Low Protein Intake May Also Harm Bones

by Michael Greger, M.D.

We've known for over 80 years that increased protein intake leads to increased calcium loss in the urine[6] Especially, it seems, from acid-forming proteins found in some animal products. So one might guess that vegetarians would need less calcium because they lose less in their urine. Unfortunately, this is a myth[7].

First of all, those acid forming proteins aren't found in all animal products and are also found in high amounts in some plant foods too, like grains. Research suggests that vegetarians consume just as much of those sulfur-containing acid-forming proteins as meat-eaters[8]. And just last month a study reported new data that showed that too litle protein may also not be good for your bones[9].

Although on average most Americans exceed the RDA for protein by about 40%, one out of every five men in the U.S. and one in three women don't even reach the RDA for protein[10]. And these were meat-eaters. So everyone has to ensure they're getting enough protein in their diet (while not getting too much).

We should be shooting for about 0.9 grams per kilogram of healthy body weight. For us metric illiterate Americans, that means you basically multiply your "ideal" weight in pounds by 0.4. In other words, multiply by 4 and divide by ten. So for me, ideally for my height I should weigh about 150 pounds, so 150 times 4 is... 600, divided by ten is... 60. So I should eat about 60 g of protein a day.

If you don't know what your "ideal" body weight is, and you're of average build, you can base your protein requirements on height. You take your height-in-inches squared and multiply by 0.012. OK, so I'm 5'11", so that's 71 inches. So 71 x 71 x.012 = 60.

You can look at my Plant-Based Sources for Key Nutrients handout on my website for a list of some plant protein superstars. So yes, it's easy to get enough protein on a veg diet with foods like beans, but to do so we actually have to eat them! We should all be eating beans every day. (Let me guess--the mailbag question next month will be about flatulence, how much do you want to bet? :).

REFERENCES

[6] J. Biol. Chem 1920;44:21?e7.
[7] http://www.llu.edu/llu/vegetarian/myths.htm
[8] J Am Coll Nutr 1991;10:308-314.
[9] Am J Clin Nutr 78(2003):584s.
[10] US Department of Agriculture, Agricultural Research Service. 2000. Continuing Survey of Food Intake by Individuals CSFII 1994?e96.