturally, the meat and dairy industries don't want you to know that animal products appear to play a major role in osteoporosis, which afflicts as many as 25 million Americans and costs an estimated $10 billion a year. They also don't want you to know that a good vegetarian diet (which should supply all the protein and calcium you need) may be the key to prevention. But now you know.
