Drinking Soft Drinks to Quench Thirst May Not be Good for Your Kidneys

• Using a sweetened beverage like a soft drink to rehydrate the body after heat exposure may be harmful to the kidneys.
• Sugars in sweetened drinks worsen dehydration and aggravate pre-existing kidney damage, as revealed by a recent study.
• Water should be the first drink to replenish your body’s water loss due to heat.

In the hot summer months, it is very common for one to return home from the scorching heat and grab a bottle of the favorite soda from the refrigerator to quench thirst. According to a new study published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology reveals that it might not be the best thing to do. In the study conducted on rats, it was observed that sweetened water containing fructose and sucrose in concentrations similar to soft drinks not only worsened dehydration but also aggravated dehydration-induced kidney injury. Dehydration is a common problem, especially in the summer months and has been considered temporary and easily treatable. An increase in the incidence of chronic kidney disease (CKD) in Central America’s sugarcane workers exposed to heat-induced dehydration raised concerns regarding the long-term effects of dehydration on kidney health. This led to a study by Richard J. Johnson and his team which revealed that dehydration caused due to exposure to heat resulted in chronic kidney damage in wild-type mice.

The recent study by Garcia-Arroyo and team has gone a step further and tried to investigate the effect of the type of drink used for rehydration immediately after exposure to heat on the degree of kidney injury. The team comprises of researchers who are inventors on patent applications of drugs to prevent kidney damage by inhibiting fructose metabolism. They are funded by Amway and Danone.

Rats were divided into three groups and exposed to heat stress. The first group was offered plain water, the second was given water containing fructose and sucrose in concentrations (11%) similar to that found in soft drinks, and the third was offered water containing stevia (non-caloric sweetener) for two hours following heat exposure. All the groups were given plain water for the rest of the day. This study was conducted over a period of 4 weeks. An increased oxidative stress and renal inflammation were observed in all groups except the one fed on plain water. This confirmed the association of dehydration with renal injury.

Moreover, the degree of renal injury was the maximum in the group that was fed on the fructose-sucrose water.

The study raises concern on two main issues:

-          The association of dehydration with chronic kidney injury

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There are so many reasons due to which most people are exposed to varying degrees of mild to moderate dehydration like drinking less water due to busy schedules, incontinence issues, and poor habits. If the study is accurate, it means that even mild yet recurrent episodes of dehydration may expose individuals to an increased risk of CKD. Three effects of dehydration may be responsible for the same:

1. Increased secretion of vasopressin (a hormone that promotes water retention and an increase in blood pressure).
2. Activation of the aldose-reductase-fructokinase pathway.
3. Chronic hyperuricemia (increased uric acid in the blood).

-          Carbonated drinks like soft drinks may be harmful to kidney health

There was an increase in intake of water observed in the groups fed on fructose-sucrose water as well as the stevia-containing solution. Despite the increased intake, there was increased kidney damage in the former group.

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The concentration of sugars was similar to that in soft drinks. Though soft drinks have not been tested per se, this study warrants further investigation to determine the correlation.

The authors of the study said, "Our studies raise serious concerns for the common practice, especially among adolescents and young adults, to drink soft drinks as a means to quench thirst following an episode of dehydration.’’

Another interesting observation was the reduction of kidney injury and arterial pressure in the stevia-fed group. A possible theory is the action of stevia as an osmotic diuretic to negate the effects of hypertension induced by dehydration and the resulting kidney injury but it needs to be investigated further for confirmation.

A literature review conducted in the year 2014 analyzed the association of sugar-sweetened soda and chronic kidney disease. Studies that reported odd ratios comparing CKD incidence in patients who consumed sugar-sweetened sodas in significant quantities as compared to those who consumed artificially sweetened sodas were included, a total of five in number. Pooled risk ratios (RR) were calculated. The pooled RR of the group that consumed sugar-sweetened sodas was found to be 1.58 while that of the group which consumed artificially sweetened sodas was 1.33. Thus, the review and meta-analysis of the five studies revealed a statistically significant difference in risk between the two groups in relation to CKD.

The rat study by Garcia-Arroyo reaffirms the association of sugar-containing drinks and kidney injury, albeit in rats.

This makes it pertinent to not only avoid dehydration due to heat in summers as it may cause kidney damage but also choose water over any other drink to rehydrate the body after any exposure to heat stress.

References:

1. You Are What You Drink! Editorial Commentary: Rehydration with Soft Drink-like Beverages Exacerbates Dehydration and Worsens Dehydration-associated Renal Injury
   http://ajpregu.physiology.org/content/early/2016/06/03/ajpregu.00222.2016.full.pdf+html
2. Heat acclimation and thirst in rats
   http://www.ncbi.nlm.nih.gov/pubmed/23439375

Source-Medindia