1. Introduction
muscle contractions, sarcopenia
SARCOPENIA
These authors contributed equally to this work.Background: Red beetroot is known to be a health-promoting food. However, little attention is placed on intestinal bioactive compound absorption. The aim of the study was to assess the urinary red beetroot juice (RBJ) intake biomarkers and possible differences in RBJ’s micronutrient absorption at rest or after physical exercise. Methods: This is a three-armed, single-blind study, involving seven healthy volunteers which were randomly divided into three groups and alternatively assigned to three experimental sessions: RBJ intake at rest, RBJ intake with physical activity, and placebo intake with physical activity. For each session, urine samples were collected before and 120, 180, and 240 min after the intake of RBJ or placebo. The same sampling times were employed for the experimental session at rest. The RBJ metabolic composition was also characterized to identify the urinary biomarkers derived from the intake. Results: 4-methylpyridine-2-carboxylic acid, dopamine-3-O-sulfate, glutamine, and 3-hydroxyisobutyrate were identified as RBJ intake biomarkers. Physical activity significantly increased only the dopamine-3-O-sulfate excretion 120 min after RBJ intake. Conclusions: Urinary dopamine-3-O-sulfate is related to RBJ dopamine content, while 4-methylpyridine-2-carboxylic acid is a betanin or betalamic acid catabolite. The different excretions of these metabolites following physical activity suggest a possible effect on the RBJ uptake depending on different transport processes through the mucosa, namely diffusion-mediated transport for dopamine and saturable transcellular transport for betalamic acid derivatives. These results open new perspectives in improving the absorption of natural bioactive molecules through physical activity.Red beetroot (RB), Interestingly, a consistent amount of dopamine has been found in fresh red beetroot or in juice [RB is also known to increase the blood levels of nitric oxide (NO), which is involved in multiple functions related to increased blood flow, gas exchange, mitochondrial efficiency, and strengthening of muscle contractions [All these findings have suggested RB as an ideal and healthy supplement in the field of sports and physical activity for the improvement of physical fitness [At the same time, it has been shown that exercise exerts positive effects on several aspects of health, such as sarcopenia [Consequently, for the latter, the absorption of different nutrients with exercise is expected even if the interaction between food and physical activity is very complex, also considering the scarce information on bioavailability of several bioactive compounds.In this regard, a better understanding of the digestive fate of bioactive food compounds should allow us to unravel the health promotion and the performance effects of physical activity [The aim of this study was to assess the effects of submaximal physical activity on the absorption of RB juice (RBJ) metabolites in healthy subjects. The urinary RBJ intake biomarkers, which are the metabolic products of characteristic molecules present in RBJ, were assessed, and metabolic profiles were characterized through NMR-based metabolomics at rest and after exercise.