Effect of Exercise on Fluoride Metabolism in Adult Humans

Objective: To measure urinary fluoride excretion (UFE) and plasma fluoride concentration (plasma-F) following no exercise (control) and three exercise conditions.

Methods: In a 4-treatment, 4-period cross-over pilot-trial, 9 healthy volunteers aged 20-35y living in a non-fluoridated area underwent a 2-week “wash-out” with non-fluoridated toothpaste. Prior to each of four different acute conditions separated by one week, with order assigned using a Latin square, participants were given a 1-mg fluoride tablet. The exercise was performed on a stationary bike with the intensity determined by the category-ratio rating scale of perceived exertion (RPE): none (control), light (RPE–3), moderate (RPE–5) and vigorous (RPE-7). Blood and urine samples were taken before (baseline) and after exercise and changes in UFE and plasma-F were measured. Data were analysed using a linear mixed model, adjusting for baseline (pre-exercise) value and any period effect. The mean (95% CI) difference in UFE and plasma-F after each exercise regime was determined.

Results: Mean (SD) age of the participants was 25.3 (3.5) y. Mean baseline-adjusted plasma-F was 8, 10, 15 and 10 ng/ml for control, light, moderate and vigorous exercise, respectively. The effect of moderate exercise vs. control on plasma-F was 7 (-6 to 19) ng/ml. Mean baseline-adjusted UFE was 59, 58, 45 and 48 µg/h for control, light, moderate and vigorous exercise, respectively. Moderate exercise resulted in a lower mean baseline-adjusted UFE in comparison with control (mean difference -14; -2 to -25 µg/h). 

Conclusion: Exercise appears to have no substantial effect on fluoride absorption; however, moderate exercise may reduce fluoride excretion and consequently increase fluoride retention in the body. A larger definitive trial is needed to confirm these findings.