Citrus extract boosts anaerobic performance in 8-week study
The new research was published in the Journal of the International Society of Sports Nutrition. It was conducted by researchers associated with Maastricht University in the Netherlands, as well as with ingredient supplier BioActor BV, which manufactured the test material.
Two doses of branded ingredient
The researchers looked at two doses of the citrus flavonoid extract, branded as WATTS’UP. Subjects consumed either 400 mg or 500 mg of the extract daily for eight weeks. The study also included a placebo group. The branded extract was described as 90% hesperetin-7-O-rutinoside of which > 75% is composed of the 2S enantiomer. The two doses were equivalent to ingesting 0.7 or 0.9 liters of the juice of sweet oranges (Citrus sinensis), the researchers said.
The researchers noted that a moderate exercise stimulus produces reactive oxygen species in the mitochondria, which is part of the feedback loop that results in training adaptations. But too much of a good thing results in muscle damage and soreness. So the goal for sports nutrition ingredients has long been to find a way for athletes to train harder to enable greater muscle adaptation without creating the damage that can limit progress.
For the study researchers recruited 93 health young Dutch subjects of whom 79 completed the full study. The subjects were young recreational athletes, with slightly more men than women, who were exercising about 8 hours a week.
In addition to taking the twice-daily doses of the test materials or the placebo, subjects completed dietary questionnaires on the test days. No other dietary controls were included in the study, except to exclude those who were taking other supplements.
The full study consisted of eight weeks of supplementation as well as three exercise tests. One of these was conducted at the beginning to acquire baseline values, another was done at 4 weeks and another at 8 weeks. Subjects completed a Wingate anaerobic test on a cycling ergometer.
Anaerobic boost highest in 400 mg group
The researchers found that the citrus flavonoid extract resulted in greater anaerobic exercise capacity in the 400 mg group, with—curiously—a lesser effect in the 500 mg group. While the effect was small, it could still be significant, they said.
“Based on the result of the current study, strategic supplementation with CFE might be of interest for recreational athletes competing in sports that have a large anaerobic component, such as sprinters and track cyclists. Although the reported effects are small, these observed differences may be of high relevance and impact, if these results of this study in recreational athletes can be extrapolated to highly trained sports professionals. In elite athletes, small differences may determine winning or losing a competition,” they said.
In common with studies of many other dietary ingredients, the precise mechanisms of action of the observed effects remain murky and need further research, the authors said. Among the possible mechanism mention are boosts in NO production that could bring more oxygen to the muscles via vasodilation as well as a beneficial modulation of mitochondrial metabolism.
Source: Journal of the International Society of Sports Nutrition
18, Article number: 2 (2021)
The effect of citrus flavonoid extract supplementation on anaerobic capacity in moderately trained athletes: a randomized controlled trial
Authors: Van Iersel LE, et al.
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