People who consume caffeinated and sugary drinks while working in hot weather may run a higher risk of developing kidney disease, according to new research.
A research team from the University at Buffalo in New York used a laboratory to simulate the working conditions of an agricultural site on a 35°C day. A group of healthy adults were studied as they competed an hour-long exercise cycle consisting of a treadmill workout and lifting, dexterity and sledgehammer swinging exercises.
After 45 minutes of exercise the participants rested for 15 minutes while remaining in the same room. Some participants were assigned 16 ounces of water during this time, while others were assigned 16 ounces of a high-fructose, caffeinated soft drink. This cycle was repeated three more times over the course of four hours. Before leaving the laboratory the participants were given more of their assigned beverage to drink before consuming any other liquids.
Each participant participated in both water and soft drink trials, with each trial separated by at least one week. The researchers measured core body temperature, heart rate, blood pressure, body weight and markers of kidney injury before, immediately after and 24 hours after each study.
Researchers observed higher levels of creatinine in the blood and a lower glomerular filtration rate after the soft drink trials, both of which are markers for kidney injury.
As well as being mildly dehydrated, participants’ blood levels of vasopressin – a hormone that raises blood pressure – were also higher after the soft drink trials.
These changes did not occur in the participants who drank water.
Researchers said the consumption of soft drinks during and following exertion in the heat is simply not rehydrating for the body.
“Thus, consuming soft drinks as a rehydration beverage during exercise in the heat may not be ideal. Further work will need to discern the long-term effects of soft drink consumption during exercise in the heat, and its relation to the risk of [kidney disease].”
Read the full study.