Plain language summary
Betaine nutritional supplementation is often used by individuals who want to increase their athletic performance as it has been hypothesised to increase muscle strength and power. However, studies on this have been inconsistent. One study has shown no benefit of supplementation on muscle strength, however two have shown a benefit of betaine on muscle endurance, which is essential to perform cross fit-based exercises. The aim of this study was to determine the effect of betaine on body composition, cross fit performance, muscle power, and certain hormones after 3 weeks of supplementation. The results showed that workout performance was improved with betaine supplementation, however this did not translate into changes in body composition. Testosterone levels were increased by betaine supplementation. Individuals who had genetic variations that meant that their betaine requirements may be higher showed no benefit of taking betaine for cross-fit performance or any of the outcomes measured. There was also no difference to any of the outcomes with differing betaine doses (2.5 and 5.0 g/d). It was concluded that betaine supplementation may improve cross-fit performance and testosterone levels. However individuals with genetic variations that may mean their requirements for betaine are higher showed no benefit of supplementation on cross-fit performance.
Abstract
BACKGROUND Because betaine (BET) supplementation may improve muscular strength and endurance, it seems plausible that BET will also influence CrossFit performance (CF). PURPOSE The aim of this study was to evaluate the effects of three weeks of BET supplementation on body composition, CF performance, muscle power in the Wingate anaerobic test (WAnT), and the concentrations of selected hormones. The secondary aims were to analyze the effectiveness of two different BET doses (2.5 and 5.0 g/d) and their interaction with the methylenetetrahydrofolate reductase (MTHFR) genotype. METHODS The study was designed in a double-blinded randomized cross-over fashion. Forty-three CF practitioners completed the entire study. CF performance was measured using the Fight Gone Bad (FGB) workout and muscle power was evaluated in a 30-second WAnT. Body composition was determined by air-displacement plethysmography. Blood was drawn to assess hormone concentrations. The C677T single nucleotide polymorphism (rs180113) in the MTHFR gene was analyzed. RESULTS FGB total improved with BET by 8.7 ± 13.6% (p < 0.001), but no significant changes were observed with placebo (- 0.4 ± 10.0%, p = 0.128). No changes were also observed in WAnT and body composition. After BET supplementation testosterone concentration increased by 7.0 ± 15.4% with BET (p = 0.046) (no change with placebo: 1.5 ± 19.6%, p = 0.884) but had no effect on concentrations of insulin-like growth factor or cortisol. Finally, there were no significant interactions between MTHFR genotype and BET dose in any outcome. CONCLUSIONS BET supplementation may improve CF performance and increase testosterone concentration. However, there was no evidence of a difference between dosages (2.5 and 5.0 g/d) and MTHFR genotypes. The trial was registered on clinicaltrials.gov (NCT03702205) on 10 October 2018.
Methodological quality
Jadad score
:
3
Allocation concealment
:
No
