Saturday, May 13, 2017

High Animal Protein Intake Reduces Frailty and Increases Survival In Japanese & Okinawan Elders

In a previous blog I discussed how natural selection has favored both strength and longevity in humans, and argued that evidence suggests that humans' increased intake of animal foods and restricted intake of plant foods during the Pleistocene probably played an important role in favoring the natural selection of longer life spans in humans compared to the other great apes.

In that blog I mentioned that we have evidence that animal protein is more effective than plant protein for maintaining muscle mass in humans, particularly people more than 65 years of age.

Yet it is sometimes claimed that Japanese live long and health because they eat little protein, especially animal protein.  This claim is a myth.

  Kobayashi et al report:
"Protein intake has been inversely associated with frailty. However, no study has examined the effect of the difference of protein sources (animal or plant) or the amino acid composing the protein on frailty. Therefore, we examined the association of protein and amino acid intakes with frailty among elderly Japanese women."
"Total protein intake was significantly inversely associated with frailty in elderly Japanese women. The association of total protein with frailty may be observed regardless of the source of protein and the amino acid composing the protein."
 In table 3 we find that women who ate the most animal protein, at least 54.8 g per day (fifth quintile), had the lowest absolute incidence of frailty, the lowest age-adjusted risk of frailty, and the second lowest multivariate adjusted odds risk of frailty, just slightly higher than the fourth quintile of the population, which consumed 45.6-54.8 g of animal protein daily.  The fifth quintile level of animal protein intake is equivalent to about 8 ounces of meat, fish or poultry; the fourth quintile range was 45.6-54.8 g per day, which is 6.5 to 8 ounces daily.

The positive association between plant protein and reduced frailty was less linear than the association between animal protein and reduced frailty.  Quintiles 3 and 5 for plant protein intake had lower odds ratios than quintiles 2 and 4. 

The table also shows a linear positive relationship between increased intake of branched chain amino acids (BCAAs) and sulphur amino acids and reduced frailty.  The best sources of BCAAs and sulphur amino acids are meat, chicken, fish, dairy products and eggs.  

The table also shows intake of at least 1.8 g/d of methionine was also associated with the lowest risks for frailty.  Animal proteins are the best sources of methionine.  This might call into question the idea that methionine restriction is a viable method for promotion of life span.  Such restriction may lead to frailty, which leads to premature disability and often death from falling.

This study resonates with the research by Shibata et al., which found that Okinawan centenarians eat more animal protein and fat and less carbohydrate than average Japanese (I have previously discussed Shibata et al. here.)

Since frailty impairs longevity, and animal protein reduces frailty, it follows that animal protein promotes longevity.  As it most likely did for our ancestors during the Pleistocene

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