The impact of vegan vs omnivorous diets on biomarkers of inflammation in muscle recovery : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand

Abstract

Background: Although vegan diets are becoming increasingly popular in New Zealand and globally, the implications for health and muscle recovery following exercise remain unclear. Complete and timely recovery improves athletic performance and decreases injury risk. Nutrition plays a vital role in the pathogenesis of muscle recovery as it influences inflammatory and immunomodulatory responses through altering ROS and cytokine production. However, research on whether vegan and omnivorous diets equivalently facilitate these processes is limited. Aim: To test whether individuals following a vegan diet present different levels of inflammation biomarkers in plasma after a bout of muscle damage-inducing exercise compared to individuals following an omnivorous diet. Methods: Twelve 18-45 year old males were stratified as vegan or omnivorous in this cross-sectional study. Participants completed a muscle damage-inducing lower body exercise protocol and 4-day food record. Muscle damage marker CK, pro-inflammatory biomarkers IL-1β, TNF-α, CRP and anti-inflammatory biomarkers IL-6 and IL-10 were analysed from blood at baseline and 0h, 1h, 3h, 24h, 48h and 72h time points post-protocol to assess muscle damage and indicators of inflammation. Results: Increased CK levels confirmed muscle damage as a result of the protocol, with omnivores displaying significantly higher absolute CK values to that of vegans (F = 8.076, P = 0.036). Plasma IL-1β absolute values among omnivores were also significantly higher (F = 1.010, P = 0.034). No significant difference in CRP or TNF-α absolute values (F = 2.913, P = 0.110 and F = 1.106, P = 0.377 respectively) or percentage change from baseline (F = 0.958, P = 0.373 and F = 1.153, P = 0.358 respectively) were found between diet groups, although TNF-α values among vegans remained higher across the time course. IL-6 and IL-10 levels were below detection levels. Dietary analysis showed vegans had significantly lower intake of trans fats (P = 0.046), cholesterol (P = 0.014) and significantly higher riboflavin (P = 0.010) compared to omnivores. There were also notable in differences in iodine and magnesium intake between groups. Conclusion: Fluctuations in biomarkers may be attributed to variations in nutrient intake between groups. However, the inflammatory response to the protocol was mild and no significant difference in inflammatory biomarkers of muscle recovery following exercise was found between vegans and omnivores.