I’ll address leucine in the final part of the Amino Acid Profile series but the short-answer is that adding a couple of grams to meals or post-workout shakes is just so much bullshit. Just like 99% of what’s in the sports supplement industry.

That’s what I meant by it being typical T-nation crap.

Lyle

This may be not the place, but I have to ask you what you were referring to when you said: “But short answer: of course it’s crap. Typical t-nation, bodybuilding comic book crap.”

I respect BOTH you and T-Nation (which is by far the best site on the Internet and has great minds on it) so I am very curious to hear your insights on where you think T-Nation (or perhaps one of their authors) is mistaken.

Realize that I’m trying to keep this article from turning into my protein book so I left out some details. Assuming the Wiki is remotely accurate, PDCAAS is defined as

“Using the PDCAAS method, the protein quality rankings are determined by comparing the amino acid profile of the specific food protein against a standard amino acid profile with the highest possible score being a 1.0.”

To my knowledge, it’s not just the essentials but I”d have to dig into the literature to be sure of that.

The reason that the AA profile of a 2-5 year old was chosen is because they show the highest overall requirements for essential AA’s (older individuals actually show lower requirements in both absolute terms and amino acid requirements).

This represents the fact that kids are growing at a fast rate (relatively speaking). So any protein that meets their requirements should meet (in theory anyhow) the needs of adults.

I’d note that this doesn’t necessarily apply to athletes (none of the methods do, it’s entirely possible that a specific athlete requires more or less of a given amino acid, this is discussed in detail in the Protein Book of course). So rounding to 1.0 based on assumptions about growing kids may not be relevant to folks involved in heavy training. Since that latter group is what I primarily focus on, that’s who I base some of my conclusions on.

As well, there is some literature suggesting that oxidation of amino acids has its own beneficial effects so rounding b/c oxidation increases above certain levels may be a flawed idea as well.

My definition of NPU comes from Groff and Gropper’s nutrition text and states “NPU measures retention of food nitrogen consumed rather than retention of food nitrogen absorbed.”

Meal frequency is detailed (an entire chapter) in the Protein Book although I’ll probably touch on it eventually. You might check the research review on the site about Meal Frequency.

While endurance athletes often engage in goofy eating patterns, I’d be surprised if any lived on single poor sources of protein like that.

Thanks for the comment,
Lyle

My understanding is that the PDCAAS uses essential amino acid requirements for a 2-5 year old as a reference, with 1.0 representing the maximum score as post-digestion this protein provides 100% or more of essential amino requirements and amino acids beyond this point exceed requirements and are excreted or stored as body fat rather than utilised for protein synthesis. So even if the food (whey, egg and some meats would fall into this category) could supply more amino acids in excess of requirement, the score is still 1.0, and rounded down for the reasons stated above.

The utility of proteins with a “true” PDCAAS score of greater than 1.0 is in complementing other proteins of lesser quality so obviously the PDCAAS score is a reflection of the test protein individually/in isolation, and the true usefulness of a protein in the diet is probably better reflected by a combination of the PDCAAS and the biological value and other measures.

From what I understand, the amino acid requirement patterns for 2-5 year old are elevated for all essential amino acids when compared to adolesecent and adult populations, and as such a PDCAAS score of 1.0 using 2-5 year olds as a reference pattern indicates that the protein will be equally if not better digested in other populations (see “Energy and Protein Requirements, Report of the Joint FAO/WHO/UNU Expert Consultation” at http://www.fao.org/docrep/003/AA040E/AA040E05.htm#ch5.6 for the table of figures), and that the amino acid profile will be sufficient to meet requirements, though it could easily be in excess and is therefore obviously not exact.

As the study you mentined hinted at, proteins like soy protein with a PDCAAS of 1.0 if consumed as a sole protein source can fulfill protein requirements when consumed in the requisite amount (daily protein requirement in grams). Obviously this is purely hypothetical as no one protein source is likely to be the sole source in the diet.

Also, my understanding was that NPU = (True digestibilty X BV) and therefore DOES take into account digestibilty while in fact BV is a measure of the protein that HAS been absorbed and how it is used, but DOES NOT account for protein that has not been absorbed and therefore does not account for absorption/digestibilty (the definitions of BV and NPU you give seem almost in reverse to what I understand).

I’d be interested to hear if you could expand on the effects of protein feeding freqency, low calorie diets and other factors similar to those mentioned here http://www.fao.org/DOCREP/MEETING/004/M2835E/M2835E00.HTM on protein absorption.

Also, for endurance athletes with high CHO and protein requirements do you think it possible that protein quality can be an issue as most protein is coming from low quality sources e.g. wheat and large volumes of these foods are almost a necessity, while protein intakes are still up to double that of a normal population.

Thanks,

Tim

Wait until the next bit, amino acid profile. I’ll touch on this a bit.

But short answer: of course it’s crap. Typical t-nation, bodybuilding comic book crap.

Lyle