Pharmacokinetics of fluoride in human adults: The effect of exercise

The literature is sparse in terms of the effect of exercise on the pharmacokinetics of fluoride (F) in humans. In a 4-treatment repeated measures cross-over study, we investigated F pharmacokinetics following no exercise (control) and three exercise intensity conditions (light, moderate and vigorous) in healthy adults. At a pre-experimental session, 8 participants (18-30y) residing in a non-fluoridated-area, underwent a VO_{2 max} test to guide the three exercise intensities for the experimental sessions. Participants were on a F-free regime one week before and throughout the four experimental weeks. We measured urinary F excretion (UFE), maximum plasma concentration (Cmax), lag time of Cmax (Tmax), and Area Under the Curve (AUC) for plasma F concentration against time, following F ingestion then no, light, moderate and vigorous exercise. Results showed no statistically significant difference in Tmax among all sessions; whereas Cmax for moderate exercise (226.2 ng/ml) was significantly higher than for no (27.0 ng/ml; p < 0.001), light (105.6 ng/ml; p = 0.016) and vigorous (94.2 ng/ml; p = 0.008) exercise. Mean AUC over 0-90 min following F ingestion was also significantly higher in moderate exercise than for no (p < 0.001), light (p = 0.004) and vigorous (p = 0.001) exercise. Mean UFE over 0-14h was 638.8, 718.7, 574.6 and 450.5  μg for no, light, moderate and vigorous exercise, with no statistically significant differences among different sessions. In conclusion, this human experimental study suggests that moderate exercise may increase the fraction of F absorbed systemically which is therefore available to produce a biological effect. Future studies should be conducted with larger samples, different age groups and using different F doses.