"Beeting" personal bests in the gym with betaine Original paper

In this randomized crossover trial, supplementing with betaine improved CrossFit performance.

The effect of supplementation with betaine on exercise performance, body composition, and hormone levels.

The following outcomes were assessed:

• Performance on the Fight Gone Bad Test, which consists of 3 rounds of 5 different exercises performed for as many reps as possible for 1 minute, with no rest between exercises and 1 minute of rest between rounds.
• Power output during the 30-second Wingate test.
• Body composition, measured using BodPod.
• Hormone levels, including testosterone, IGF-1, and cortisol.

43 men (average age of 34) who participated in CrossFit for at least one year at different gyms in Poland.

In this 3-week randomized crossover trial, the participants were assigned to take a betaine supplement (either 2.5 or 5 grams per day) or a placebo. The interventions were separated by a 3-week washout period, and dietary intake was assessed using a 3-day food diary before and after each intervention.

Betaine supplementation, independent of dose, increased the number of repetitions performed for multiple (but not all) exercises in all 3 rounds, compared to no change in performance with placebo. Betaine increased the total number of repetitions performed across the 5 exercises in all rounds by 18.2 repetitions (a 7.2% increase), compared to no change with placebo. Betaine also increased total testosterone levels by 29 ng/dL, compared to no change with placebo.

The effects of betaine in recreational CrossFitters

Betaine, otherwise known as trimethylglycine, is a naturally occurring byproduct of sugar beet refinement. Besides sugar beets, beetroot, wheat, spinach, and shrimp are all good sources of betaine.^[1]

A small number of studies have examined the potential of betaine to improve various measures of exercise performance. The results have been mixed, but this seems to be a consequence of the exercise test used in the studies and how exercise performance was measured.

The summarized study reported an improvement in exercise performance with betaine, as evidenced by the completion of a greater number of repetitions during the Fight Gone Bad Test. This finding is in accordance with the hypothesis that betaine confers an ergogenic effect in resistance exercise protocols that challenge muscular endurance with high levels of metabolic stress.^[2] Other studies have reported that betaine can increase the number of repetitions performed during resistance exercise sessions that include multiple sets performed for a moderate to high number of repetitions (at least 8 repetitions) at close to momentary muscular failure.^[3][4][5] For more information about the potential mechanisms that may explain this ergogenic effect, see the previous Editor’s Pick published in June 2022. Betaine does not seem to be very useful for measures of strength and power, however. Betaine failed to improve power output in the summarized study, and this finding is in agreement with other studies on the topic.^[6].

Another finding in the present study that has been replicated in previous research is an increase in testosterone levels following betaine supplementation. Two recent studies in young, male athletes (average ages of 15 and 16) also reported an increase in testosterone levels following betaine supplementation, compared to a placebo.^[7][5]

In general, there’s a lack of evidence supporting the mechanism of action behind betaine’s potential to boost testosterone levels, and there aren’t any direct studies in humans investigating the effect. According to limited research in animals, betaine may have beneficial effects on testosterone levels because it protects testicular tissue from reactive oxygen species under stressful conditions.^[8] Further research is needed to uncover how exactly betaine increases testosterone levels.

From this data, a further question arises: is betaine’s effect on testosterone levels practically meaningful? Furthermore, do higher testosterone levels bolster resistance exercise-induced adaptations?

Testosterone is an anabolic, androgenic hormone, meaning that it promotes the development and maintenance of male sex characteristics (e.g., increased body and facial hair, deep voice), as well as muscle growth. The latter is evidenced by the fact that exogenous administration of testosterone enhances resistance exercise-induced gains in muscle mass,^[9] and administration of gonadotropin-releasing hormone analogs, which inhibit endogenous testosterone production, negatively affects muscle mass.^[10]

In further support of the possibility that higher testosterone levels bolster resistance exercise-induced adaptations, observational evidence indicates that higher testosterone levels are associated with higher amounts of lean body mass,^[11] and lower testosterone levels are associated with greater declines in muscle mass with aging.^[12][13]

However, direct evidence on the topic has refuted the hypothesis that naturally higher testosterone levels augment resistance exercise-induced gains in muscle mass. Multiple studies have reported that gains in muscle mass following a resistance exercise intervention are not associated with baseline testosterone levels in young men with no health conditions.^[14][15][16] Moreover, there was no difference between groups for the change in fat-free mass in the summarized study, nor was there a difference between groups for changes in lean body mass in a previous 14-week study that reported higher levels of testosterone following betaine supplementation compared to a placebo.^[7]

Ultimately, the range for what constitutes a healthy testosterone level varies. Within this large between-individual variability, a specific testosterone level may result in symptoms of low testosterone in one person and be sufficient for optimal health, performance, and quality of life in another. Although exogenous administration of testosterone to induce supraphysiological levels has a profound effect on muscle mass, even in the absence of resistance exercise,^[17] the available evidence indicates that, in men with normal testosterone and no health conditions, increasing testosterone levels within the normal physiological range does not augment resistance exercise-induced increases in muscle mass.