Stavros Kavouras | College of Health Solutions

Since 1944 we know that even mild (

Research data suggest that the state of underhydration and its concomitant increase in plasma vasopressin is associate with a higher risk for diabetes and chronic kidney disease. It is also suggested that increase water intake suppresses vasopressin, resulting in improved glucose regulation, lower risk of urinary tract infections, and kidney stones formation. Additionally, children with concentrated urine seem to improve their cognitive performance by consuming adequate water intake.

Since most of the athletes do not show up to a competition dehydrated (water deficit) but underhydrated (concentrated urine), the important question is whether adequate water intake can improve performance in underhydrated individuals. To our knowledge, there is only one study (published from our group in 2012, Scand J of Sports Medicine) that examined the effect of increased water intake on underhydrated children on exercise performance. We found that increasing the water intake in free-living underhydrated children improved their endurance exercise performance by 12%.

In our recent publication (Suh, British Journal Nutrition), we found that responses to dehydration stimulus might be affected by sex. More specifically, when blood osmolality was raised by intravenous hypertonic saline infusion, women had greater vasopressin responses compared to men, while mood significantly worsened only in women but not in men.

The aim of our proposed study is to examine if increased water intake in underhydrated individuals improves aerobic exercise performance in both women and men. Trained adult subjects will be recruited to participate in a 4-day water intervention program in order to achieve adequate water intake and euhydration. Subjects will classify as euhydrated based on urine osmolality (800 mol/kg). Hydration will be assessed based on urine (osmolality) and blood (plasma osmolality, copeptin, sodium, potassium, plasma volume, and cortisol) at baseline and at the end of the intervention. Exercise performance will be assessed pre- and post-intervention in a cycle ergometer via a validated 5-km test.

Read the final paper from this GSI-funded project here.

Last updated July 2021.