• Dr Emma Derbyshire

A New Outlook on Protein Quality

The current definitions of protein quality are defined by biochemistry and metabolic matrices and are now deemed to be obsolete, inaccurate and potential harmful to public and planetary health. This is because they do not take into consideration the net effect of dietary protein on human health nor the environment.

Present definitions of protein quality are based on the ability of a dietary protein’s ability to achieve defined metabolic actions, as well as the protein’s ability to provide specific essential amino acid profiles for protein synthesis and growth.

Thus, the term ‘protein quality’ is now deemed to be misleading, as it tends to rely on evaluations of ‘single foods’ rather than whole diets and also implies superiority. Here we present new research and viewpoints recently published in Advances in Nutrition.

Protein Quality and Human Health

The public depend on precise, accurate and easy to understand nutritional information to make food choices that benefit their health and longevity. Research has shown that protein and amino acids have a complex role in the regulation of body composition and bone health, gastrointestinal health and microflora, cell signalling, glucose homeostasis and satiety.

In recent times both dietary fat and carbohydrate have been criticised in the media in terms of nutrition and healthy food choices. This has resulted in a popular concept that protein is good and can be eaten in large quantities without considering wider environmental implications.

Protein Quality and the Environment

In addition to human health, it is now known that there are environmental impacts of foods, from carbon emissions to water utilisation. Animal farming has been estimate to contribute to 14.5% of human-made global greenhouse gas emissions. Subsequently there is a need for more sustainable food systems which more widely considers health, affordability and environmental issues.

Updating the Definition of Protein Quality

A new pool of thought published by five leading scientists in Advances in Nutrition is that the definition of protein quality is in need of an update. They propose a new definition that incorporates quality of health and environmental outcomes associated with specific food sources of protein. In their paper the scientists demonstrate how this new definition has been compiled into a metric that could be applied to national and food regulatory labelling systems. Hence, the novel definition on protein quality now includes:

• The concentration of protein and individual amino acids in the food. • An assessment of the evidence of health outcomes associated with consumption of the food. • An assessment of potential environmental impacts of producing the food.


The proposed updated definition of protein quality incorporates health and environmental outcomes that are associated with different protein food sources. It is anticipated that this more rounded approach could help scientists, and the public alike, to better recognise the value of a range of proteins and allow people to eat for their own health and the health of the environment.


Katz DL et al. (2019) Perspective: The Public Health Case for Modernizing the Definition of Protein Quality. Adv Nutr May 8.

Gerber PJ et al. (2013) Tackling climate change through livestock: a global assessment of emissions and mitigation opportunities. Rome: FAO. Available from http://www. fao.org/3/a-i3437e.pdf.

Lewis JL (2012) The regulation of protein content and quality in national and international food standards. Br J Nutr 108 Suppl 2:S212-21.

Millward DJ et al. (2008) Protein quality assessment: impact of expanding understanding of protein and amino acid needs for optimal health. Am J Clin Nutr 2008;87(5):1576S-81S.

This work was supported by Marlow Foods Ltd. The content of the insight has been written independently.ylity