Powering Up With Plant Proteins

By Marie Spano, MS, RD, CSCS, CSSD

Spurred by documentaries and a desire to improve overall health, more consumers are opting for plant-based proteins than ever before. A market segment that was once dominated by soyfoods has since branched out to include proteins from a wide variety of plant foods from alfalfa protein to sacha inchi. As this category grows, consumers want to know how plant proteins compare nutritionally to whey, egg, and other animal-based proteins.

Why Are Plant Proteins Trending?
Vegetarians and vegans aren’t the only populations interested in plant proteins. In fact, the most rapidly growing segment of the population consuming them are individuals who simply want to reduce their intake of animal proteins in favor of a more plant-based diet. Plant proteins are growing in popularity due to consumer demand for quality nutrition choices and greater focus on the importance of protein for health, aging, and weight maintenance. In addition, segments of the population are concerned about sustainability—the environmental resources used and greenhouse gases produced, both of which can be tremendous when raising animals.1

An increasing variety of food and drink options packed with plant proteins, along with front-of-label messaging, lend greater visibility to this category. Plant-based product development shows no sign of slowing down given the array of options available. Supermarkets showcase several meat alternatives with different flavor profiles and textures. Plant milks are crowding the dairy section in grocery stores, and consumers can buy chips packed with plant proteins in addition to the more traditional powders and bars.2

Nutrient Profile of Plant Proteins
With the exception of soy, plant proteins typically are much lower in quality than animal proteins, as measured by the protein digestibility corrected amino acid score (PDCAAS). Whey, casein, soy, and egg all have a PDCAAS of 1. Beef comes in at 0.92; pea protein, 0.82; and black beans, 0.75. Whole hemp seeds have a PDCAAS between 0.49 and 0.53, and dehulled hemp seeds have a score between 0.63 and 0.66.3,4 The two main elements affecting the PDCAAS for plant foods rich in protein include antinutritional factors, which affect protein digestibility and amino acid availability, and the fact that all plant foods, apart from soy, are “incomplete” proteins, and therefore lack one or more essential amino acids in sufficient quantities.4 Examples of antinutritional factors include tannins in legumes and cereals and trypsin inhibitors in legumes.5,6 Cooking and soaking plant foods helps to reduce antinutrients. Though plant foods rich in protein generally score lower in protein quality, it’s unclear how separating the protein from plants, as is done for plant protein powder, impacts amino acid availability.

Some plant proteins contain a considerable amount of leucine. Leucine and total protein content are the strongest determinants of a protein’s effect on muscle protein synthesis (laying down of new proteins in muscle).7 Whey protein containing 30 g protein has about 4.5 g leucine, while soy protein isolate containing 30 g protein has 2.5 g leucine; peanut protein containing 30 g protein has 1.9 g leucine.8,9

Building and Maintaining Muscle
While some studies suggest that plant proteins don’t stimulate acute muscle protein synthesis to the extent that animal proteins do,10,11 others suggest that soy is effective at promoting skeletal muscle protein synthesis.12 Soy and wheat are the two most commonly studied plant proteins, yet a wide variety of other plant proteins are on the market. In addition, some studies didn’t control for total leucine content of the protein, and, therefore, a higher dose of soy may be comparable to whey when equating for leucine. There’s a lack of longer-term well-controlled studies in athletically trained individuals comparing plant-based proteins with whey.

If active clients rely on plants for their protein source, it’s best to choose a variety of plant protein sources during the day and to look for supplement powders that combine varied sources to get all of the essential amino acids. For instance, brown rice protein can be combined with pea protein powders. In addition, clients can consume enough total protein to get at least 3 g leucine per serving of protein to maximally stimulate muscle protein synthesis.7

— Marie Spano, MS, RD, CSCS, CSSD, is the sports nutritionist for the Atlanta Braves, Atlanta Falcons, and Atlanta Hawks. She’s the lead author of Nutrition for Sport, Exercise and Health. Visit her at www.mariespano.com.

References
1. Henchion M, Hayes M, Mullen AM, Fenelon M, Tiwari B. Future protein supply and demand: strategies and factors influencing a sustainable equilibrium. Foods. 2017;6(7):53.

2. Protein. SPINS website. http://www.spins.com/wp-content/uploads/2017/09/SPINSights-Protein.pdf

3. House JD, Neufeld J, Leson G. Evaluating the quality of protein from hemp seed (Cannabis sativa L.) products through the use of the protein digestibility-corrected amino acid score method. J Agric Food Chem. 2010;58(22):11801-11807.

4. Hoffman JR, Flavo MJ. Protein — which is best? J Sports Sci Med. 2004;3(3):118-130.

5. Deol JK, Bains K. Effect of household cooking methods on nutritional and anti nutritional factors in green cowpea (Vigna unguiculata) pods. J Food Sci Technol. 2010;47(5):579-581.

6. Seiquer I, Díaz-Alguacil J, Delgado-Andrade C, et al. Diets rich in Maillard reaction products affect protein digestibility in adolescent males aged 11-14 y. Am J Clin Nutr. 2006;83(5):1082-1088.

7. Phillips SM. The impact of protein quality on the promotion of resistance exercise-induced changes in muscle mass. Nutr Metab (Lond). 2016;13:64.

8. Babault N, Païzis C, Deley G, et al. Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, placebo-controlled clinical trial vs. whey protein. J Int Soc Sports Nutr. 2015;12(1):3.

9. United States Department of Agriculture. National Nutrient Database for Standard Reference, Release 28. https://ndb.nal.usda.gov/. Updated May 17, 2016.

10. van Vliet S, Burd NA, van Loon LJ. The skeletal muscle anabolic response to plant- versus animal-based protein consumption. J Nutr. 2015;145(9):1981-1991.

11. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.

12. Weinert DJ. Nutrition and muscle protein synthesis: a descriptive review. J Can Chiropr Assoc. 2009;53(3):186-193.

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