Protein and age

[mccoy]

This is one of the latest citations from Al Pater's thread:

 

Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men: A Randomized Clinical Trial.
Bhasin S, Apovian CM, Travison TG, Pencina K, Moore LL, Huang G, Campbell WW, Li Z, Howland AS, Chen R, Knapp PE, Singer MR, Shah M, Secinaro K, Eder RV, Hally K, Schram H, Bearup R, Beleva YM, McCarthy AC, Woodbury E, McKinnon J, Fleck G, Storer TW, Basaria S.
JAMA Intern Med. 2018 Apr 1;178(4):530-541. doi: 10.1001/jamainternmed.2018.0008.
PMID: 29532075

 

 

It's interesting to observe that, in men with mean/Sd age 73/5.8, even with the administration of testosterone (which boosts IGF-1 concentration), an increase from the 0.8 g/kg/d to 1.3 g/kg/d did not have effect on LBM and strenght.

 

Obviously, that's because of the lack of physical exercise.

 

An interpretation of the study from the POW of cellular signaling may be that, even in the presence of the amminoacid+IGF-1 signal, the contribute of the mechanoreceptors signal (physical stress) is absolutely essential to obtain an upregulation of mTOR in skeletal muscle, at least in those aged 70+.

[Jonnywallter]

I've done some more research. One of the studies he bases his claim that high protein diets are unhealthy on is this one: 'Dietary preferences and diseases of age' Bras & Ross. Nature, 1974.

It shows that rats on a 22% protein diet had a 4 times higher chance of getting heart disease than rats on a 10% protein diet. Rats on a 51% diet did worse. They also had a higher chance on kidney and prostate problems.

I wonder what this says for human beings. 

If high protein is really this unhealthy I would expect it has been investigated in large studies with humans.

[mccoy]

Jonnywalter, the most authoritative reference about protein, aging and longevity right now seems to be Valter Longo's contention (based on an epidemiological research) that after 65-70 years human beings need more than 0.8 g/kg/d protein (the official RDA) to counteract sarcopenia, a trend toward increasing loss of musculoskeletal tissue. This on the average of course, in his book he makes a qualitative allowance for individual variation.

Longo also says that the protein surplus should be higher in animal protein, to boost systemic IGF-1, which hopefully will overamplify local IGF-1 in muscles.

 

In his stemtalk interview though, he also says that we might avoid increasing protein after this age if we exercise every day, stimulating the mechanoreceptors (this bypasses the insulin/IGF-1 PI3K-Akt cascade to activate mTOR). He insists on daily resistance exercise, albeit we know that muscles do not recover after one day of real weight ligfting, unless it's very light weights.

 

Of course the leucine signal must be there, otherwise no way mTOR si going to be phosphorylated. and this means, according to Longo, to arrange a post-workout meal with 30 g protein. 

 

My ongoing experiment is that a surplus of protein is useless if an adequate mechanoreceptors stymulus is not present. This agrees perfectly with the functional role of skeletal muscles and the bodily economy. If we use muscles to lift and move heavy weights, provided mTOR is activated, muscle protein synthesis will occur and will be proportional to the need (the usual average loading).

 

There are so many other factors, the  androgens baseline, the myostatin, soem enzymes and more, the bodybuilders know that all, they are the really practical experts on muscle growth, science only gave a mechanistic explanation to their empirical observations.

[Todd Allen]

Mccoy,  I think you are right, exercise is a needed stimulus.  There are countless studies showing the importance of exercise.  Exercise also boosts insulin sensitivity.  I suspect that much of the need for the increasing amount of protein to stimulate muscle protein synthesis with advancing age is due to the commonly seen loss of insulin sensitivity with advancing age.  My guess is the change in insulin sensitivity is probably an indirect benefit of exercise's positive impacts on muscle mitochondria.