The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration

Objective: To examine the effect of various combinations of beverages on hy dration status in healthy free-living adult males. Methods: In a counterbalanced, crossover manner, 18 healthy adult males age s 24 to 39, on four separate occasions, consumed water or water plus Varyin g combinations of beverages. Clinical guidelines were used to determine the fluid allowance for each subject. The beverages were carbonated, caffeinat ed caloric and non-caloric colas and coffee. Ten of the 18 subjects consume d water and carbonated, non-caffeinated, citrus soft drink during a fifth t rial. Body weight, urine and blood assays were measured before and after ea ch treatment. Results: Slight body weight loss was observed on all treatments, with an av erage of 0.30% for all treatments. No differences (p>0.05) among treatments were found for body weight changes or any of the biochemical assays. Bioch emical assays conducted on first voids and 24-hour urines included electrol ytes, creatine, osmolality and specific gravity. Blood samples were analyze d for hemoglobin, hematocrit, electrolytes, osmolality, urea nitrogen, crea tinine and protein. Conclusions: This preliminary study found no significant differences in the effect of various combinations of beverages on hydration status of healthy adult males. Advising people to disregard caffeinated beverages as part of the daily fluid intake is not substantiated by the results of this study. The across-treatment weight loss observed, when combined with data on fluid -disease relationships, suggests that optimal fluid intake may be higher th an common recommendations. Further research is needed to confirm these resu lts and to explore optimal fluid intake for healthy individuals.