Author(s): PASCHALIS, V., PROKOPIOU, N., KARYOFYLLIDOU, A.V., CHATZINIKOLAOU, P.N., MALLIOU, V.J., THEODOROU, A.A., MARGARITELIS, N.V., NIKOLAIDIS, M.G., Institution: NATIONAL AND KAPODISTRIAN UNIVERSITY OF ATHENS, Country: GREECE, Abstract-ID: 1702

INTRODUCTION:
Research in sports nutrition has uncovered that chronic exposure to acidic nutritional interventions may induce an acidotic state in the blood, potentially impairing exercise performance (Greenhaff et al., 1987; Hietavala et al. 2017). However, there is a lack of data concerning the acute effect of consuming a highly acidic beverage on physical performance. Thus, the aim of the present investigation was to evaluate whether the consumption of a substantial, acute dose of a highly acidic beverage, such as orange juice, could affect blood pH levels and consequently result in decline in performance.
METHODS:
Thirteen young, physically active males (n = 13; age 23 ± 3 years, body mass 74.3 ± 12.2 kg, height 175 ± 6 cm), volunteered in a randomized cross over design. During their first two visit to the laboratory, participants were randomly assigned to ingest 8 mL/kg body mass of either orange juice mixed with sodium bicarbonate (NaHCO3; neutral/control beverage) or simply orange juice (acidic beverage). Venous blood samples were collected before beverage ingestion and then at three-minute intervals up to the 15th minute. Subsequently, samples were collected every five minutes until the end of the 40-minute collection period. Two days after the baseline measurements, subjects underwent a Wingate test and a cycling VO2max assessment, at 15- and 30-min after the consumption of both types of juice, respectively. Blood samples were collected at rest as well as three and five min after completing the anaerobic capacity assessment.
RESULTS:
The pH of the neutral beverage (i.e., orange juice + NaHCO3) was 6.72 ± 0.32 and the pH of the acidic beverage (i.e., orange juice) was 3.50 ± 0.99. Over the 40 min period following beverage ingestion, neither beverage caused any significant changes in blood pH, and there were no significant differences in pH between the two types of beverages at any time point. Peak power output during the Wingate test was 930 ± 116 W and 920 ± 129 W after ingesting the neutral and the acidic beverages, respectively. Similarly, the fatigue index was 49 ± 8 % for the neutral beverage and 49 ± 7 % for acidic beverage with no significant differences between the two conditions (p>0.05). Additionally, the measurement of VO2max did not reveal any significant difference between the orange juice + NaHCO3 and orange juice alone (i.e., 49.8 ± 10.8 vs. 49.4 ± 11.7 ml/kg/min, respectively; p>0.05).
CONCLUSION:
The present findings unequivocally indicate that the acute consumption of a highly acidic beverage, such as orange juice, had no impact on either blood pH or physical performance. The artificial challenge we attempted to create appears to be nonexistent in real-life scenarios, suggesting that neutral beverages of a low acidic load may not influence blood pH and, by extension, physical performance.

References
Greenhaff et al. Eur J Appl Physiol Occup Physiol. 56: 331, 1987
Hietavala et al. Appl Physiol Nutr Metab 42: 1330, 2017.