Does (Animal) Protein Leach Calcium from Bones?
[Thank you for all the responses to my request for information on increasing bone mineral density! I received a lot of responses and am still working my way through them.]
Because I’m planning to write a more reader-friendly version of VeganHealth.org’s Bones, Vitamin D, and Calcium, I decided to check in on the research on protein and bone health. In so doing, I found a 2012 review from a group of researchers in France who declared having no conflicts of interest (1).
There has been an enormous amount of research on protein and bone health and their review had almost 4 pages of references. I will hit the highlights of what they found:
– Many clinical trials show that adding purified proteins to the diet increases calcium excretion through the urine.
– Phosphorus, in which meat and dairy are rich, counteracts the increase of calcium in the urine between 40 and 65%.
– Findings that older people in Western countries have higher hip fracture rates are confounded by the fact that people in Western countries live longer, protein intakes were not estimated for individuals, and there are ethnic differences in bone structure and lifestyles.
– High protein diets increase acid excretion in the urine, but this can be handled by the body’s acid buffer system without the need for calcium.
– Studies measuring whole-body calcium balance (as distinct from excretion) in relation to high protein diets have been mixed, but this might partly be due to the difficulty in measuring calcium balance and because high protein diets might reduce calcium balance when calcium intakes are particularly low.
– In low-calcium, but not high-calcium diets, higher protein intakes probably increase calcium absorption from the digestive tract causing an increase in calcium excretion in the urine.
– Fruits and vegetables are beneficial to bone health, probably due to their high potassium and magnesium content. This could cause confounding in protein studies because diets high in protein are often low in fruits and vegetables.
– As I describe in my post Protein Intake and Bone Health, Darling et al. (2009) found that a large majority of the cross-sectional surveys and cohort studies have reported either no association or a beneficial association between protein and bone mineral density.
– There is some evidence that a beneficial effect of protein on bones is only seen when calcium intake and vitamin D status is adequate.
– Maintenance of adequate bone strength and density with aging is dependent on adequate muscle mass which is dependent on adequate intake of protein.
– An increase in IGF-1 is most likely the mechanism for increased bone health with higher protein intakes.
They conclude, “Although HP [high protein] diets induce an increase in net acid and urinary calcium excretion, they do not seem to be linked to impaired calcium balance and no clinical data support the hypothesis of a detrimental effect of HP diet on bone health, except in the context of inadequate calcium supply.”
Reference
1. Calvez J, Poupin N, Chesneau C, Lassale C, Tomé D. Protein intake, calcium balance and health consequences. Eur J Clin Nutr. 2012 Mar;66(3):281-95. | link
February 26th, 2013 at 5:45 am
Do you know what would explain the high incidence of osteoporosis in the U.S. population? Thank You.
February 26th, 2013 at 8:57 am
Louisa,
Ginny Messina addresses that there:
http://www.theveganrd.com/2010/05/vegan-calcium-needs-working-through-the-myths.html
February 26th, 2013 at 6:55 am
Thanks for this, Jack. I know it is easiest to go with vegan dogma (“meat evil! protein causes osteoporosis!”), but I think you are right that honesty is the best policy.
This goes back to another point you make, that new people trying low-protein vegan meals find them unsatisfying. In this sense, it would seem the vegan anti-protein mythology hurts animals.
February 26th, 2013 at 9:02 am
Bertrand,
First, let me say that I’m honored to have a ghost of your stature complimenting my writings.
I should add that I don’t necessarily think that all new people trying low-protein (and low-fat) vegan meals will find them unsatisfying, but it is a good bet that many or most will.
February 26th, 2013 at 6:52 pm
Question: many of these bullet points specify “high protein” without specifying the kind of protein. Is there any information on the relative merit of vegetarian vs. animal protein? In particular, is it possible that there is some benefit to having “protein” that is masking detriments of animal protein, while those same benefits (without the detriments) would be available in a vegetarian diet?
Thanks
Daniel.
February 26th, 2013 at 7:35 pm
Animal protein tends to come paired with phosphorus which is good for calcium balance while plant protein tends to be paired more often with potassium, vitamin K, and magnesium which are also good. The long term studies in the link I included to Darling et al. did some analysis of plant vs. animal protein.
September 9th, 2013 at 10:19 am
This needs to be compared with raw fruits and vegetables as they differ in protein than cooked proteins from vegan diets which lack.
September 9th, 2013 at 5:27 pm
Dave,
I have no idea what you mean. Are you saying that since animal protein appears to be good for bones, then raw vegan protein is even better?