Protein / Soy Consumption
Some say that osteoporosis is due to excessive protein consumption
But there is hardly any correlation between average protein consumption by country, and osteoporosis incidence.
Some studies showed that protein intake positively correlated with bone-mineral density (1) and hip-fracture incidence. (2) But then again, the same is the case regarding calcium consumption. Since protein increase bone-formation rate (3), protein consumption must indeed accelerate ageing of the bones.
Other studies showed no correlation between BMD and protein intake (4), and that high dietary protein intake had no effect on Ca metabolism, bone composition or bone resorption. (5)
One study showed that there were not even correlations with extremely high protein intake (1.26 g / kg bodyweight) and calcium excretion rate. (6)
Several studies however, have found that animal protein strongly increases urine calcium. (7) And that in comparison with animal protein, soy protein decreases calcium excretion, as a result of the lower sulfur amino acid content of soy protein. (8)
Another study showed non-significant differences. (9)
And in another study, soy protein did not decrease the markers of bone turnover. (10)
Moreover, soy contains most phyto-estrogens (11), which are supposed to decrease bone turnover.
These phyto-estrogens however, are 'weak' estrogens, and can replace common (powerful) estrogens. (12)
Consuming soymilk for 3 months can already decrease estradiol level 27%, and lengthen menstruation cycle with 2 days. (13)Consuming phyto-estrogens can therefore even cause infertility (14).
And since estrogen is essential in inhibiting bone turnover, consuming phyto-estrogens can increase bone turnover. And phyto-estrogens do not inhibit bone-resorption more than natural estrogens do. (15)
Furthermore, the main phyto-estrogen in soy, genisteine, has adverse effects in higher doses. (16)
More importantly, genisteine enhances osteoporosis, for it increases activity of osteoblasts (17) /uptake of calcium into the bones. (18) For one part due to an increased intestinal calcium absorption. (19) Unlike the effects of estrogen, a soybean diet did not decrease bone-turnover in rats. (20)
In statistics, osteoporosis and protein consumption per country do not really correlate.
Protein consumption in Greece is highest, but incidence of hip fractures in Greece is not very high (21), and far lower than in Italy (22) , Switzerland (23), Sweden (24) etc.
Swiss protein consumption is even lower than Japanese protein consumption, but osteoporosis incidence in Switzerland is far higher. (25)
Kuwait protein consumption is quite low, but osteoporosis incidence is comparable to osteoporosis incidence in Italy and France. (26)
Protein consumption in gram / day; 1998
103 New Zealand
27 Dem. Rep. Congo
There is a correlation between protein consumption and osteoporosis, but it is not a strong one. Thus the influence of excessive calcium must be greater.
Soy on the other hand enhances osteoporosis.
Abstract of these sources can be found at the National Library of Medicine
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