Vegetarian Nutrition (VN) DPG Public Library

Heidi Lynch, Carol Johnston, Christopher Wharton
Journal: Nutrients
Published: 2018

Key Points

• Background: Many recent case studies have highlighted the success of prominent vegan endurance athletes such as ultra-runners and Ironman athletes.¹

  • Creatine levels are important in strength and power training² and it is typically higher in an omnivore diet.

  • Animal protein contains branched-chain amino acids which are needed in more concentrated amounts for muscle protein synthesis than what can be provided by plant protein sources.³

• Some studies have assessed the vegan or vegetarian diet’s impact on performance outcomes indirectly by measuring maximal oxygen uptake, strength, blood acid-base status, and acute muscle protein synthesis. Other studies have measured performance outcomes by measuring time to exhaustion when cycling or blood levels of glucose and lactic acid.

• In a systematic review done by Craddock et al., only eight studies directly examined the impact of a vegetarian diet on performance.⁴ Three of these studies focused on strength training and power, four assessed both anaerobic and aerobic performance, and one examined the impact of endurance exercise on immune markers.

• In one cross-sectional study, VO2 max was measured indirectly by a stress test, and a Wingate anaerobic test provided measurements of total power.⁵ The study found that neither aerobic nor anaerobic capacity significantly differed between vegetarians and omnivores.

• One study compared strength gains following a 12-week resistance training program between participants following a vegetarian (LOV) diet or omnivore diet.³ The study found that there were no significant differences between groups for strength on any test, except for knee extensions, which the LOV group had greater increases in strength. However, the prior physical fitness status of the participants was not considered which could impact outcomes.

• One cross-sectional study compared VO2 max, peak torque using an isokinetic dynamometer for knee extensions and flexions, and body composition between 27 vegetarian and 43 omnivore male and female endurance athletes.⁶ Participants maintained a 7-day food diary. Results showed that total protein intake was lower in the LOV group, but each group was consuming adequate protein for their body weight and for endurance athletes (1.2 – 1.5 g/kg). When doing leg extensions and flexions, peak torque did not differ significantly by diet group. VO2max did not differ significantly for males, but female vegetarian athletes had higher VO2max values compared to female omnivore athletes.

• Another study comparing the performance of vegetarians and omnivores based on their creatine levels found there were no significant differences in total work output between vegetarians and omnivores despite the lower total creatine levels in the vegetarian group.²

Conclusion

Based on the available research on the impact of plant-based diets on exercise performance, endurance and power does not appear to differ between vegetarians and omnivores.

References

1. Leischik R., Spelsberg N. Vegan triple-ironman (raw vegetables/fruits) Case Rep. Cardiol. 2014;2014 doi: 10.1155/2014/317246.

2. Burke D.G., Chilibeck P.D., Parise G., Candow D.G., Mahoney D., Tarnopolsky M. Effect of creatine and weight training on muscle creatine and performance in vegetarians. Med. Sci. Sports Exerc. 2003;35:1946–1955. doi: 10.1249/01.MSS.0000093614.17517.79.

3. van Vliet S., Burd N.A., van Loon L.J. The skeletal muscle anabolic response to plant-versus animal-based protein consumption. J. Nutr. 2015;145:1981–1991. doi: 10.3945/jn.114.204305.

4. Craddock J.C., Probst Y.C., Peoples G.E. Vegetarian and omnivorous nutrition—Comparing physical performance. Int. J. Sport Nutr. Exerc. Metab. 2016;26:212–220. doi: 10.1123/ijsnem.2015-0231.

5. Hanne N., Dlin R., Nrotstein A. Physical fitness, anthropometric and metabolic parameters in vegetarian athletes. J. Sports Med. Phys. Fit. 1986;26:180–185.

6. Lynch H.M., Wharton C.M., Johnston C.S. Cardiorespiratory fitness and peak torque differences between vegetarian and omnivore endurance athletes: A cross-sectional study. Nutrients. 2016;8:726. doi: 10.3390/nu8110726.