The most vocal proponents of the protein-causes-bone-loss theory are those who promote vegetarian and vegan diets. These commentators rail not just against protein, but specifically animal protein. Animal protein, they assure is, is a major cause of the high rates of osteoporosis seen in Western countries.
If this were correct, we would expect to see higher bone densities in vegetarian and vegan individuals. In fact, the opposite is true. Studies repeatedly show either no difference or lowerbone densities in those who follow vegetarian diets.
A recent meta-analysis encompassing nine studies of 2749 subjects (1880 women and 869 men) found that, overall, bone mineral density was 4 percent lower in vegetarians than in omnivores at both the femoral neck and the lumbar spine. The effect was more pronounced in vegans, who totally avoid animal products. While the researchers concluded “the effect size is unlikely to result in a clinically important increase in fracture risk”, the results do not even begin to support the incessant and rather shrill claims by vegetarian/vegan activists that meat and animal protein are harmful to bones[2].
BLUF: The evidence does not support the thesis that "high protein" diets cause loss of bone minerals leading to osteoporosis, with the possible exception of those doing a very low carb, aka ketogenic diet, for a long time. This won't change what the vegans and vegetarians are saying, because the loud ones live in a world of fantasy anyway. However, I hope it will change what folks like Loren Cordain say, unless he can find some evidence to support his conjecture that we should eat vegetables and fruits to balance the net acid load of proteins (and cereal grains if you are into that sort of thing).
Aside from the lack of supporting evidence that "high" protein intakes present a risk to bone health through a high net acid load at the kidney, I have never thought it was smart to try and eat your way to a balanced acid load. How one could possibly sort out how much veg was enough to balance all the acid sources was always a mystery to me. For most diet inputs, if you don't have a way to measure the output, you are most likely just "whistling Dixie." The one exception to this policy I practice is to eat about a gram a day of DHA/EPA in fish oil, but when the DHA/EPA tests become reasonably priced, I'll use those to inform my dosages, much like I will use my next test of vitamin D levels to set my dosage for next winter.
Lastly, Colpo's post is a good example of how hard it is to get a good scientific outcome in human trials. Example: Eskimo's are reported to have accelerated bone demineralization, despite otherwise great health, very low rates of the diseases of the West, and an active lifestyle. It could be the high protein intake coupled with low plant intake that causes the bone loss, but it could also be low vitamin D from the long winters. Further, what if you live on the ketogenic side of the spectrum (IOW, very low carb, say 30g/day), but have a FEAST day once per week in which you way over consume? What if you are ketogenic but do a lot of strength work; will that overcompensation eliminate the bone loss? Ditto if you are a hard training vegan - will the body find a way to pull more of the available minerals into the bones in response to the demands of hard training? This is why application of even good studies, of which there are few, is problematic in real humans living in the variety of ways that we do, with multiple variables in diet, life style, age, gender, and other health factors like vitamin D levels, stress levels, sleep quantity and quality, etc etc etc.
So keep working on your N=1 experiment on yourself. And for that experiment, don't be overly fearful of your "high" protein intake.
No comments:
Post a Comment