Do you need sugar to hydrate? Electrolyte absorption explained

Written by Luis Villaseñor (opens in a new tab)

When my coaching clients ask if they need sugar to hydrate, my short answer is no. Our bodies can absorb sugar and sodium just fine without glucose.

Where does this question about sugar and hydration come from to begin with? Well, glucose can enhance fluid and electrolyte absorption into your body. This likely explains why glucose-based formulas help folks rehydrate from illnessOpens in a new tab. Research also suggests glucose can boost exercise performanceOpens in a new tab, especially in longer endurance events.

But I see a lot of folks conflate this research with the notion that including sugar in their hydration strategy is always better. Any blanket statement like that generally isn’t true, and this case is no exception. Especially since sugar comes with health downsidesOpens in a new tab. As with any health strategy, folks would be better off choosing whether or not to include glucose in their hydration strategy based on their specific needs.

For most people, in most everyday cases, the rule of thumb “drink electrolyte water to thirstOpens in a new tab” will do the trick to keep them hydrated and replace sweat electrolyte losses. No sugar needed. Cases where you may want to consider including glucose in your hydration strategy would be rehydrating during illness or to fuel longer endurance efforts.

Let’s dig deeper into these points. I’ll start with some hydration basics that’ll explain why glucose generally isn’t necessary for hydration. Then I’ll share the research on why glucose may help during illness or exercise.

Hydration Basics

The goal of hydration is to help maintain fluid and electrolyte balance in our bodies. I say “help maintain” because other factors also influence fluid balance, like hormonal health, kidney health, heart health, lifestyle factors, and diet. This proper fluid balance keeps your blood flowing, your skin moist, and your brain floating peacefully in your skull.

Generally, the goal of hydration is to replace the fluids and electrolytes that we lose so that we can maintain our bodies’ fluid balance. Maintaining this balance helps keep our blood flowing, skin moist, and brain floating peacefully in our skulls.

Some of the ways we lose fluids and electrolytes are through sweat, urine, feces, and even breathing. In the simplest terms, this creates an imbalance, we get thirsty or crave saltOpens in a new tab, we drink water or give the salt shaker an extra shake, we absorb these new fluids or electrolytes into our blood stream and cells, and voilà — balance is restored.

Now, let’s see how we absorb fluids and electrolytes, and learn how glucose isn’t the only hydration booster.

Electrolyte Absorption Explained

We can absorb sodium and fluids a number of ways. In fact, it’s worth noting first that sodium and fluids can absorb into your body on their ownOpens in a new tab — they don’t need a boost. For example, a 2014 study found that drinking super salty water (no sugar included) may rehydrate ultra-endurance athletesOpens in a new tab with low sodium levels equivalently to intravenous saline.

While this passive absorption does the job, it’s not the most efficient. Sodium can absorb better when it’s paired with other molecules, including:

Let’s take a closer look at glucose specifically.

How Does Glucose Help With Hydration?

Like the other molecules in the list above, glucose can help our bodies absorb sodium and water better.

Dr. Robert Crane kicked off this discovery in the 1960s — theorizing that glucose helps move water and sodiumOpens in a new tab through the gut and into the bloodstream. Researchers later supported his hypothesis by discovering a protein in the small intestine named sodium-glucose cotransporter 1 (SGLT-1). As the name suggests, SGLT-1 helps transport glucose, sodium, and fluids into your body.

Glucose for illness rehydration

In terms of practical applications, glucose is an ingredient in oral rehydration therapy (ORT), often used to rehydrate patients with diarrhea. The formula the World Health Organization recommendsOpens in a new tab includes 13.5 grams of glucose and 2.6 grams of salt in 1 liter (~34 ounces) of water.

Some researchers estimateOpens in a new tab ORT has saved millions of lives, but it’s hard to say how much glucose (vs. electrolytes or fluids) drove this benefit. Bottom line, though? The evidence suggests ORT is helpful for illness rehydration.

Quick note: glucose is only one type of sugar. Animal evidence suggests another form of sugar called fructose (found in fruit, table sugar, and high-fructose corn syrup) may have a dehydrating effectOpens in a new tab. So consider skipping those soft drinks and fruit juices. They’re fructose bombs.

Let’s move to another potential benefit of using glucose: exercise performance.

Glucose for exercise performance

Our bodies generally like to use sugar for energy, especially when exercising. Consuming sugar/glucose during exercise may improve performance by providing extra energy, especially during longer efforts.

Let’s look at a 2010 Journal of Applied Physiology studyOpens in a new tab for an example. In the study researchers gave 12 cyclists electrolyte waters with varying doses of glucose. Compared to a no-glucose drink, here’s how different doses of glucose improved average power output during a 20-kilometer time trial:

15 grams of glucose per hour: +7.4%
30 grams of glucose per hour: +8.3%
60 grams of glucose per hour: +10.7%

Why did more glucose lead to more power? The study suggests the athletes who consumed glucose burned more glucose for energy during the trial (called carbohydrate oxidation). More energy burned, more power.

What if you want to improve performance without the sugar hit?

One option is to consume a low-carb or ketogenic diet. This way of eating helps folks become fat-adaptedOpens in a new tab, improving their ability to use fat (vs. sugar) for energy. Read Zach Bitter’s storyOpens in a new tab. He broke the American record for the 100-mile race while consuming fewer than 5% of his calories from carbohydrates.

A 2021 meta-analysisOpens in a new tab of 10 studies also found that low-carb interventions didn’t affect aerobic capacity or exercise performance in endurance athletes. This suggests dietary carbs (which digest to glucose) aren’t necessarily a performance enhancer.

I usually don’t use glucose when I exercise, but I see why endurance athletes experiment with it. Weigh the pros and cons of glucose for your situation and experiment as needed. For instance, try adding 10–20 grams of glucose to your electrolyte water. If you feel or note a performance benefit, perhaps keep this protocol. It’s all about what works best for you!

Thinking About Glucose for Hydration

To recap: You don’t need glucose to hydrate, but it may help for illness rehydration or endurance performance.

You can also ask yourself some questions to decide if glucose makes sense for you. Am I rehydrating from an illness? Am I an endurance athlete looking for a performance edge? Am I worried about staying low-carb or keto?

At the end of the day, it’s about what works best for your specific needs and your goals. And you can rest assured that as long as you’re getting enough fluids and electrolytes, hydration can happen just fine on its own — no sugar needed.