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I'm wondering if the diaas concept can be used advantageously even  in those who practice CR. My first thought is: optimizing amino acid availability allows to decrease calories with minimum risk of malnutrition due to lack of adequate EAAs.

The DIAAS concept, from the wiki voice and a free review article.



Digestible Indispensable Amino Acid Score (DIAAS) is a protein quality method proposed in March 2013 by the Food and Agriculture Organization to replace the current protein ranking standard, the Protein Digestibility Corrected Amino Acid Score (PDCAAS).

The DIAAS accounts for amino acid digestibility at the end of the small intestine, providing a more accurate measure of the amounts of amino acids absorbed by the body and the protein’s contribution to human amino acid and nitrogen requirements. This is in contrast to the PDCAAS, which is based on an estimate of digestibility over the total digestive tract. Values stated using this method generally overestimate the amount of amino acids absorbed.[1]



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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952019/#:~:text=If a food item has,is between 75 and 99.

an the digestible indispensable amino acid score methodology decrease protein malnutrition




  • The new system for estimating protein quality of human foods, which is called “Digestible Indispensable Amino Acid Score” or DIAAS, allows for calculation of the amino acid quality of food proteins that are based on ileal digestibility rather than total tract digestibility and values for each amino acid may be calculated.
  • By recognizing the pig as an appropriate model for determining DIAAS values in human food proteins, a procedure for the standardized measurement of DIAAS values in a large number of food proteins has been established.
  • Because digestibility values for amino acids in individual food proteins are additive in mixed meals, DIAAS values for mixed meals may be calculated. By comparing DIAAS values of mixed meals to the requirements for digestible indispensable amino acid, the amino adequacy of the meal may be calculated.
  • Animal proteins such as meat and milk have greater DIAAS values than plant proteins, but by complementing plant proteins with low DIAAS values with animal proteins with greater DIAAS values, balanced meals that are adequate in all amino acids can be provided.
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With a further suggested reading, not freely available.


Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats

Affiliations expand


Background: The FAO has recommended replacing the protein digestibility-corrected amino acid score (PDCAAS) with the digestible indispensable amino acid score (DIAAS).

Objective: The objective of this study was to compare aspects underlying the calculation of the DIAAS and PDCAAS, including 1) fecal digestibility vs. ileal digestibility, 2) using a single nitrogen digestibility value for all amino acids, and 3) the effect of truncation. Truncated PDCAAS and untruncated DIAAS values calculated as formally defined were also compared and DIAAS data presented for 14 dietary protein sources.

Methods: Semisynthetic wheat starch-based diets were formulated to contain the test protein (as consumed by humans) source (whey- and soy-protein isolates, milk-, whey-, rice- and pea- protein concentrates, cooked kidney beans, roasted peanuts, cooked peas, corn-based breakfast cereal, cooked rice, cooked rolled oats, and wheat bran) as the sole nitrogen source and with an indigestible marker (titanium dioxide). Growing male rats (∼250 g bodyweight) were given a basal casein-based diet from day 1 to day 7 and then allocated (n = 6) to the test diets for day 8 to day 14 before ileal digesta were collected after the rats were killed. Total feces were collected from day 11 to day 14.

Results: True fecal nitrogen digestibility was different (P < 0.05; 10% difference on average) from true ileal nitrogen digestibility for 11 of the 14 protein sources. True ileal nitrogen digestibility was different (P < 0.05) from true ileal amino acid digestibility for almost half of the indispensable and conditionally indispensable amino acids (differences ranged from 0.9% to 400%). DIAAS values ranged from 0.01 for a corn-based cereal to 1.18 for milk protein concentrate.

Conclusion: Untruncated PDCAAS values were generally higher than a DIAAS values, especially for the poorer quality proteins; therefore, the reported differences in the scores are of potential practical importance for populations in which dietary protein intake may be marginal.

Keywords: DIAAS; PDCAAS; amino acid; ileal; protein quality.

© 2015 American Society for Nutrition.

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To cite just one possible application: the protein in wheat has a DIAAS of about 0.45, meaning that only 45% of it is absorbed in the ileum, the small intestine where protein is digested.

Hence: should we halve the protein contained in wheat (and most other cereals) when we track our food intake in cronometer?

Of course the discussion has innumerable ramifications and aspects. For example, if the classic studies on nitrogen balance from Randd et al. are true, then we don't need any score because nitrogen balance is the final result of it all and Randd et al considered cases of vegan or mixed intake. On the other side, the protein requirement statistical distribution has an ample variability, suggesting a potential role of ileal absorption, at least hypothetically.

Always hypothetically, eating dairy protein and eggs could be very advantageous since we could eat less protein at the same time making sure our basic requirements of EAAs, which is the most important thing when dealing with protein, are satisfied. The above is valid also for mixture of dairy products and other animal protein and cereals, in such a way upgrading the digestibility of the meal. I do not think it is the same thing as complementing EAAs by mixing beans and cereals.

Last but not least, since I have yet to study the theory, I may be easily missing something.


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One of the best recent articles on DIAAS is the following, freely available



Comprehensive overview of the quality of plant- And animalsourced proteins based on the digestible indispensable amino acid score



It is interesting to observe that soy protein seems to have a 100% DIAAS, similar to some animal protein. In a few words, if eating 0.66 g/kg/d (the average value for daily protein requirement) soy protein, on average we'll  sufficient absorption of all EAAS.

In my case, with a present bodyweight of 148 pounds = 67 kg, my EAAs needs would probably (on average) be satisfied with 44 grams of soy protein (or whatever other protein with 100% DIAAS).

That's how much protein is contained in about 1150 grams of soymilk, or 330 grams extra firm tofu (source: cronometer app). This is a good argument for a vegan diet; EAAs requirements are satisfied by soy products and mixtures of soy and other cereal protein (with soy prevalent over the cereals).

I remember that during my vegan stint I was able to gain some muscle mass by drinking soymilk and using soy protein and mixtures of cereal protein (often soymilk blended to pea or soy protein). 

Edited by mccoy
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The algorithm to calculate the DIAAS is explained in the BAiley and Stein article previously cited. In essence, as I think I've grasped, it's a method which serves to ensure that all EAAs are digested in sufficient amount while eating the daily average requirement of total protein of 0.66 g/kg/d. 


Since the DIAAS constitutes the minimum score among all EAAS, a value = > 100% ensures that a consumption of 0.66 g/kg/d of that specific food satisfies the need of EAAs for humans (the most recent DIAAS values are calculated from the ileal digestibility of pigs, which seem to have a very similar digestive system to humans).

Vice-versa, a value lesser than 100% means that there is at least one EAA which is not digested in a sufficient amount, hence if such a diet is repeated malnutrition could occur.

From the same article:


A DIAAS value greater than 100 indicates that if the food item is consumed in an amount equivalent to the estimated average requirement for protein (i.e., 0.66 g kg−1 d−1; IOM, 2002/2005), 100% or more of the human amino acid requirements will be met for the day. However, the protein content listed on the food label is not indicative of the quality of amino acids in the food (Figure 3). For example, peas may have a high quantity of protein, but with a DIAAS value of approximately 64 it has a low quality, whereas milk has both a high quantity of protein and high quality of amino acids with a DIAAS of 122. As a consequence, an individual would have to consume more than twice as much pea protein compared with milk protein to meet the human amino acid requirements. 


Edited by mccoy
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To those who think that the DIAAS score is not a valid concept in practice, as many healthy vegans (who do not eat very much soy protein) show, included many people in this forum: I added a possible explanation of this (provided by Don Layman) in the other thread.

Specifically, in vegans and people who eat high amounts of different fibers, the intestine may develop the ability to independently upgrade simple amino acids and basic nitrogen to essential amino acids, even like occurs in the digestive tract of ruminants.

This explanation was an incredible surprise to me! The problem is how do we know that our gut flora is actually upgrading that basic nitrogen?

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Practical application of the DIAAS concept (assuming it describes correctly what happens in the real world to humans).

One immediate application, especially useful in those who are practicing CR (possibly with protein moderation), is to minimize the protein intake and avoid chronic deficiencies in every single essential AAs.

One simple thing I checked is how much of the 100% DIAAS or above I have to take to satisfy all EAAs requirement in cronometer.

For example, 150 grams of 1% fat cottage cheese and 400 grams (less than a pint) of 1.5% fat milk provide over 100% requirement of the 9 essential amino acids (cysteine is at 40%, no wonder since it is the limiting AA in dairy products).

Total protein is 32 grams at 292 kcal. Since all those 9 EAAS are completely digested, I could stop here and add only vegetables and little else to my diet, maybe making sure to ingest some more cysteine with cruciferous veggies. Vegetables will provide more EAAS, but these will not be completely digested, although in combination with food with very high DIAAS score they'll increase their digestibility.

By adding one kg vegetables, namely 500 gr frozen spinach , 250 gr broccoli and 250 gr green cabbage (fresh and cooked), I'll reach the quantity of 61 g protein, which is over the official RDA (54 grams for my weight).

The above with only 607 kcal ingested. So, if I'm following CR, having prioritized the individual requirement of EAAS according to the DIAAS concept, I can now proceed to add more food to satisfy other requirements until the energy I wish, which may be, for my weight, 1600 kcal or more. By the way, micronutrients are already almost of each ones optimal, except niacin and zinc.





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Conversely, we can analyze the hypothesis of a vegan regimen based upon vegetable protein, namely cereals (cooked brown rice 250 gr, whole wheat bread 200g) and legumes (cooked lentils 250 gr). The results is according to cronometer is:

  • Protein RDA satisfied (54 g proteiin)
  • All EEAs satisfied but lysine (85%) and methionine (82%). 
  • 1100 kcal to start out with.

Besides the higher caloric intake, a major problem is  not only that lys and meth are below the accepted requirement according to cronometer, but that the actual digested amounts of those EAAS might be even less. In fact, the DIAAS of cereals is usually around 50% and the DIAAS of lentils is not publicized, at least as far as I could see. Legumes, except soy, range usually from 50 to 75% DIAAS. WE also should know the limiting AA of those foods, if those are Lys or Meth than weshould compute even less than 80-85% of requirement, maybe 50% requirement, which may lead us to a full-fledged deficiency.

EAAs can be complemented, but it is not a simple issue of eating other vegetables with more lysine and meth, because these may exhibit low digestibility as well.

The literature on the DIAAS score of mixtures is still insufficient. In the Herreman et al. article, a mixture of Pea and Wheat protein (60/40) has a DIAAS of 85%, this is the highest in legumes and cereals mixtures. 

Take home lesson to me is that:

  • Vegans would better eat soy which has a DIAAS score of 100%, so the amounts of EAAS reported by cronometer are those actually digested.
  • If not eating soy products for whatsoever reason, then there is a bifurcation:
  1. Estimate of the DIAAS of foods and mixtures, making up the lack of total digestibility with higher amounts.
  2. Go on without worrying about the intake of EAAS and become ruminants, that is hoping that the FGF21 hepatic signal activates the gut bioma to upgrade non-essential AAs and carbon-nitrogen molecules in food to EAAs. I would find this a sort of a gamble...
Edited by mccoy
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