After the sport one likes to refresh oneself with a soft drink. Not a good idea, as a New York study showed, because the drinks have been proven to damage the kidneys and lead to prolonged dehydration.
Soft drinks bad for the kidneys
Soft drinks are far from healthy. Often they contain caffeine, flavors as well as sugar, fructose-glucose syrup or sweeteners. Meanwhile, they are co-responsible for the worldwide rising numbers of overweight and diabetics.
Researchers from New York University at Buffalo showed in January 2019 that sweet drinks can also affect kidney health when taken during or after exercise. The study appeared in the American Journal of Physiology.
Soft drinks dehydrate
Previous studies from the 1990s have already shown that exercise – when practiced at high temperatures in summer – increases those blood levels that normally only increase when the kidneys have a problem.
At the same time there were studies (eg from July 2016) in which rats showed that soft drinks with a high fructose content increase the risk of kidney damage if the animals were very thirsty, ie already dehydrated.
The New York researchers now linked these two theses in their study. They wanted to find out how soft drinks – compared to water – changed the renal values of dehydrated athletes during summer training.
Study: How do soft drinks affect sports?
The participants were 12 healthy and athletic adults with a median age of 24 years. They completed a 30-minute treadmill exercise and then did exercises that simulated physical work in agriculture for 15 minutes.
After a 45-minute workout, participants rested for 15 minutes and either received a popular caffeinated and flavored high fructose soft drink or water during that time. All in all, they repeated this one-hour procedure four times, so the participants exercised four times for 45 minutes each and then rested for 15 minutes each. At break there was always the corresponding drink.
A week later the same event took place again, but this time the groups were exchanged. Those athletes who had previously received the soft drink now drank water and vice versa.
Kidney values worsen after soft drink consumption
On the training days, of course, blood samples were taken regularly – in each case before the training, immediately thereafter and also 24 hours later. The creatinine levels and the glomerular filtration rate were tested – both are markers that can detect kidney damage. Heart rate, body temperature, body weight and blood pressure were also checked.
As expected, both kidney-relevant blood levels in the soft drink groups increased. In addition, soft drink users were slightly dehydrated and had higher levels of vasopressin. Vasopression is a hormone that increases blood pressure while ensuring that the body releases as little water as possible from the urine, so that increased vasopressin levels also point to dehydration.
Never drink soft drinks while doing sports or doing physical work!
So, if you think after the summer training that you can supply yourself with soft drinks with liquid, you were wrong. Soft drinks do not rehydrate completely, on the contrary, they leave the body in a dehydrated state.
Of course, these results are not only for athletes who train in the heat, but also for people who (have to) do physical work at high temperatures.
Basically, you should quench your thirst – no matter which group of people you choose – with water. However, especially in the summer or when you sweat a lot, practice a lot or even compete and sometimes drink a lot of water, you should avoid low-mineral water and enrich the water instead with minerals or some sea or rock salt. Occasionally coconut water can also be used as a high quality isotonic thirst quencher.