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is animal protein OK for bones?
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jc3737 posted:
Nutr. 2003 Mar;133(3):862S-865S.Dietary animal and plant protein and human bone health: a whole foods approach.Massey LK .SourceFood Science and Human Nutrition, Washington State University Spokane, 99210, USA. massey@wsu.edu
AbstractUrinary calcium excretion is strongly related to net renal acid excretion. The catabolism of dietary protein generates ammonium ion and sulfates from sulfur-containing amino acids. Bone citrate and carbonate are mobilized to neutralize these acids, so urinary calcium increases when dietary protein increases. Common plant proteins such as soy, corn, wheat and rice have similar total S per g of protein as eggs, milk and muscle from meat, poultry and fish. Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium. The effects of a protein on urinary calcium and bone metabolism are modified by other nutrients found in that protein food source. For example, the high amount of calcium in milk compensates for urinary calcium losses generated by milk protein. Similarly, the high potassium levels of plant protein foods, such as legumes and grains, will decrease urinary calcium. The hypocalciuric effect of the high phosphate associated with the amino acids of meat at least partially offsets the hypercalciuric effect of the protein. Other food and dietary constituents such as vitamin D, isoflavones in soy, caffeine and added salt also have effects on bone health. Many of these other components are considered in the potential renal acid load of a food or diet, which predicts its effect on urinary acid and thus calcium. "Excess" dietary protein from either animal or plant proteins may be detrimental to bone health, but its effect will be modified by other nutrients in the food and total diet.
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heretk responded:
Not only the study does conclude that consuming animal and plant protein is OK. The data of most of the 6 studies reviewed in this compilation, show that consuming more protein (but only up to the total limit of 95g) increases BMD (bone mass density) and decreases fractures! Only one out of six studies favors plant proteins over animal!

Look at table 1

http://jn.nutrition.org/content/133/3/862S/T1.expansion.html

Study #1: "191ap "191BMD "191pp "193BMD
Animal protein up = BMD up
Plant protein up = BMD down

Study #2: "191ap "193Fx "191p "193Fx
Animal protein up = Fractures down
Total protein up = Fractures down

Study #3: "191ap "193Fx "191p "191BMD
Animal protein up = Fractures down
Total protein up = BMD up

Study #4: "191p "191BMD (protein source irrelevant)
Total protein up = BMD up

Study #5: "191ap:pp "191hip Fx
Ratio of animal to plant protein up = hip fractures up

Study #6: "191p "191Fx (> 95g p)
Total protein up (above 95g) = Fractures up
 
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heretk replied to heretk's response:
Note, in the original text:


symbol "191 = UP ARROW


symbol "193 = DOWN ARROW


ap = animal protein
pp = plant protein


p = total protein


BMD = bone mass density
Fx = fractures

 
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jc3737 replied to heretk's response:
I wonder why 95g would be the tipping point?
 
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engineerguy replied to heretk's response:
Hi Heretic,

Re: "Not only the study does conclude that consuming animal and plant protein is OK. The data of most of the 6 studies reviewed in this compilation, show that consuming more protein (but only up to the total limit of 95g) increases BMD (bone mass density) and decreases fractures! Only one out of six studies favors plant proteins over animal!"

No, the studies do not conclude that at all.

"Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium."

That was purified protein, used in the studies. As the abstract states, the results from experimentally consuming purified protein is only part of the answer, since the whole food has a different effect than the purified protein.

Can we conclude from this information that consuming animal (or plant) protein is OK? No, because the study is only about purified protein, which nobody eats. We can bear in mind that, as societies get richer, they consume much more meat (and make many other changes) and their bone fracture rate increases dramatically. If animal protein is beneficial for the bones, as you assert, the benefit is woefully inadequate to overcome the overall deficit experienced from leaving our more natural condition, with a mostly whole plant based diet, as well as more exercise, less sodium, etc etc.

Best regards, EngineerGuy
 
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heretk replied to engineerguy's response:
EG,

Yes if they used purified protein then this would be a serious flaw in the study. Protein consumption has not increased dramatically, neither did fat (total) nor carbohydrates.

However, sugar has increased dramatically and the type of fat is very different.

There are also other diet related factors that may indirectly promote osteoporosis. For example auto-immune diseases.

You have to be careful about sodium. Salt is essential on the high carbohydrate diet - you cannot assume that the less the better. Native people would pay a fortune to buy salt, otherwise they suffered.
 
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jc3737 replied to heretk's response:
Some studies confirm that the minor amount of sodium in vegetables is plenty and that such low amounts are a health advantage. And yet some more recent studies conclude that higher levels of sodium are healthy.

I have followed the research on this for years and the signals are moving from massive research in support for low sodium to a more mixed picture recently.

I have no idea how it will eventually settle out but I know that i am personally not able to tolerate sodium at all.


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