Protein and Calcium
Jose Antonio, PhD, CSCS
You’ve heard the refrain of "if you eat more protein, you'll excrete more calcium" And so it goes, the protein wars are still being fought with lines drawn between the traditionalists who scoff at the possible benefits of eating more protein (than the RDA) and those in the athletic world and esoteric scientists who support the notion that more protein is needed for muscle-building, and to top it off, it just isn’t as bad for you as the doom and gloom crowd claims it to be.
Is it true that for every 50 gram increase in protein, you excrete an extra 60 mg of calcium. Recall that you need ~ 1,000-1,500 mg of calcium per day and a 200 lb individual probably consumes roughly 180 grams of protein per day. Thus, if you eat an extra chicken breast (~30 grams of protein), theoretically, you'd end up excreting 36 mg of calcium. This lost calcium represents less than 4% of your total calcium intake! Is this so difficult to replace? I don’t think so. All it takes is 1 ounce of 1% milk or eat 3/4s of a cup of raw broccoli to replace this!
Furthermore, there are a couple recent studies that will put an extra nail into the coffin concerning this archaic notion The most recent from Creighton University in Omaha Nebraska. In this study, 191 Roman Catholic nuns (yes, you read that right…nuns) aged 49 yrs were studied three times over a greater than 20 year period. In the words of the author, “the results reported here indicate that neither nutrient [protein or phosphorus] has a perceptible effect on calcium absorption.” Interesting. Now if you have a problem with a study using such an esoteric group of subjects, an earlier study 1 examined young healthy women. Women are typically chosen for these studies since calcium nutrition is more important as it relates to bone mineral density and osteoporosis; men typically do not have such a problem.
Nonetheless, this earlier study consisted of a two-week intervention period. Subjects ate a well-balanced diet followed by 5 days of the experimental diet (a low protein diet of 0.7 grams/kg or a high protein diet of 2.1 grams/kg). The high protein diet values are similar to what a “typical” bodybuilder might ingest.
And what did they find? The low protein group absorbed much less calcium than the high protein group. Intestinal calcium absorption was however normal in the high protein group.
Thus, at least with women, it is clear that jacking up your protein
intake isn’t the enemy of your bones as many have claimed. Of
course to keep it safe, women should supplement with calcium if they
eat insufficient quantities of dairy. But as far as the protein, high
intakes are perfectly fine!
Kerstetter JE, O'Brien KO, Insogna KL. Dietary protein affects
intestinal calcium absorption. American Journal of Clinical Nutrition.
68:859-865, 1998
Heaney RP. Dietary protein and phosphorus do not affect calcium absorption.
American Journal of Clinical Nutrition. 72:758-61, 2000.