Importance of Soy Protein for Older, Plant-based Consumers

Importance of Soy Protein for Older, Plant-based Consumers

A new perspective by Domić et al.,1 published in Advances in Nutrition, proposes that a vegan diet increases the risk of an inadequate protein intake at an older age and that current strategies to improve the anabolic properties of plant-based foods are not feasible for many older adults. This perspective indirectly highlights the value soyfoods can provide for older individuals who consume plant-based diets.

As way of background, the U.S. RDA (0.8g/kg body weight) for older individuals (>65 years) is the same as it is for younger adults. However, to prevent sarcopenia, some experts recommend older adults consume  more than the RDA.2-5 Especially notable in this regard, is that the World Health Organization (WHO) recommends that the elderly consume approximately 25% more protein than non-elderly adults.6 If one accepts 56g/d as the male protein requirement for non-elderly adults, to meet the WHO recommendation for the elderly, requires an intake of 70g/d.

Among participants in the Adventist Health Study 2 (AHS 2), the protein intake of vegans was 72.3g/d (standardized to 2,000kcal/d with adjustments made for sex, race, and age).7 However, these values represent the intake of the entire cohort, which has a mean age of 59 years. Since elderly protein intake is lower than the intake of the non-elderly, it is reasonable to conclude that vegan protein intake may not meet the recommendations of the WHO.8

Furthermore, Domić et al.1 point out the quality of plant protein is lower than animal protein and, as such, vegans need to consume more protein than their non-vegan counterparts to meet the biological requirements for indispensable amino acids (IAA). To this point, Gorissen et al.9 observed that plant-based protein isolates exhibit on average an 11% lower IAA content than animal-based protein isolates. Also, Herreman et al.10 showed that when using the adult scoring pattern based on the digestible indispensable amino acid score (DIAAS), scores for egg, casein, whey, and pork exceeded 100 whereas of the 12 plant proteins examined, only soy and potato protein had scores of or near 100. (Several combinations of plant proteins were shown by Herreman et al.10 to receive scores of 100).

Several authors,11-13 although not all,14 have recommended that vegans and adherents of plant-based diets consume more protein than the RDA to account for the lower digestibility of plant protein.15 In fact, the Dutch Ministry of Health recommends a 1.3 times higher protein intake for all individuals ≥18 years following a vegan diet due to the suggested lower digestibility of protein from plant-based foods.16 To meet the Dutch recommendations (30% more) and the WHO recommendations (25% more), elderly male vegans need to consume 91g/d protein. Assuming a caloric intake of 2,000 calories, to consume 91g protein means the diet would need to be about 18% protein.  However, in the AHS 2, vegan diets were 14% protein.7 And, according to Lieberman et al.,17 among developed countries, mean protein intake represents about 16% of calories, although, of the 14 developed countries examined, two derived about 18% of their calories from protein.

One additional point made by Domić et al.1 is that plant foods tend to be more satiating than animal foods. They cite a study by Kristensen et al.,18 which showed that a high-protein legume-based meal lead to lower ratings of appetite, hunger, and prospective food intake, and higher ratings of satiation and a reduced ad libitum energy intake when compared to an isocaloric high-protein, meat-based meal. The point is that because legumes, which are an important source of protein in plant-based diets, are more satiating, they may limit caloric intake.

The above discussion emphasizes the importance of elderly vegans consuming some sources of high-quality protein. The high quality of soy protein has been demonstrated using both the protein digestibility corrected amino acid score (PDCAAS)19-21 and the digestible indispensable amino acid score (DIAAS).22 Plus, soybeans are higher in protein than other legumes.23

The importance of protein quality appears to be appreciated by at least a segment of consumers. In a recent survey of about 1,000 Americans 18-80 years of age, 34% chose high-quality protein as one of the three top reasons they choose plant-based protein.24 However, in a survey of approximately 300 Americans aged 18-56 years who exercise regularly and belong to households with income >$50,000, soy protein was rated similarly to wheat gluten and lower than peanut/tree nut protein, pea protein, whey, and collagen.25 With the exception of whey, these proteins are lower in quality than soy protein. in fact, wheat gluten is often cited as an example of a commonly consumed low-quality protein. Thus, there is a need to increase awareness that soy protein is the type of high-quality protein consumers seek.


  1. Domic J, Grootswagers P, van Loon LJC, de Groot L. Perspective: Vegan diets for older adults? A perspective on the potential impact on muscle mass and strength. Adv Nutr 2022.
  2. Traylor DA, Gorissen SHM, Phillips SM. Perspective: Protein requirements and optimal intakes in aging: Are we ready to recommend more than the recommended daily allowance? Adv Nutr 2018;9:171-82.
  3. Bauer J, Biolo G, Cederholm T, Cesari M, Cruz-Jentoft AJ, Morley JE, Phillips S, Sieber C, Stehle P, Teta D, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc 2013;14:542-59.
  4. Deutz NE, Bauer JM, Barazzoni R, Biolo G, Boirie Y, Bosy-Westphal A, Cederholm T, Cruz-Jentoft A, Krznaric Z, Nair KS, et al. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr 2014;33:929-36.
  5. Baum JI, Kim IY, Wolfe RR. Protein consumption and the elderly: What is the optimal level of intake? Nutrients 2016;8.
  6. World Health Organization & World Health Organization/Tufts University Consultation on Nutritional Guidelines for the Elderly (‎1998 : Boston, Mass.)‎. (‎2002)‎. Keep fit for life: meeting the nutritional needs of older persons. World Health Organization.
  7. Rizzo NS, Jaceldo-Siegl K, Sabate J, Fraser GE. Nutrient profiles of vegetarian and nonvegetarian dietary patterns. Journal of the Academy of Nutrition and Dietetics 2013;113:1610-9.
  8. Berryman CE, Lieberman HR, Fulgoni VL, 3rd, Pasiakos SM. Protein intake trends and conformity with the Dietary Reference Intakes in the United States: analysis of the National Health and Nutrition Examination Survey, 2001-2014. Am J Clin Nutr 2018;108:405-13.
  9. Gorissen SHM, Crombag JJR, Senden JMG, Waterval WAH, Bierau J, Verdijk LB, van Loon LJC. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids 2018;50:1685-95.
  10. Herreman L, Nommensen P, Pennings B, Laus MC. Comprehensive overview of the quality of plant- And animal-sourced proteins based on the digestible indispensable amino acid score. Food science & nutrition 2020;8:5379-91.
  11. Mariotti F. Plant protein, animal protein, and protein quality. In: Mariotti F, ed. Vegetarian and plant-based diets in health and disease prevention. Cambridge, MA: Academic Press; 2017:621-42.
  12. Mangels R, Messina V, Messina M. The Dietitian’s Guide to Vegetarian Diets. 3rd ed. Burlington, Massachusetts: Jones and Bartlett; 2011.
  13. Ciuris C, Lynch HM, Wharton C, Johnston CS. A comparison of dietary protein digestibility, based on DIAAS scoring, in vegetarian and non-vegetarian athletes. Nutrients 2019;11.
  14. Mariotti F, Gardner CD. Dietary protein and amino acids in vegetarian diets-A review. Nutrients 2019;11.
  15. Millward DJ, Layman DK, Tome D, Schaafsma G. Protein quality assessment: impact of expanding understanding of protein and amino acid needs for optimal health. Am J Clin Nutr 2008;87:1576S-81S.
  16. Health Council of the Netherlands. Dietary Reference Intakes: energy, proteins, fats and digestible carbohydrates. The Hague: Health Council of the Netherlands. 2001.
  17. Lieberman HR, Fulgoni VL, Agarwal S, Pasiakos SM, Berryman CE. Protein intake is more stable than carbohydrate or fat intake across various US demographic groups and international populations. Am J Clin Nutr 2020;112:180-6.
  18. Kristensen MD, Bendsen NT, Christensen SM, Astrup A, Raben A. Meals based on vegetable protein sources (beans and peas) are more satiating than meals based on animal protein sources (veal and pork) – a randomized cross-over meal test study. Food & nutrition research 2016;60:32634.
  19. Hughes GJ, Ryan DJ, Mukherjea R, Schasteen CS. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chemistry 2011;59:12707-12.
  20. Rutherfurd SM, Fanning AC, Miller BJ, Moughan PJ. Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. J Nutr 2015;145:372-9.
  21. Mathai JK, Liu Y, Stein HH. Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS). Br J Nutr 2017;117:490-9.
  22. Reynaud Y, Buffiere C, Cohade B, Vauris M, Liebermann K, Hafnaoui N, Lopez M, Souchon I, Dupont D, Remond D. True ileal amino acid digestibility and digestible indispensable amino acid scores (DIAASs) of plant-based protein foods. Food Chem 2020;338:128020.
  23. Messina MJ. Legumes and soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr 1999;70:439S-50S.
  24. Consumption Trends, Preferred Names and Perceptions of Plant Based Meat Alternatives. International Food Information Council. November 2021.
  25. Soy Fitness Partnership Program. USB TRACK & PROJECT NUMBER: Meal – Demand – Market Outreach. USB #2240-352-0511.

 This blog is sponsored by SNI Global and the United Soybean Board.

Dr. Mark Messina

Author Dr. Mark Messina

PhD in Nutrition, Director of Nutrition Science and Research, Soy Nutrition Institute Global. Expert in soyfoods and isoflavones.

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