Protein Quality

(Part 2)

 How to get the best combination of protein quality and quantity

Tony Clark, CSO (Author) and Steve Fratini, PhD (Editor), November 20, 2023


In Part 1 of this article, we explored why simply focusing on the quantity of protein in a food is not sufficient.  Protein quality is also an important factor.  We explained why eating higher protein quality foods can help one avoid overeating and can help to prevent unwanted weight gain.   We define a food’s protein quality as being a function of the indispensable amino acids (IAAs) composition of the protein content in the food as compared to gold-standard food [1][2][3].  

In this original research article, we examine categories of common foods from the perspective of their protein quality and protein quantity and identify those food categories that have an optimal blend of both.  We assume the USDA MyPlate common food categories.  And, for all discussed food categories, we assume a serving size of 100 grams or 3.5 ounces for each food item, and for consistency we assume the daily IAA requirements for a person weighing 175 pounds. 

As shown in the accompanying chart, Figure 1 labeled “Protein Quality & Protein Quantity For Common Foods,” the food categories comprise the following:

Regarding the Figure 1 chart, the higher a food category appears in the chart, the higher its relative protein quantity, and the more directionally right a food category appears in the chart, the higher its relative protein quality.  Note that the food categories which appear in the upper-right quadrant of the Figure 1 chart have the most optimal protein quality and protein quantity characteristics.  One can generally consume less of the upper-right quadrant foods to meet their daily minimum IAA requirements; and by eating less this can be protective against unwanted weight gain.

Specifically, regarding the USDA food categories [4], we observe the following protein quality and protein quantity characteristics.

In summary, there are two important factors to consider when evaluating the protein content in a food: protein quantity and protein quality.  Protein quality is especially important for weight management purposes.  Eating higher protein quality foods is protective against overeating and helps to prevent unwanted weight gain.  Foods that are both protein dense (i.e., contain high amounts of protein) and that have high IAA Quality Scores should be considered by those looking to maximize protein consumption while minimizing calorie consumption.

* Generally, a mix of foods would be eaten in a balanced diet to meet one’s daily nutritional requirements.   Please consult your doctor or nutritionist to discuss your specific situation.

References

[1]  Dror, D.K. and Allen, L.H., Overview of Nutrients in Human Milk, Advances in Nutrition, Volume 9, Supplement 1, May 2018, https://www.sciencedirect.com/science/article/pii/S2161831322012753.

[2]  Report of an FAO Expert Consultation, Dietary protein quality evaluation in human nutrition, Food and Agriculture Organization of the United Nations, Rome, 2013, ISBN 978-92-5-107417-6.

[3]  Early modern human, Wikipedia, https://en.wikipedia.org/wiki/Early_modern_human, accessed on 4 September 2023. 

[4]  U.S. Department of Agriculture