Mix Your Own Sports Drink and Minimize GI Distress

As it turns out, it’s really easy to mix your own sports drink with readily available ingredients.

And by understanding a really simple chemistry principle, you’ll be able to mix your own sports drink and tailor it to your specific nutritional needs while minimizing gut issues during a run (bloating, cramps, diarrhea, etc.).

It also explains why some sports drinks, gels, and even different flavors from the same company lead to GI distress while other brands/flavors don’t.

It’s SOOOO fascinating! ?

Let’s start with the base recipe and build our knowledge and understanding from there.

Start With This Recipe

This recipe closely mirrors the caloric, carb, and sodium content of Tailwind, Skratch Labs, and Gatorade Endurance powders (i.e. most sports drinks).

It’s subtly sweet with some lemony tartness.

Recipe	Nutrition Facts
12oz water 16g maltodextrin 10g fructose 1.5g sodium citrate 2–3 lemon packets	99 calories 25g carbs 350mg sodium

The links take you to the products I’m using (all available on Amazon). If you need a kitchen scale, here’s the one I have.

Outside the United States? If Amazon in your country doesn’t have the same product, search for equivalents using these terms: maltodextrin powder, fructose powder, sodium citrate, or citric acid.

Ideally, you won’t have any gut issues with the recipe above since it’s relatively conservative. If anything, your stomach might tolerate it better than other sports drinks because it has less junk ingredients (that could lead to GI distress).

Start with this recipe and try it on a run. If it meets your nutritional needs, doesn’t jack with your stomach, and tastes good (enough), then let’s hit the #easy button and call it a day.

Feel free to stop reading now.

However, if you want to adjust the recipe, whether that’s to increase the amount of carbs, sodium, or tweak the sweetness/taste, you definitely want to keep reading.

You can’t just change the carbs, sodium, and flavoring willy nilly.

There’s some science involved with choosing the right ratios for each ingredient to minimize GI distress.

Before You Change the Recipe, Know This

Let’s talk about tonicity.

It’s the key chemistry principle to understand when mixing your own sports drink for running (or other endurance sports).

In a nutshell, a sports drink is either less concentrated (hypotonic), more concentrated (hypertonic), or similar in concentration (isotonic) to the concentration of salt and sugars in blood.

This is determined by comparing a sports drink’s osmolarity to the typical range for blood.

Tonicity	Good For	Concentration	Osmolarity
Hypotonic	Hydration over nutrition	Lower than blood	< 275
Hypertonic	Nutrition over hydration	Higher than blood	> 295
Isotonic	Hydration and nutrition	Similar to blood	275–295

Note: If you go further down this rabbit hole yourself, you might see references to osmolality. While slightly different, osmolarity and osmolality are interchangeable in this context (since the values are within 0.5% of each other).

The tonicity determines what a sports drink is good for.

Hypotonic

Hypotonic drinks get absorbed by the body the quickest which is why they’re great for hydration. The downside is they contain less carbs per serving than isotonic or hypertonic drinks, so they’re not going to provide enough energy for longer duration activities.

Mix hypotonic drinks when hydration is the priority over nutrition. For example, light to moderate intensity running under 90 minutes.

Because the drink is less concentrated than blood, water gets pulled from the drink and sent to the bloodstream until the drink’s tonicity balances the blood’s.

This is how a hypotonic drink rehydrates the body so well.

Hypertonic

The opposite is true for hypertonic drinks.

They can deliver a lot of carbs and energy at the expense of hydration and slower absorption rates (compared to hypotonic and isotonic sports drinks). Most recovery drinks are hypertonic because they provide a lot of calories, carbs, and/or protein more efficiently than eating solid foods with the same nutritional content.

Mix hypertonic drinks when nutrition is the priority over hydration (and your body isn’t being strained). For example, after a run or to pre-load carbs or sodium the days before a race or long run.

During a run, hypertonic drinks should be avoided at all costs. Unless you’re a fan of GI distress. ?

When a drink is hypertonic, it’s more concentrated than blood. To dilute it so that it matches the tonicity of blood, the body pulls water from the bloodstream.

This is why hypertonic drinks (sodas, alcohol, or fruit juices) never seem to quench thirst because they’re actually dehydrating your body.

Isotonic

When it comes to hydration and nutrition, isotonic drinks hit the sweet spot for runners—providing carbs and hydration in one gulp.

They’re ideal for moderate-to-higher intensity runs over 90 minutes. It’s why most sports drinks are isotonic.

Hopefully you now understand the importance of tonicity (and osmolarity) and why you can’t just throw ingredients together.

You might unintentionally create a hypertonic drink which isn’t suitable during a run.

And this explains why certain flavors within the same brand can cause GI distress but not others. The more ingredients you add to a sports drink (i.e. fancy flavors), the higher the tonicity. Based on studies, some flavors of sports drinks (and I imagine gels, too) are actually hypertonic which would explain why certain flavors don’t sit well with the stomach! ?

It’s also why lemon and citrus flavors are really popular. They’re able to add flavor with less impact on tonicity compared to more complex flavors.

Now, back to the original reason you’re reading this section: you want to tweak the recipe.

But how do you change the recipe and ensure the drink is hypotonic or isotonic?

You use a fan dangled calculator I created.

Big thanks to my brother-in-law for helping me dial in the calculations. (His PhD in soil science was worth it just for this!)

Calculating Tonicity

It’s so fancy it gets its own page. ?

Why These Ingredients

When you look at the research and boil it down, a sports drink really only needs three ingredients:

1. Maltodextrin (a source of carbs)
2. Fructose (a strategic second source of carbs)
3. Sodium (the only electrolyte that needs replenishing)

The carbs are for energy and the sodium to keep your muscles firing.

Flavoring, vitamins, or other electrolytes aren’t necessary and actually reduce the effectiveness of the drink (i.e. delivering the most carbs and sodium as efficiently as possible).

Let’s take a look at each ingredient and why it matters.

Maltodextrin

While you may not be familiar with maltodextrin, you’ve definitely eaten some. It’s used in a variety of foods like soda, beer, dietary supplements, candy, and most sports drinks/gels.

Maltodextrin is easily the star ingredient and rightfully so because:

• It’s efficient at delivering a high number of calories and carbs per gram.
• Is easily digestible (reduces GI distress).
• Is relatively tasteless. At least the type we’ll use.
• Has a minimal impact on tonicity (compared to fructose).

While it’s considered a complex carbohydrate, it actually functions like a simple carbohydrate because it breaks down into glucose—a simple sugar easily processed by the body.

And a critical source of energy.

In energy metabolism, glucose is the most important source of energy in all organisms.

Wikipedia

As a runner, this should be your new favorite ingredient. It deserves to be in the G.O.A.T. conversation.

One thing to note about maltodextrin is that it’s classified by its dextrose equivalent (DE)—ranging from 3 to 20. Maltodextrin is made up of varying length glucose chains. The shorter the glucose chain, the higher the DE, the higher the sweetness, and the easier it mixes in water.

For sports drinks, it seems maltodextrin with a DE of 10 is the most common. Probably because it does a good job balancing sweetness/taste (minimal) with solubility (dissolving easily in water).

Fructose

If maltodextrin is the star of the show, fructose wins for best supporting actor. There’s a few main reasons for adding fructose to a sports drink:

• You need more than 60g of carbs per hour.
• Helps reduce GI distress (in combination with glucose).
• Sweetens the drink without adding non-essential ingredients.

The first two points being the most important.

The body can only absorb up to 60g of carbs per hour from glucose alone (maltodextrin). But studies show a combination of glucose and fructose not only increases how quickly carbs are absorbed but also the total amount that can be absorbed (up to 90g per hour).

This is because the body absorbs glucose and fructose differently. So while your body is processing glucose it can also process fructose at the same time.

Basically, you have two “energy highways” working side-by-side instead of one.

If you’re running less than two hours, you probably don’t need more than 60g of carbs per hour. However, you will once you start running longer than that.

Now, as much as fructose deserves a best supporting actor nod, there is one big downside: it has a much higher impact on tonicity than glucose.That means you’re not able to cram as many carbs from fructose into a sports drink as you would from maltodextrin.

Sodium Citrate

While you could easily use regular table salt, there are a couple benefits to using sodium citrate instead:

1. In combination with glucose, it increases sodium absorption better than sodium chloride (table salt).
2. Has a 30% lower impact on tonicity.

You’ll also notice sodium is the only electrolyte I’m replacing in my sports drink mix. Studies show sodium is the only electrolyte that needs to be supplemented when running.

All the other electrolytes are lost in such small quantities that it doesn’t matter.

Flavoring

Realistically, flavoring is optional. Because fructose is naturally sweet, any drink including it will have a mild sweetness to it.

The sweetness from fructose and neutral taste of maltodextrin make the drink surprisingly palatable on its own (think watered down sugar water). If I really wanted to, I could train my taste buds to drink it as-is. However, the better tasting you can make a sports drink, the more likely you are to drink it during a run (and get the necessary hydration and nutrition).

So wanted to see if I could improve the taste a bit.

Flavoring can come from a lot of different things: Crystal Light, Kool-Aid, fruit juice, flavored syrups, etc.

However, doing so makes calculating tonicity much harder (because of ingredients in unknown quantities). That’s why I wanted flavoring using the simplest ingredients possible.

That’s how I landed on lemon crystals (essentially just citric acid).

It adds some tartness which makes the drink actually taste more like a sports drink than sugar water.

Things to Improve

I feel what I’ve got here is a solid starting point. However, there are some things I’d still like to do.

• Add scientific references. I read a bunch of research but want to only include the ones that have been highly vetted.
• Look for other sources of fructose that could improve the fructose to glucose ratio with minimal impact on tonicity.
• Find other ingredients for flavoring that still make it easy to estimate tonicity.
• Nail down two recipes. One with less than 60g of carbs per hour and another with more carbs for longer duration runs.
• Within reason, confirm the accuracy of the osmolarity calculations. My brother-in-law has a plan to do just that!

If you have questions, let me know in the comments. Especially if you try or tweak the recipe. I’d love to hear the recipe you end up using.