Protein shake-up

By Paul Gander

- Last updated on GMT

Related tags: Nutrition, Protein

Dairy protein firms have welcomed the new method
Dairy protein firms have welcomed the new method
Do new ways of assessing and scoring protein quality reflect the complexity of the debate? Paul Gander asks some of the experts

No doubt there is a formula correlating levels of disagreement among the members of a committee with the time taken to finalise a report that is acceptable to all. If so, then the two years taken to publish a recent Food and Agricultural Organisation (FAO) report on protein quality would probably yield a fairly high 'discord' score.

The 2011 FAO expert consultation was itself examining a different kind of scoring: the ways in which the nutritional efficiency of different proteins and amino acids (AAs) can be evaluated and rated. But the publication of the report earlier this year has sparked questions not only about the way the consultation was organised and funded, and how it has been reported, but more broadly about the rationale behind proposed changes to current methodology.

Unlike earlier FAO consultations, the 2011 event – organised in parallel with a conference – involved private as well as UN funding, according to one of the experts: emeritus professor at the University of Surrey, Joe Millward. "The part-funding by New Zealand's Riddet Institute and sections of the dairy industry is a new, not entirely satisfactory, development for FAO,"​ he says, pointing out that this leads unavoidably to questions about impartiality.

The report's recommendations (see bottom of page) have been enthusiastically welcomed by dairy protein businesses in particular. For example, nutrition manager at UK-based whey protein specialist Volac, Suzane Leser says: "For the first time, there will be an accurate method that will recognise the greater nutritional value of dairy proteins."

Best advice

Meanwhile, FAO's lead representative at the consultation, principal nutrition officer Barbara Burlingame, is quick to refute any suggestion that the organisation might have intended to "advantage or disadvantage any agricultural commodity or sector of the food industry"​. Of the final report she says: "It is simply a reflection of the best scientific advice available. FAO provides a neutral forum."

But if impartiality is an issue for Millward, so too is the transparency of the report – even though he helped to draft and sign it off. The report recommends a move away from the current system of nutritional quality assessment (Protein Digestibility Corrected Amino Acid Score, or PDCAAS) to the theoretically more accurate but more complex Digestible Indispensable Amino Acid Score (DIAAS). But it also establishes that there is still insufficient data to allow DIAAS to be used in practice.

Another 2011 participant, vice-chair of the consultation Dr Ricardo Uauy of the University of Chile, Santiago, explains that preliminary data for DIAAS is mostly based on studies on rats, as well as pigs.

"But the actual use of this concept requires validation of potentially useful animal models,"​ he says. "Until the research is done on humans – or a valid animal model has been established and data generated – then DIAAS will not be applied."

Millward, who was also one of the expert panel which helped to usher in PDCAAS in 1991, says that chair of the consultation Paul Moughan of Riddet was challenged at the 2011 meeting about this lack of evidence to support a change from PDCAAS to DIAAS. The question of transparency arises, he argues, because this fundamental dispute over evidence is not apparent to the casual reader of the report. Instead, it has been separated off into two post-consultation sub-committee reports.

Even the most avid reader of committee proceedings must at this point be thinking: does all this matter? In a few years' time, we may all be happily applying DIAAS scoring without worrying too much how we got there.


If nothing else, the process serves to illustrate how 'spin' can play as important a part in science as in politics. This operates on the relatively minor level of terminology, so that the report talks about applying DIAAS on the basis of faecal protein digestibility while awaiting ileal data. "This is a contradiction in terms,"​ says Millward. "What this means is simply the continued use of PDCAAS."

But it also works on the level of the bigger picture, and the colours in which it is painted. Riddet's Moughan has predicted that the necessary research to reinforce statistical relationships between ileal digestibility in pigs and in humans could be completed by spring 2014.

Uauy in Santiago foresees a longer process: "My view is that, even with optimal funding and several labs taking up this research agenda, it would take at least five to seven years before we have the evidence, and have sorted out the details of extrapolation to humans."

Burlingame at FAO predicts a similarly slow progression towards Codex (the body set up by the FAO to develop harmonised international food standards), which – with at least three different committees to consult, – typically "takes many years".

In the meantime, some believe the dairy protein industry is in fact less interested in the DIAAS system itself and more in the report's recommendation that truncation (or rounding down) of protein scores should be abandoned. Leser at Volac believes that both are important, and that the removal of truncation alongside new DIAAS data could provide the basis for European health claims relating to protein quality.

"Low quality protein sources and mixtures that will not be able to make a health or nutrition claim will be pushed to improve their nutritional profile by blending with proteins of higher value, such as dairy,"​ she explains.

It is easy to speculate that, by the time DIAAS is ready for implementation, the science around AA and protein efficiency may have moved on again. Millward argues, for instance, that the dairy industry tends to overplay the role of essential AAs, while downplaying the requirement for so-called "non-essential"​ AA nitrogen in human nutrition.

FAO's Burlingame has no doubts about the process so far, and expects to see "criticisms fly"​ as DIAAS progresses, albeit slowly, towards Codex. The same happened with consultations in areas such as diet and chronic disease, carbohydrates and food energy, she points out.

With specific reference to PDCAAS and DIAAS, she says: "If FAO can be criticised for something, it would be for waiting 20 years since the​ [original] recommendation before convening another consultation on protein quality measurement."

As budgets tighten, others will be paying closer attention to FAO's status as the "neutral forum"​ that Burlingame talks about, and watching for any sign that its processes are rather less 'business as usual' and rather more 'business'.

The expert consultation and report

The UN's Food and Agricultural Organisation (FAO) convened an Expert Consultation during 2011, following it up with a report, not published until earlier this year.

Both consultation and report compared the current Protein Digestibility Corrected Amino Acid Score (PDCAAS) and alternative Digestible Indispensable Amino Acid Score (DIAAS) systems of measuring the real benefits of particular proteins in human nutrition.

Expert debate about different assessment methods for proteins and individual amino acids (AAs) has been ongoing for over two decades, and certainly since FAO's adoption of PDCAAS in 1991.

This might appear a rather arcane discussion regarding where on their Odyssey through the body the availability and digestibility of AAs should most accurately and practically be measured.

DIAAS focuses on ileal as opposed to faecal protein digestibility.

But DIAAS also focuses, as its name suggests, on the most highly valued AAs.

Moreover, PDCAAS has been applied in conjunction with truncation, or the 'rounding down' of protein digestibility scores to 1 (or 100, depending on the scoring system used) when they exceed overall human dietary requirements.

This has tended to downplay the higher nutritional value of animal proteins in particular, and the dairy protein industry has long campaigned against it.

Now, in addition to the adoption of DIAAS, the FAO report has recommended a move away from truncation.

Click here to read FAO reports​ on dietary protein.

Related topics: Dairy, Proteins, non-dairy

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