Why you don't need sugar for electrolytes to work

The single most-repeated argument for sugar in sports drinks goes like this: "you need glucose to absorb sodium, because of sodium-glucose co-transport." It sounds clinical and authoritative. It is also, as commonly stated, wrong.

Sodium-glucose co-transport is real. It was a transformative discovery in the 1960s. But its application to a healthy person sipping a hydration drink at their desk is almost the opposite of how it's marketed.

Where SGLT-1 actually came from

The sodium-glucose co-transporter (SGLT-1) was characterised in studies of cholera patients in the 1960s. Cholera causes catastrophic fluid loss; the gut wall stops absorbing water through normal channels. The discovery that adding glucose to a sodium solution restored absorption was, plainly, miraculous — it underpins oral rehydration therapy and is credited with saving tens of millions of lives.

That is the use case where SGLT-1 matters. A damaged gut wall, an emergency, no other absorption pathway available. In that context, the right glucose-to-sodium ratio is genuinely life-saving.

Your gut isn't cholera-damaged

In a healthy gut, sodium has multiple absorption routes — paracellular, sodium-hydrogen exchange, sodium-chloride co-transport. SGLT-1 is one channel among several, and it isn't the rate-limiting step. You don't need glucose for sodium to enter your body. You don't need glucose for water to follow it.

What sugar actually does to a hydration drink

Sugar in a hydration drink does three things, and none of them are "make sodium absorbable."

1. It slows gastric emptying. Concentrated carbohydrate solutions sit in the stomach longer. Pure water leaves the stomach in roughly 10 minutes. A 6% sugar solution can take 20–40 minutes. If you're trying to rehydrate quickly, you've just doubled the time it takes the fluid to even reach your small intestine.

2. It spikes insulin. For a person at rest — desk-bound, on a low-carb diet, or fasted — this is at best unwanted and at worst directly counterproductive.

3. It feeds bacteria. Including the ones in your mouth that don't really need extra fuel.

When sugar genuinely helps

If you're running a marathon, cycling for three hours, or playing two hockey matches back to back, a carbohydrate-electrolyte drink is the right tool. For everything else — gym sessions under an hour, office work, hot days, the school run, fasting — sugar adds friction to hydration without adding benefit.

Why so many products still include it

Sugar masks the salty taste of a properly-dosed electrolyte drink. It also makes the product feel pleasant and reduces buyer hesitation. The result: a category dominated by sweetened drinks that are sold for hydration but engineered for taste.

Repleo is unsweetened with sugar by design. We use a small amount of stevia and natural fruit flavours, balance the salt with citric acid and let the result taste like what it actually is: a clean, slightly tart electrolyte drink that absorbs quickly, doesn't spike insulin, and does its job.