Soft Drink Consumption During and Following Exercise in the Heat Elevates Biomarkers of Acute Kidney Injury

ByCrossFitFebruary 19, 2019

This small clinical trial, published by Christopher L. Chapman et al. of the University of Buffalo, considers the impact of soft drink consumption (Mountain Dew) on kidney function during and after activity, specifically simulating the impact of soft drink consumption on physical labor in heat.

Soft drinks already have a bad name as they appear to have a major role in causing obesity, fatty liver and diabetes. However, soft drinks are also dehydrating and should not be used as a hydration drink in any shape or form. Indeed, what we are learning from this recent study is that soft drinks may actually inflict kidney injury in individuals who are dehydrated and have heat stress.

Dr. Richard Johnson, University of Colorado, commenting on "Soft Drink Consumption During and Following Exercise in the Heat Elevates Biomarkers of Acute Kidney Injury"

Subjects completed four one-hour exercise cycles, each 45 minutes on (treadmill-walking at 3 mph at a grade sufficient to achieve 55 percent of max heart rate, followed by lifting tasks) and 15 minutes off, in an environmental chamber set to 95 degrees Fahrenheit and 61 percent relative humidity. These parameters were chosen to simulate the environment of outdoor physical labor. Participants consumed a total of 2 liters in 500 mL doses of beverage over four hours, then an additional liter afterward.

There were no significant differences between groups in terms of heart rate or performance, nor significant differences in hydration levels. However, there were more consistent increases in serum creatinine in the soft drink group compared to controls, with 8/12 in the former group and 1/12 in the latter showing an increase of more than 0.30 mg/dL, which meets a criterion for acute kidney injury (1).

The authors concluded:

“The present study provides evidence … that consuming a soft drink during and following exercise in the heat reduces renal function and increases markers of AKI compared to when consuming water. Specifically, renal function was reduced to a greater extent in the Soft Drink trial, as demonstrated by larger increases in serum creatinine and reduced overnight urine flow rate compared to water. Furthermore, the incidence of stage 1 AKI and overnight urinary NGAL, a marker of renal tube injury, were both higher in the Soft Drink trial. Our data also indicate that elevations in vasopressin (i.e., copeptin) and serum uric acid may play important roles in the mechanisms that lead to the development of AKI evoked by consuming a soft drink during and following exercise in the heat compared to when consuming water.”

Read: Soft Drink Consumption During and Following Exercise in the Heat Elevates Biomarkers of Acute Kidney Injury

 

References

  1. Rahman M, Shad F, and Smith M. Acute Kidney Injury: A Guide to Diagnosis and Management. American Family Physician 86(7): 631-639, 2012.