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:

• Fruit, including but not limited to apples, bananas, and oranges; 

• Vegetables, examples are asparagus, broccoli, and spinach; 

• Grains, including but not limited to bread, oatmeal, corn, noodles, and rice;

• Protein foods, examples are eggs, legumes, meat, and nuts/seeds; and

• Dairy, including but not limited to milk, cheese, and yogurt.

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.

• Meats (beef, chicken, fish, and pork), eggs, nuts/seeds, and legumes (beans, peas, and lentils) are generally the best foods from the perspective of maximizing both protein quality and protein quantity.  Among protein foods, meats are at the top of the list, offering the best combination of protein quality and quantity.  Meats have nearly 30 grams of protein per each 3.5 ounce serving and have some of the highest IAA Quality scores; which means that in some instances a couple of servings of meat can provide all of one’s daily minimum IAA requirements*.  Legumes, especially chickpeas, also have a very good protein quality and quantity profile.  Nuts/seeds have some of the highest relative protein quantity scores compared to all other common foods.  And, eggs have exceptional protein quality compared to all food options.

• Dairy foods have a high degree of variability regarding protein quality and protein quantity.  Some dairy foods have near-optimal protein quality, while other dairy foods have high protein quantity relative to other common foods.   Among dairy, cheese is a very good option for protein quantity at 24 grams (or more) of protein per each 3.5 ounce serving.   Milk and yogurt are also very good dairy options as both exhibit excellent relative protein quality.

• Grains generally have above average protein quality, but have some of the highest variability within a food category for protein quantity.   Oatmeal at 16 grams per each 3.5 ounce serving has above average protein quantity.   Rice on the other hand only has 3 grams of protein per each 3.5 ounce serving. 

• Vegetables have average protein quality among all foods and are among the lowest ranking foods for protein quantity.  Among vegetables, spinach, having 3 grams of protein per each 3.5 ounce serving, is one of the best vegetable options.  However, in comparison to meat, spinach has roughly 10% of the protein quantity of meat.  The implication is that those looking to obtain their daily minimum IAA requirements from just vegetables*, would need to eat dozens of servings of vegetables, which may lead to overeating and unwanted weight gain. 

• Fruit has the lowest protein quantity and quality characteristics.  Among fruit, avocados, at 2 grams of protein per 3.5 ounces, are one of the best fruit options.  One cannot reasonably expect to obtain their daily minimum IAA requirements from the consumption of fruit alone*.

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.