07/26/2026
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With temperatures staying well over 100Ā° and even when it is into the 90sā¦ Drink less sugary and caffeinated products because these is why I actually increase DEHYDRATION SIGNIFICANTLY!
When you start to dehydrate the body portions of the body begin to shut down to protect the more vital areas such as the brain, the heart, the lungs, the kidneys, the liver, all of the internal organs. Double or even triple your water intake, especially before during and after physical activity. But remember, even if youāre sedentary water is massively important!
Several controlled studies (human and animal) link high-sugar + caffeine beverages (especially soft drinks/sodas) to worse dehydration and related harms during or after heat stress/exercise, compared with water. The combination appears more problematic than moderate caffeine alone. Pure caffeineās diuretic effect is often mild and overstated in habitual users, but the high fructose/glucose load in sodas drives osmotic effects, greater fluid shifts, elevated markers of dehydration, and kidney stress under heat load.
Key human studies in heat + exercise
ā¢ Chapman et al. (University at Buffalo, 2019) ā American Journal of Physiology ā Regulatory, Integrative and Comparative Physiology. Twelve healthy adults performed ~4 hours of intermittent exercise (work-rest cycles simulating outdoor labor) in 35 Ā°C heat while consuming either ~2 L of a high-fructose caffeinated soft drink (Mountain Dew-type) or water during the session, plus more afterward. Soft-drink trial produced: higher incidence of Stage 1 acute kidney injury (AKI; 75 % vs 8 % with water), elevated urinary NGAL (kidney-injury biomarker), greater rises in serum uric acid and copeptin (vasopressin marker), larger reductions in estimated GFR, mild dehydration, and higher cardiovascular strain. Conclusion: soft drinks do not rehydrate and elevate AKI biomarkers, likely via vasopressin-related mechanisms.
ā¢ Related 2018 abstract/poster from the same group (Chapman et al., Medicine & Science in Sports & Exercise): Caffeinated soft drink vs water during exercise in 35 Ā°C / 65 % RH. Soft-drink condition raised plasma osmolality, lowered plasma volume more, and increased heart-rate and blood-pressure responsesāindicating worsened dehydration and cardiovascular strainādespite similar core-temperature and body-mass changes.
These findings are frequently cited in discussions of occupational heat stress (e.g., agricultural or industrial work) and potential links to kidney disease risk in hot climates.
Animal evidence (mechanistic support)
ā¢ GarcĆa-Arroyo et al. (2016) ā American Journal of Physiology ā Regulatory, Integrative and Comparative Physiology. Rats underwent recurrent mild heat-induced dehydration (36 Ā°C, 1 h/day) for 4 weeks, then rehydrated for 2 h with plain water, an 11 % fructose-glucose solution matching typical soft-drink composition, or stevia-sweetened water. The fructose-glucose group showed greater dehydration (higher osmolarity and copeptin) despite higher fluid intake, plus worse tubular injury, oxidative stress, and activation of aldose-reductase/fructokinase pathways. Stevia was protective. The authors conclude that soft-drink-like rehydration after heat dehydration worsens both dehydration and renal damage.
Follow-up work from the same group reinforced that fructose rehydration after heat/dehydration accelerates renal inflammation and injury.
Context on caffeine alone vs. sugar + caffeine
Reviews (e.g., Armstrong et al., 2007, Exercise and Sport Sciences Reviews) conclude that moderate caffeine does not meaningfully impair fluid-electrolyte balance, raise core temperature, or reduce heat tolerance in most exercising people; any diuresis is mild and often comparable to water once tolerance develops. Later occupational-medicine summaries (2025) generally view caffeinated beverages as acceptable for hydration in heat, while flagging high-fructose/glucose sodas for theoretical AKI risk (mainly from animal data) and transient hypovolemia from intestinal fluid sequestration.
High sugar content itself can increase thirst and urine output as the body handles the osmotic load, an effect amplified when sweating is already high in heat. Energy drinks or sodas that combine high caffeine plus high sugar therefore pose a dual concern under hot conditions.
Practical takeaway from the literature
Water (or appropriately formulated electrolyte solutions) remains the preferred rehydration choice during prolonged heat exposure or physical work. Soft drinks high in sugar and caffeine do not hydrate as effectively and can elevate markers of dehydration and acute kidney stress. Effects appear most relevant during or immediately after heat + exercise rather than in everyday sedentary conditions. Long-term population risks (e.g., chronic kidney disease in hot-climate workers) remain an active research area.
