What happens when you take electrolytes with carbohydrates?
The interaction between electrolytes and carbohydrates in a sports-nutrition context is grounded in well-established intestinal physiology. The sodium-glucose cotransporter SGLT1, lining the brush border of the small intestine, moves one glucose molecule and two sodium ions across the gut wall together. Water follows the resulting osmotic gradient, dramatically accelerating fluid absorption compared with plain water or carbohydrate-only solutions. This is the same mechanism that makes oral rehydration solution (ORS) one of the most impactful public-health interventions ever devised: it saves lives in cholera and other dehydrating diarrheal illnesses by exploiting SGLT1 to absorb water faster than the gut can lose it.
For athletes, the practical implication is that a sports drink containing both carbohydrate and sodium delivers fluid to the bloodstream and working muscle faster than water alone, while simultaneously providing exogenous fuel that spares muscle and liver glycogen. The ACSM Position Stand on Exercise and Fluid Replacement (Sawka et al., 2007) codifies this: for exercise lasting longer than about 60 minutes, fluid containing 4-8 percent carbohydrate and 0.5-0.7 g sodium per liter outperforms either water alone or plain carbohydrate solutions for hydration and performance.
Why is this important?
Dehydration of even 2 percent body mass impairs endurance performance, cognitive function, and thermoregulation. Hyponatremia, low blood sodium from drinking too much plain water during long events, is the opposite failure mode and can be fatal in extreme cases (marathons, ultramarathons, prolonged team-sport events in heat). A properly formulated sports drink threads the needle: enough carbohydrate to provide 30-60 g/hour of fuel, enough sodium to support fluid retention and reduce hyponatremia risk, and an osmolality that does not slow gastric emptying or cause GI distress.
For sessions under about 60-75 minutes, plain water is generally adequate for hydration; the carbohydrate-electrolyte advantage starts to matter when glycogen depletion, sodium loss through sweat, and cumulative fluid loss become limiting factors. Heavy sweaters in hot environments, large athletes, or athletes doing very long sessions (over 3 hours) need higher sodium intake than the ACSM minimum to replace what is being lost in sweat.
What should you do?
For endurance exercise lasting 60-180 minutes, target 30-60 g carbohydrate per hour, ideally in a 4-8 percent solution (about 40-80 g carbohydrate per liter), with 300-700 mg sodium per liter. Drink to thirst or follow a 400-800 ml/hour schedule, adjusting for body size, climate, and sweat rate. Practice your hydration strategy in training, not on race day.
For ultra-endurance (over 3 hours), the carbohydrate ceiling can be pushed to 80-90 g/hour by combining glucose (or maltodextrin) with fructose in roughly a 2:1 ratio. Fructose is absorbed via the GLUT5 transporter independently of SGLT1, so the two sugars unlock two parallel absorption pathways and reduce gut saturation. Sodium needs rise too; heavy sweaters may benefit from 700-1000 mg sodium per liter or supplemental salt capsules.
For shorter sessions (under 60 minutes), water alone is fine for most athletes. Adding electrolytes and small amounts of carbohydrate during shorter sessions does not hurt and can support a habit of practiced fueling, but it is not necessary for hydration or performance in that window. People with chronic conditions, heart failure, kidney disease, hypertension, may need to limit sodium intake; consult a clinician about appropriate sodium load during exercise.
Which specific products are affected?
Commercial sports drinks (Gatorade, Powerade, Nuun, Skratch Labs, Maurten, Tailwind) are formulated around these principles, with varying ratios of carbohydrate to electrolytes. Plain electrolyte tablets (LMNT, SaltStick, Liquid IV, DripDrop) contain little or no carbohydrate and are appropriate when you are getting fuel from gels, chews, or whole foods separately. Carbohydrate-only products (gels, chews, sugar candy) lack the sodium component and pair best with water plus separate electrolyte sources.
Hypertonic drinks (over 8 percent carbohydrate, soda, juice, energy drinks) slow gastric emptying and can cause GI distress during exercise; they are fine before or after activity but not optimal during. Hypotonic drinks (below 4 percent carbohydrate) provide hydration but limited fuel. The 4-8 percent range is the well-validated sweet spot for during-exercise use.
The bottom line
Sodium and glucose accelerate intestinal water absorption through the SGLT1 cotransporter, making sodium-plus-carbohydrate fluids the gold standard for endurance hydration over 60 minutes. Target 30-60 g carbohydrate per hour, 300-700 mg sodium per liter, in a 4-8 percent solution. For ultra-endurance, combine glucose and fructose to bypass single-transporter saturation. Below 60-minute sessions, plain water is generally adequate; above that threshold, the electrolyte-carbohydrate pairing meaningfully improves performance and reduces hyponatremia risk.