Protein is important for many physiological reasons. As vegan diets and plant-based protein products have become more and more popular, the question arising is how good they are in satisfying human nutritional needs (1).

Well-known examples of plant proteins are beans, seeds (such as pumpkin and flaxseed), grains/starchy food (like potato, rice and quinoa) and proteins from pulses like pea and lentil. All protein, as well as the protein within plants, consist of building blocks called amino acids. Protein that contains all the essential amino acids in the amounts that our body needs, is called complete protein. Unfortunately, many plant proteins (with some exceptions like soya protein) tend to be incomplete and lack some essential amino acids. Amino acids, like lysine, methionine, isoleucine, threonine and tryptophan, are the building blocks for many physiological functions in our body (2). For example, cereals are usually low in lysine, but may contain a higher amount of methionine and legumes may have not enough methionine but have high concentrations of lysine. Therefore, a plant-based diet should contain a well-balanced mixture of plant proteins, so that you can get a complete, high-quality protein source.

In addition, it is important to remember the total amount of plant proteins when they are solely consumed. Although plant protein sources may have a comparable amount of protein to animal sources, their bioavailability (ability of the body to effectively digest and absorb them), can be lower than that of animal protein. For that reason, protein intake recommendations for vegans and vegetarians is about 10% higher than diets containing animal products (3, 4).

Did you know that  ground beef contains about 18% protein, whereas lentils contain about 25% protein (5)? Peas contain 20-25% protein and pea protein isolates can contain up to 94% protein (6-8). Flaxseed contains about 18% protein and grains/starchy foods are usually lower in protein. However, quinoa contains about 14% protein, which is close to the protein content of wheat but higher than most foods in this category such as rice, corn and rye - raw rice contains about 7% protein (5).

When it comes to weight management, it may be beneficial to adopt a plant-based diet. This is because vegetarian diets are associated with a reduced risk of obesity, compared to diets that contain meat (9, 10).  In addition, vegan diets are also associated with a reduced risk of cardiovascular diseases and type 2 diabetes (10-14). One of the reasons for this is because these diets are usually higher in fibre  and have a more favourable fat balance with less saturated fats (14-16). An increased amount of plant-based protein alone may have positive effects on your health (17-22). Other common protein sources such as soya and dairy, pea, quinoa, flaxseed and rice may be a nutritious alternative for those with allergies (23). As if all the above benefits weren’t enough, plant-proteins are also more ‘green,’ as switching from animal to plant protein brings substantial benefits for the health of our planet (16, 24).

References

1. The Good Food Institute. The Plant-Based Meat, Eggs, and Dairy State of the Industry Report 2020 [Available from: https://www.gfi.org/blog-state-of-the-industry-2020.
2. Churchward-Venne, Pinckaers PJM, Smeets JSJ, Peeters WM, Zorenc AH, Schierbeek H, et al. Myofibrillar and Mitochondrial Protein Synthesis Rates Do Not Differ in Young Men Following the Ingestion of Carbohydrate with Whey, Soy, or Leucine-Enriched Soy Protein after Concurrent Resistance- and Endurance-Type Exercise. J Nutr. 2019;149(2):210-20.
3. Agnoli C, Baroni L, Bertini I, Ciappellano S, Fabbri A, Papa M, et al. Position Paper on Vegetarian Diets from the Working Group of the Italian Society of Human Nutrition2017.
4. Craig WJ, Mangels AR. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009;109(7):1266-82.
5. FoodData Central [Internet]. US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory.  [cited 21-06-2020]. Available from: https://fdc.nal.usda.gov/fdc-app.html#/.
6. Lu ZX, He JF, Zhang YC, Bing DJ. Composition, physicochemical properties of pea protein and its application in functional foods. Critical Reviews in Food Science and Nutrition. 2020;60(15):2593-605.
7. Sandberg AS. 15 - Developing functional ingredients: a case study of pea protein. In: Saarela M, editor. Functional Foods (Second Edition): Woodhead Publishing; 2011. p. 358-82.
8. Gorissen SH, Crombag JJ, Senden JM, Waterval WH, Bierau J, Verdijk LB, et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino acids. 2018;50(12):1685-95.
9. Appleby, Key. The long-term health of vegetarians and vegans. J Proceedings of the Nutrition Society. 2016;75(3):287-93.
10. Huang RY, Huang CC, Hu FB, Chavarro JE. Vegetarian Diets and Weight Reduction: a Meta-Analysis of Randomized Controlled Trials. Journal of general internal medicine. 2016;31(1):109-16.
11. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics. 2016;116(12):1970-80.
12. Satija A, Bhupathiraju SN, Rimm EB, Spiegelman D, Chiuve SE, Borgi L, et al. Plant-Based Dietary Patterns and Incidence of Type 2 Diabetes in US Men and Women: Results from Three Prospective Cohort Studies. PLOS Medicine. 2016;13(6):e1002039.
13. Satija A, Bhupathiraju SN, Spiegelman D, Chiuve SE, Manson JE, Willett WC, et al. Plant-Based Diets and the Risk of Coronary Heart Disease in US Adults. 2017;31(1_supplement):167.4-.4.
14. Appleby PN, Key TJ. The long-term health of vegetarians and vegans. The Proceedings of the Nutrition Society. 2016;75(3):287-93.
15. Craig WJ. Health effects of vegan diets. The American journal of clinical nutrition. 2009;89(5):1627S-33S.
16. Willett W, Rockstrom J, Loken B, Springmann M, Lang T, Vermeulen S, et al. Food in the Anthropocene: the EAT-Lancet Commission on healthy diets from sustainable food systems. Lancet (London, England). 2019.
17. Pedersen AN, Kondrup J, Børsheim E. Health effects of protein intake in healthy adults: a systematic literature review. Food & nutrition research. 2013;57:10.3402/fnr.v57i0.21245.
18. Song M, Fung TT, Hu FB, Willett WC, Longo VD, Chan AT, et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA internal medicine. 2016;176(10):1453-63.
19. Tielemans SM, Altorf-van der Kuil W, Engberink MF, Brink EJ, van Baak MA, Bakker SJ, et al. Intake of total protein, plant protein and animal protein in relation to blood pressure: a meta-analysis of observational and intervention studies. J Hum Hypertens. 2013;27(9):564-71.
20. Lonnie M, Laurie I, Myers M, Horgan G, Russell WR, Johnstone AM. Exploring Health-Promoting Attributes of Plant Proteins as a Functional Ingredient for the Food Sector: A Systematic Review of Human Interventional Studies. Nutrients. 2020;12(8).
21. Chalvon-Demersay T, Azzout-Marniche D, Arfsten J, Egli L, Gaudichon C, Karagounis LG, et al. A Systematic Review of the Effects of Plant Compared with Animal Protein Sources on Features of Metabolic Syndrome. The Journal of nutrition. 2017;147(3):281-92.
22. Shang X, Scott D, Hodge AM, English DR, Giles GG, Ebeling PR, et al. Dietary protein intake and risk of type 2 diabetes: results from the Melbourne Collaborative Cohort Study and a meta-analysis of prospective studies. The American journal of clinical nutrition. 2016;104(5):1352-65.
23. EFSA. 1169/2011 of the European Parliament and of the Council of 25 October 2011 on the provision of food information to consumers. Official Journal of the European Union. 2011;304.
24. Aleksandrowicz L, Green R, Joy EJM, Smith P, Haines A. The Impacts of Dietary Change on Greenhouse Gas Emissions, Land Use, Water Use, and Health: A Systematic Review. PLOS ONE. 2016;11(11):e0165797.