Bone Country "Remarkably enough, if dairy has any effect, both clinical and population evidence strongly implicate dairy in causing, rather than preventing, osteoporosis," declares PETA on its everything-bad-you-ever-wanted-to-know-about-milk website, milksucks.com. When it comes to anti-milk rhetoric, that's almost a moderate position.
Milk-dissenters argue that milk is a high protein food, replete with sulfur amino acids. These acids steal milk's neutralizing calcium – and grab even more from your bones. Then they abscond with it in the urine.
Actually, milk has a modest protein content (only slightly more than soy milk), and no more sulfur amino acids than nuts, seeds, or grains. Most importantly, the ratio of calcium to protein in milk is exceptionally high – 38 milligrams per gram – rivaled only by that calcium susperstar of the plant world, kale – 41.
"The calcium losses induced by milk protein are miniscule in comparison to the total calcium content of milk," write vegan dietitians Brenda Davis and Vesanto Melina in Becoming Vegan. Even after factoring in the 70 percent of milk calcium that passes through your gut unabsorbed, calcium balance studies suggest milk's protein claws back a not too greedy third of the calcium that doesn't.
The research?
In 2000, Roland Weinsier and Carlos Krumdieck published a comprehensive review on "Dairy Foods and Bone Health " in the American Journal of Clinical Nutrition. Over half of the roughly 50 studies they found reported no significant effect for or against milk or other dairy foods. Studies favourable to dairy outnumbered unfavourable ones 8 to 1, but most were low on the evidential food chain. But among "21 stronger-evidence studies. . . .the overall ratio of favorable to unfavorable effects . . . was 2.0." And when these were subdivided according to the age of the subjects, the ratio rose to 4.0 for people 30 years old and younger, but it sank to a milk-bubble-deflating 1.0 for everyone older.
As early as 1994, a U.S. National Institutes of Health consensus statement had determined that "intake and absorption account for only 25 percent of the variance in calcium balance [what the body keeps], whereas urinary loss accounts for approximately 50 percent. The typical American diet consists of high amounts of sodium and animal protein, both of which can significantly increase urinary calcium excretion."
Weinsier and Krumdieck's parting advice was that "age-related bone loss may be more attributable to excessive calcium loss than to inadequate calcium intake. Accordingly, greater attention needs to be given to eliminating the causes of calcium loss, which in turn should lower calcium requirements."
VERDICT: Milk almost certainly does a skeleton good, especially when you're young – but not nearly as good as the milk mustache people imply. Calcium is best thought of as a pivotal team player in a contest that includes eating less sodium and more potassium and vitamin K, avoiding excess protein (especially from meat, eggs, and fish) and vitamin A (beta-carotene is fine), getting plenty of sunshine or vitamin D, not smoking, and stimulating your bones regularly with physical activity.
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