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Personally, I don’t calculate protein intake. I just follow a purely whole foods plant based diet and my protein intake falls to where it needs to be while my biomarkers of health are favourable and are consistent with what is observed in the CR research. 

My wife on the other hand practices a version of CR that is fairly calorie restricted but with a higher percentage (and total) amount of protein than I. She consumes a mix of animal and plant based protein. I maintain a BMI of about 20.7 on my regime of not aiming for any particular protein intake. My intake is probably around 80g daily and hers is around 120g daily. I believe that too much protein is probably harmful to longevity due to its role in a number of signalling pathways. 

Dr. Michael Greger has a new book coming out soon (How Not To Age) and he has indicated that a high protein intake is usually associated with poor longevity. 

Edited by drewab
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The issue of the optimal amount of protein for longevity is highly controversial. What seems to be reasonable is that after 60 probably it's better to increase the quantity of protein (best if we think in terms of essential amino acids) to contrast the natural trend toward sarcopenia (and possibly osteopenia).

It is a real rabbit hole, and if you want my answer is that the optimal amount of protein is different for each individual, with a variation which goes probably from 0.6 to 1.6 g/kg/d, for some people it may even be less (if not strenuosly exercising) or more.

In a CR context, it's hard to answer, since decreased muscle mass is accepted, so the RDA of  0.8 g/kg/d might be applied, provided there is no lack of EAAs.

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I have 1.5g/kg according to cronometer and since it is all from plant sources (no grains, some nuts/pulses) I think I am on the lower safe edge. Animal sources are calculated with coefficient 0.9 and grains/legumes are rather ~0.5 for the availability of their proteins. For those, coming from other plants the availability could be much lower because they are attached to the carbs chains and not all of them are accessible for us. When I was on low calories experiment and I had 1g/kg with some small amount of animal protein sources I developed light version of anemia (may or may not be overlapped with low b12 also) and easy to distinguish wound healing impairment.

So I would suggest to always take into account the lowering coefficients for digestibility because RDA is calculated for 100% digestible proteins and on plants-only diets, depending on composition it could be possible to have it too low without noticing.

That is offcourse for the static situation of a midage man, balancing at the anemia entry point. All extra requirements (decease/tissue recovery, muscle growth, strong immunity to tackle something accute, age, lactating women and so on) there are higher numbers and perhaps it is better to have better sources.






just got my 24h urine test for the stuff I am interested in, this time I requested also urea to see the protein estimation for my regimen.


Protein intake by cronometer: 1.4g/kg

Largest protein contributors: peanuts, walnuts, yeast flakes, paprika, bell peppers, chickpeas, broccoli, orange

Blood urea: 13 mg/dl in the range of 17-43

24h urine urea: 226 mmol/24h in the range of 250-570

Water intake: ~4000ml/day (mostly from food, 450-480ml as coffee)

24H urine volume ~3300ml

Protein requirements last day: nothing special, also no hard excercising behindm just some running and ~3-4h of walking


A potential catch 1: reabsorption rate and overhydration - it is a bit more water than I am comfortable within my system these days, no idea if some extra influence from slight overhydration could affect the urea figures (https://acutecaretesting.org/en/articles/urea-and-the-clinical-value-of-measuring-blood-urea-concentration)

A potential catch 2: acid-base balance and nh4+ role in it - I have a lot of potassium to excrete, thus it could be the case I am "pushing out" a bit less urea due to pH/pK stabilization requirements, no idea if this guess is correct or not.

Anyway, these figures, could give a clue about plant proteines rough calculation based on published numbers. As my intuition told me - such an intake within such a regimen is a lower safety area (maybe not even safe in a longrun).




Edited by IgorF
some quantitative data for my case
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What Igor suggested about protein digestibility has been summarized in the concept of DIAAS, and has been discussed in the following post. There are also some suggestions beyond the cronometer figures (which do not account for ileal digestibility).



Edited by mccoy
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  • 2 weeks later...

Some additional thoughts on the topic based on own case.

There is a camp of researchers that are promoting an approach to get away from total protein figures and rather ensure some fewer individual AAs optimality focusing. Offcourse context-dependent optimality.

Being on the lower end of protein intake I was curious about blood AAs to see if something could be derived from them but it seems it works in one direction only - if there is abundance there will be visibility, but in slight deficiency the required things will be delivered via muscle tissue breakage (well, via shifting the balance of destruction/construction) thus serum AAs is not suitable to think about dietary tunings (if on low end).

With serum urea + 24h urine urea comes a figure about bigger picture and generally speaking it should be enough to tune the intake.

But I had in the past BCAA metabolites urine tests and I wanted to understand them but it took some time until I came to a possible explanation.

So, the first test

KIV     77.5%
KIC    118.4%
KMV  151%

And the second test

KIV     192,5%
KIC    100%
KMV  121%

After the first test I checked the book from a dedicated author for such tests trying to find potential reasons/tunes. The suggestion was a kind of inefficiency (I definitely have no so called MSUD genes) of an enzyme that move these ketoacids to an irreversible step for later transformations. The most suspicious is energy b-vitamins and alpha-lipoic acid. At least this was in the book and many articles I read.

So I ensured to back my intake with extra b1256 vits and a caps of ALA. After a long and stable timeframe of such backing up I did the second test. Except these tunes other things were the same. And the second test just mangled the values but they are still considerably higher than lab's range.

And after some reading of older papers from 80ies on earlier BCAA/BCKA studies I was able to find a pattern in the conclusions of several authors:

activity of en enzymatic complex that moves alpha-ketoacids to an irreversible destruction path is dependent on the preveois reversible BCAA<->BCKA "equilibrium" - increase (significant!) in BCAAs makes the enzyme more active and based on this healthy body "sunks" valuable BCAAs into energy or non-protein construction pathways, since my BCAAs are low on cronometer perhaps this is it.

So, in othe words - my intake could be not optimal and could require tuning or adjustments.

I will not change anything now, I am just sharing it as an illustration that topic is not so simple and the answers comes with an extra effort (this does not garantee however they are not wrong %))


The source books for articles that helped to understand it:


Branched Chain Amino and Keto Acids in Health and Disease,
pp. 100-111 (Karger, Basel 1984)
Effect of Diets on the Activity of Enzymes
Involved in Branched Chain α-Κeto Acid
K. Brand, S. Hauschildt, and J. Lüthje
Institute of Physiological Chemistry, University of Erlangen-Nuremberg,
Erlangen, FRG


Branched-chain α-Keto acid (BCKA) dehydrogenase plays an
important role in the catabolism of branched-chain amino acids
(BCAA) and BCKA by irreversibly committing these compounds to
the oxidative pathway. The activity of the hepatic BCKA dehydrogen-
ase is influenced by dietary factors [9, 10, 11, 15, 19, 24] and regu-
lated by a phosphorylatiόn-dephosphorylation mechanism [12, 14, 16,
20]. BCKA are actively decarboxylated in liver [1, 2, 4, 7, 8, 15, 17, 18,
22, 23] and the other organs [3]. The metabolic fate of orally adminis-
tered BCKA is mainly determined by the actual activity of BCKA de-
hydrogenase and BCAA aminotransferase present in liver and by the
Michaelis constants of these enzymes for the various BCKA.




The Metabolism and Metabolic Effects of Ketoacids
R. C. May, and W. E. Mitch
Renal Division, Emory University School of Medicine, Atlanta, Georgia 30322


We believe that much remains to be learned
concerning the metabolism of BCKA in both health
and disease. It is intriguing that experimental
conditions with excessive protein catabolism are
generally associated with abnormally high rates of
BCKA catabolism.

Indeed, part of the normal
adaptations to low-protein diets involve a decrease
in the catabolism of BCKA

. To what extent BCKA
are causally connected with those processes that
control overall protein metabolism, and hence ni-
trogen conservation, remains to be investigated. It
also remains unclear how BCKA (or specifically
KIC) modify protein metabolism and whether any
protein-sparing effect requires that it be adminis-
tered intravenously. These are questions of funda-
mental significance to understanding the regu-
lation of protein metabolism as well as under-
standing the rational use of branched-chain keto-
acid therapy.

(bold is mine)




Edited by IgorF
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At the end of such a complex picture, maybe very empirical observations have more practical sense.

Like, and this is a suggestion from Valter Longo, decide what your muscle mass is going to be (in realistic terms I would add), then, once you reached it by resistance exercise, decrease the protein intake until the circumference of the muscles decreases, then you are going below the optimal threshold (for that specific muscle mass) and have a clue of the optimal intake.

I don't know if it is a feasible suggestion since the measurement of muscle circumference by a taylor's tape is subject to error and half a  centimeter of muscle may constitute a significant increase or decrease. DEXA scan may be a more precise measurement but it cannot be done twice a week if your name is not Bryan Johnson.

Edited by mccoy
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