Where Do You Get Your Protein From?

In virtually all studies, vegetable protein sources are superior to animal protein sources, with lower rates of heart disease and type 2 diabetes, and lower blood pressure. Despite this, in most European countries, the main contributor to the dietary protein intake of adults is meat and meat products, followed by grains and grain-based products, and milk and dairy products.

All foods contain protein, with few exceptions. The proportion and quality of protein differ from one food to another, but there are general misconceptions about what these differences are.

Proteins And Amino Acids

Proteins are built from amino acids joined together. Some of these amino acids are essential to us, meaning they cannot be synthesized by the body and therefore must be obtained from dietary sources. As such, the quality of a protein is determined by assessing its essential amino acid composition and its digestibility. Essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The non-essential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. Twenty amino acids in total.

Misconceptions About Protein Quality

A typical day of eating a variety of food includes adequate amounts of both essential and nonessential amino acids, regardless of the presence or absence of animal foods. There is a common misconception about whether plant foods contain all 20 amino acids. It is widely believed that plant foods miss specific essential amino acids, and are therefore not “complete”. But in fact, all plant foods contain all 20 dietary amino acids.

This misconception is probably based on the fact that lysine tends to be lower (not absent) in grains, and methionine tends to be lower (not absent) in beans. In that case, mixed meals can make up for differences of individual foods by complementing each another. Complementary foods do not need to be eaten during the same hour or even the same meal, but should be consumed within the same 24-hour period. However, it is generally not needed to make a conscious effort to complement plant protein intake. For instance, beans with grains is a pretty standard combination.

Protein Uptake And Intake Recommendations

In general, it appears that plant-based protein sources may be less well absorbed than animal-based proteins. The reason being the presence of antinutritional factors in plant protein sources. Antinutritional factors are substances present in foods other than nutrients that can interfere with digestion or uptake. For this reason, it has been suggested to consume more protein on a plant-based diet.

The current dietary guidelines suggest to consume 0.66 g protein/kg body weight per day; with an acceptable range of 10–35% of total calories from protein. However, when animal-protein is excluded, some studies suggest values of up to 1.0 g protein/kg body weight per day.

There are some exceptions however; soy protein and purified plant protein sources such as pea protein concentrate, possess comparable absorbtion with animal-based protein.

The Number Game

Suppose you prepare 125 g chicken, containing about 38 g protein, what does an equivalent portion of plant-protein look like? About 2 cups of cooked lentils. In comparison, 125 g chicken contains 215 kcal (or 455 if prepared with 2 tbsp oil), 2 cups of cooked lentils contain 460 kcal. The chicken contains an additional 100 mg of cholesterol and 1.5 g of saturated fat (triple that if prepared with 2 tbsp oil), whereas the lentils come with 23 g fibre, and 50% of the daily recommended intake of iron, zinc, and some of the B vitamins.

Plant Protein Sources

FoodProtein per 100 g
Pumpkin seeds (dried, uncooked) 30.2
Almonds (raw) 21.2
Tempeh 20.3
Flax seeds (raw)18.3
Tofu 17.3
Oats (rolled) 16.9
Walnuts (raw)15.2
Lentils (red, split, cooked) 9.0
Chickpeas (cooked)8.9
Kidney beans (cooked)8.4
Black beans (cooked) 8.2
Quinoa (cooked) 4.4
Buckwheat/Barley (cooked)3.4

Protein Sources

REFERENCES

Clifton, P. M. Protein and coronary heart disease: The role of different protein sources. Curr. Atheroscler. Rep. 13, 493–8 (2011)

European Food Safety Authority. Scientific Opinion on Dietary Reference Values for protein. (2012). Available at: https://efsa.onlinelibrary.wiley.co/doi/epdf/10.2903/j.efsa.2012.2557

Gardner, C. D., Hartle, J. C., Garrett, R. D., Offringa, L. C. & Wasserman, A. S. Maximizing the intersection of human health and the health of the environment with regard to the amount and type of protein produced and consumed in the United States. Nutr. Rev. 77, 197–215 (2019)

Rogerson, D. Vegan diets: practical advice for athletes and exercisers. J. Int. Soc. Sports Nutr. 14, 36 (2017)

Song, M. et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Intern. Med. 176, 1453–1463 (2016)

van Vliet, S., Burd, N. A. & van Loon, L. J. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. J. Nutr. 145, 1981–1991 (2015)