Dairy excellent source of protein, say researchers
All dairy proteins tested in a recent study met Food and Agriculture Organization (FAO) standards as excellent/high-quality sources of protein for people six months of age or older, with DIAAS values of 100 or greater, according to the researchers at the University of Illinois. The study used pigs as a model to study the best way of evaluating protein quality in foods eaten by children, a method that was proposed by the United Nations FAO in 2011.
“Plant proteins are the primary sources of amino acids in many parts of the world, whereas animal proteins are the primary sources in other parts of the world. However, the composition and digestibility of these types of proteins differ,” says Dr. Hans H. Stein, professor of animal sciences at U of I and principal investigator of this research. The paper, “Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS)” was published in the February 2017 issue of the British Journal of Nutrition.
Stein and his team determined standardised ileal digestibility of crude protein and amino acids in eight sources of animal and plant protein: whey protein isolate, whey protein concentrate, milk protein concentrate, skimmed milk powder, pea protein concentrate, soy protein isolate, soy flour, and whole-grain wheat. Soy protein isolate and soy flour qualified as “good” sources of protein, with a score between 75 and 100. With scores below 75, pea protein concentrate and wheat did not qualify to make recommendations regarding protein quality.
“Compared with DIAAS, PDCAAS calculations tended to underestimate the protein value of high quality protein sources, and overestimate the value of lower quality sources,” says Stein. “Thus, to better meet protein requirements of humans, especially for people consuming diets that are low or marginal in digestible amino acids, DIAAS values should be used to estimate protein quality of foods.”
Funding for the research was provided by National Dairy Council, the non-profit organisation founded by America’s dairy farmers and funded by the national dairy checkoff program. The organisation had no input into the experimental design or analysis.
“The results of this pilot study indicate that dairy proteins may be an even higher quality source of protein compared to vegetable-based protein sources than previously thought,” says Dr. Greg Miller, chief science officer at NDC, on website Science Daily. “While using DIAAS is a newer concept and more research will be needed, one thing rings true – milk proteins are high quality and milk as a beverage has protein plus eight other essential nutrients, which is especially important when it comes to kids, because they need quality nutrition to help support their growth and development.”
