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New Insights about Dietary Protein Requirements

By December 2, 2020 No Comments
New Insights about Dietary Protein Requirements

Evidence suggests consuming protein in excess of the recommended dietary allowance (RDA) can increase lean body mass. Evidence also indicates that high-quality plant protein, such as soy protein, can increase lean body mass as effectively as animal protein.

A systematic review that examined the relationship between protein intake and lean body mass sheds new light on dietary protein requirements. The findings of this review suggest increasing protein intake in excess of the RDA may increase or maintain lean body mass.1 Insight also comes from the findings from a clinical study that examined the impact of protein type and quantity on muscle protein synthesis.2 However, the authors of this study appear to have overlooked important findings published over the past several years, including a meta-analysis of clinical studies that showed soy protein supplementation leads to similar gains in muscle mass and strength as animal protein supplementation.3

The systematic review included randomized controlled trials evaluating the effects of protein intake on lean body mass. In total, 5,402 study participants from 105 articles were included in the analysis. Of the participants, 2,459 were female and 2,422 male; the sex of the remaining 530 participants was unknown (data not available). The mean age of the study participants ranged from 19 to 81 years, with an overall mean of 47.2 years.

The results showed that the mean increase in lean body mass associated with an increase in protein intake of 0.1 g/kg of body weight per day was 0.39 kg for total protein intakes below 1.3 g/kg/d and 0.12 kg for intakes above 1.3 g/kg/d. The authors concluded that slightly increasing current protein intake by 0.1 g/kg/d in a dose-dependent manner over a range of doses from 0.5 to 3.5 g/kg/d may increase or maintain lean body mass. Increasing protein intake was significantly effective for increasing lean body mass with or without resistance training.

These findings have potential implications for establishing future protein requirements.  If in fact, increasing protein intake above 0.8 g/kg body weight (the current RDA) can aid in increasing muscle mass, then there would appear to be significant reason for increasing the RDA.  Among young and middle-aged adults, decreased muscle mass ups the risk of chronic metabolic diseases such as type 2 diabetes and obesity.4,5 Moreover, among the elderly, sarcopenia (a progressive decrease in muscle mass with age) is a risk factor for fractures, physical disabilities, and frailty.6 The findings from this systematic review join other lines of evidence also suggesting the RDA needs to be increased.7-14

The aforementioned clinical study evaluated the effects of animal (71% from animal protein) or plant (mostly from mycoprotein) protein on daily myofibrillar protein synthesis rates in healthy older adults consuming a high-protein diet over the course of a three day intervention.2 The diets provided protein at a level of 1.8 g/kg body weight. The mycoprotein was produced via the fermentation of a particular fungus.

This study found that omnivorous or vegan-derived dietary protein sources can support equivalent rested and exercised daily myofibrillar protein synthesis rates. The authors concluded that their data “… indicate that obtaining dietary protein from animal-derived sources is not an essential prerequisite to support daily myofibrillar protein synthesis rates in older adults.” While this conclusion is justified based on the results, it is not particularly informative.

It has already been demonstrated that supplementation with large amounts of animal or plant protein leads to similar gains in strength and muscle mass.15,16 Providing large amounts of protein overcomes differences in plant and animal proteins that are seen when smaller amounts of protein are provided. More importantly, based on their meta-regression, a team of experts concluded that for building muscle, the key is protein amount, not protein type.17 This conclusion is consistent with the results of a meta-analysis that included 9 clinical trials which found that soy protein supplementation leads to similar gains in muscle mass and strength as supplementation with animal protein, including whey protein.3

References

  1. Tagawa R, Watanabe D, Ito K, et al. Dose–response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2020.
  2. Monteyne AJ, Dunlop MV, Machin DJ, et al. A mycoprotein based high-protein vegan diet supports equivalent daily myofibrillar protein synthesis rates compared with an isonitrogenous omnivorous diet in older adults: a randomized controlled trial. Br J Nutr. 20201-35.
  3. Messina M, Lynch H, Dickinson JM, et al. No difference between the effects of supplementing with soy protein versus animal protein on gains in muscle mass and strength in response to resistance exercise. International journal of sport nutrition and exercise metabolism. 2018;28(6):674-85.
  4. Park SW, Goodpaster BH, Strotmeyer ES, et al. Accelerated loss of skeletal muscle strength in older adults with type 2 diabetes: the health, aging, and body composition study. Diabetes Care. 2007;30(6):1507-12.
  5. Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006;84(3):475-82.
  6. Walrand S, Boirie Y. Optimizing protein intake in aging. Current opinion in clinical nutrition and metabolic care. 2005;8(1):89-94.
  7. Bandegan A, Courtney-Martin G, Rafii M, et al. Indicator amino acid-derived estimate of dietary protein requirement for male bodybuilders on a nontraining day is several-fold greater than the current recommended dietary allowance. J Nutr. 2017;147(5):850-7.
  8. Bandegan A, Courtney-Martin G, Rafii M, et al. Indicator amino acid oxidation protein requirement estimate in endurance-trained men 24 h postexercise exceeds both the EAR and current athlete guidelines. American journal of physiology Endocrinology and metabolism. 2019;316(5):E741-E8.
  9. Rafii M, Chapman K, Elango R, et al. Dietary protein requirement of men >65 years old determined by the indicator amino acid oxidation technique is higher than the current estimated average requirement. J Nutr. 2016;146681-7.
  10. Rafii M, Chapman K, Owens J, et al. Dietary protein requirement of female adults >65 years determined by the indicator amino acid oxidation technique is higher than current recommendations. J Nutr. 2015;145(1):18-24.
  11. Elango R, Humayun MA, Ball RO, et al. Protein requirement of healthy school-age children determined by the indicator amino acid oxidation method. Am J Clin Nutr. 2011;94(6):1545-52.
  12. Humayun MA, Elango R, Ball RO, et al. Reevaluation of the protein requirement in young men with the indicator amino acid oxidation technique. Am J Clin Nutr. 2007;86(4):995-1002.
  13. Stephens TV, Payne M, Ball RO, et al. Protein requirements of healthy pregnant women during early and late gestation are higher than current recommendations. J Nutr. 2015;145(1):73-8.
  14. Tang M, McCabe GP, Elango R, et al. Assessment of protein requirement in octogenarian women with use of the indicator amino acid oxidation technique. Am J Clin Nutr. 2014;99(4):891-8.
  15. Babault N, Paizis 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. Journal of the International Society of Sports Nutrition. 2015;12(1):3.
  16. Joy JM, Lowery RP, Wilson JM, et al. The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutrition journal. 2013;12(1):86.
  17. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2017;52376-84.
Dr. Mark Messina

Author Dr. Mark Messina

PhD in Nutrition, Executive Director, Soy Nutrition Institute. Expert in soyfoods and isoflavones.

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