Carbohydrate and fluid intake affect the saliva flow rate and IgA response to cycling

Purpose: The purpose of this study was to examine the effect of regular CHO beverage ingestion and restricted fluid intake on various salivary parameters during prolonged cycle exercise. Methods: In a randomized block design, 15 recreationally active men cycled for 2 h at 60% (V) over dot O-2max on three occasions, separated by 1 wk. On the CHO and placebo (PLA) treatments, subjects consumed either a glucose (60 g.L-1) or placebo drink before (400 mt), during (150 mt every 15 min), and after (400 mt) the exercise. On the restricted fluid intake (RFI) treatment subjects were given a total of 200 mt of placebo fluid to take as desired every 15-min during the exercise. Timed, unstimulated saliva samples were collected preexercise, at 1, 1.5, and 2 h of exercise and at 1 h postexercise. Blood samples were obtained from a subset of 8 subjects preexercise, postexercise, and at 1 h postexercise. Results: Postexercise plasma glucose levels were 18% and 20% lower on the PLA and RFI treatments, respectively, compared with the CHO treatment (P < 0.01). Saliva flow rates were significantly higher on the CHO treatment compared with the RFI treatment at 1.5 h and 2 h of exercise (P < 0.01 and P < 0.05, respectively). Salivary IgA (s-IgA) concentration was significantly lower on the CHO treatment compared with the RFI treatment throughout the exercise (P < 0.05). No other differences were seen between treatments for either saliva flow rate or s-IgA concentration. Neither s-IgA secretion rate, alpha -amylase activity, nor alpha -amylase secretion rate were affected by treatment. Conclusions: These findings suggest that CHO and fluid intake influence the s-IgA and saliva flow rate response to prolonged submaximal exercise.