This higher capacity was noted during the resting period, reported the authors in their study, published this week in the Journal of the International Society of Sports Nutrition.
Several studies in the past have linked higher antioxidant capacity to diminished potential oxidative stress produced by high volume and intensity endurance training (such as this study from 2015).
But the original goal of the researchers in this present study was to see whether or not the fruit juice would have any effect on iron metabolism—which it did not.
“The level of iron in the human body is affected not only by an adequate dietary intake of this element, but also by exercise-induced inflammation,” they wrote.
They cited a 2014 study by researchers in China which “demonstrated that moderate-intensity training has a beneficial effect on iron metabolism, whereas strenuous exercise may induce systemic inflammation.”
A high source of polyphenols
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The researchers postulated that the increase of antioxidant potential may be due to pomegranate’s high antioxidant activity compared to other food products widely recognized for their antioxidant properties, such as red wine and tea.
“The antioxidant potential of pomegranate fruit juice results from its high content of polyphenols, especially proanthocyanidins,” they wrote, adding that an increase of total antioxidant capacity after two weeks of pomegranate fruit juice supplementation was consistent with previous studies.
Though the juice did not exert a significant effect on other study parameters, such as inflammatory markers or iron metabolism, the researchers argued that this may be because of their highly trained study subjects (they were, after all, members of the National Polish Rowing Team).
“The lack of significant changes in [inflammatory markers] in our study subjects could perhaps be explained by their good adaptation to large training loads; this issue seems to be an interesting topic for future research.”
Study details
Nineteen members of the Polish Rowing Team participated in the double-blind, placebo-controlled study.
They were divided randomly into a supplemented group (10 rowers) receiving 50 ml of standardized pomegranate daily for two months, or the placebo group (9).
Participants then performed a 2000 m test on a rowing ergometer at the start of the project and end of follow-up period.
Researchers collected blood samples from the vein behind their elbows (antecubital) three times during the trial—prior to the exercise, one minute after the test, and following one day of recovery.
Source: Journal of the International Society of Sports Nutrition
Published online, https://doi.org/10.1186/s12970-018-0241-z
“The impact of supplementation with pomegranate fruit (Punica granatum L.) juice on selected antioxidant parameters and markers of iron metabolism in rowers”
Authors: A. Urbaniak