When it’s a hot day and you’re physically active, you’re likely to reach for a refreshing, caffeinated soft drink. Plenty of research tells us that soft drinks are not good for your health. Previous research has also shown that sweetened beverages are linked to a higher risk of kidney disease. Now, a new study from the University at Buffalo in New York shows an association between sugary soft drinks, hot weather and physical activity and how these factors affect the health of your kidneys.
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The researchers studied 12 healthy adults in a laboratory environment where they mimicked working on an agricultural site on a hot day (35 degrees Centigrade). The participants completed one hour of exercise that consisted of a 30-minute treadmill workout followed by three different five-minute lifting, dexterity and sledgehammer swinging activities. After 45 minutes of exercise, the participants rested for 15 minutes in the same room while drinking approximately 473 ml of either a high-fructose, caffeinated soft drink or water. After taking a break, the participants repeated the exercise cycle three more times for a total of four hours. Before leaving the laboratory the participants were given more of their assigned drinks before they could consume any other liquids. The value of their drinks was either one litre or a volume equal to 115 per cent of their body weight lost through sweating — whichever was greater. The researchers measured the core body temperature of the participants. They also measured the participants’ heart rate, blood pressure, body weight and markers of kidney injury before, immediately after and 24 hours after each trial. The participants had both soft drinks and water in trials separated by seven days.
The researchers found that after the soft drink trials, there were higher levels of creatinine in the blood and a lower glomerular filtration rate, both markers for kidney injury. These temporary changes did not occur when the participants drank water. Additionally, the participants’ blood levels of vasopressin — an anti-diuretic hormone that raises blood pressure — was higher and they were mildly dehydrated during and after the soft drink trial.
The research shows that consuming a soft drink during and following exercise in the heat raises the biomarkers of acute kidney injury (AKI) in humans.
Source: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
