Salivary immunoglobulin A response at rest and after exercise following a 48 h period of fluid and/or energy restriction

The aim was to investigate the effects of a 48 h period of fluid, energy or combined fluid and energy restriction on salivary IgA (s-IgA) responses at rest and after exercise. Thirteen healthy males (age 21 (SEM 1) years) participated in four randomised 48 h trials. In the control trial participants received their estimated energy (12 154 (SEM 230) kJ/d) and water (3912 (SEM 140) ml/d) requirements. On fluid restriction (FR) participants received their energy requirements and 193 (SEM 19) ml water/d to drink and on energy restriction (ER) participants received their water requirements and 1214 (SEM 25) kJ/d. Fluid and energy restriction (F + ER) was a combination of FR and ER. After 48 It, participants performed a 30 min treadmill time trial (TT) followed by rehydration (0-2 h) and refeeding (2-6 h). Unstimulated saliva was collected at 0, 24 and 48 h, post-TT, and 2 and 6h post-TT. Saliva flow rate (sflw) and s-IgA (ELISA) remained unchanged in control conditions and on ER. However, 48h on FR decreased sflw (64%) which most probably accounted for the increase in s-IgA concentration (P<0.01). Despite a decrease in sflw (54%), sIgA concentration did not increase on F + ER, resulting in a decreased s-IgA secretion rate by 24 h (0 h: 20 (SEM 2); 24 h: 12 (SEM 2) mu g/ min; P < 0.01). Post-TT s-IgA secretion rate was not lower compared with 48h on any trial. s-IgA secretion rate returned to within Oh values by 6 It post-TT on F + ER. In conclusion, a 24-48 h period of combined F + ER decreased s-IgA secretion rate but normalisation occurred upon refeeding.