A while ago, I shared a short post on my Instagram account about how wrong or lack of hydration can slack your performance. Today I want to share which substances your sport drink should contain so you can perform as effectively as possible.
A quick reminder, good hydration works when the fluids go fast into your bloodstream, so your muscles can get fuel and nutrients and get rid of heat and waste they produce while working, as well as when the body can cool itself through sweat.
Swift flow from a bottle to the bloodstream.
The gut, or more precisely the small intestine, absorbs 95% of the fluid we drink. The small intestine's goal is to keep water and sodium in balance which affects if your blood has the right level of osmolality*
*Osmolality shows the concentration of dissolved particles, such as sodium and other electrolytes, in your blood. Higher osmolality means you have more particles in the blood. Lower osmolality means the particles are more diluted.
Normal blood plasma osmolality 275-290 milliosmoles.
To ensure the fluid you drink flows swiftly and efficiently into your bloodstream; it should be of lower osmolality than your blood, ideally 210-260 mOsm.
If blood has a higher osmolality than the fluid you drink, the cells in your small intestine will let that fluid through the intestinal walls to add water to the bloodstream.
On the flip side, if you take in a fluid with a higher osmolality than blood, your intestinal cells will reverse course and pull water from the vascular spaces of your body to dilute the higher osmolality in your gut.
As you might imagine, water running from your muscles to the small intestine is the last thing you need during a workout, which can end in GI distress (bloating, gas, diarrhea and general GI discomfort).
Top-gun-level pilots for optimum hydration.
For optimum hydration, your body relies on fluid cotransporters that carry fluid across your intestinal cells and into the water spaces of the body.
Sodium is the top-gun-level pilot for hydration and works best with a good copilot.
Glucose is sodium copilot. Without glucose, the constant flow of sodium and water into your bloodstream slows down.
That's why plain water isn't optimum for hydration. It doesn't consist of drivers and can cause a volume response - signalling your body to pee out often.
Further, it's known that a mix of sugars is absorbed through the intestinal wall faster than one sugar source. It happens because you can activate more transport mechanisms.
Let's double-click here and learn about the most frequently used in sport drinks and gels: fructose and maltodextrin.
Fructose
Alone, fructose has no benefits because the gut has fewer shuttles with fructose, and fructose takes longer to absorb, which draws water into the gut while the body is trying to dilute what is sitting there.
Therefore, having only fruits before or during workouts is not the best idea. It won't help you become more efficient and can worsen the situation, resulting in a distressed GI (bloating, gas, diarrhea, etc.)
However, fructose blended with glucose has benefits. Many studies demonstrated reduced fatigue and improved exercise performance.
Meanwhile, women should be cautious about fructose consumption, being more responsive to higher amounts than men. Consumption of a high amount of fructose over a prolonged period may lead to changes in fatty acids partition within the liver and accumulation of the liver fat content (PMID: 30205493), as well as regularly upset stomach.
Maltodextrin
It's a high processed carbohydrate which comes in the form of a white powder from rice, corn, wheat, or potato starch.
Many research studies advise that maltodextrin doesn't affect osmolality in the same way as the simple sugars glucose, fructose, or sucrose. Therefore, sport drink producers gladly use this ingredient.
However, Dr Stasy Sims, in her book "Roar", insists that maltodextrin can overload a key "gate" in the small intestines, thus creating the same high osmolality environment in the small intestine as fructose. This eventually ends with undesirable results such as upset stomach and non-delivered fluid to muscles.
I didn't find any research confirming this. Still, I'd not disregard this information knowing that Dr Sims is a leading nutritionist and exercise physiologist who has worked with hundreds of professional athletes. She is a go-to resource on hydration, nutrition, and sex differences. In 2017, she was named one of the top four individuals changing the landscape in triathlon nutrition.
Meanwhile, research studies and articles on maltodextrin, including the article "Sports Drinks on the Edge of a New Era", published in Sport Medicine Report journal in April 2018, suggests that the optimum mix of carbohydrates is maltodextrin and fructose approaching a 1:1 ratio. Further, they add that maltodextrin is preferred over glucose due to the lower osmolality for a given energy density.
Final thoughts.
I intentionally provided different viewpoints on fructose and maltodextrin, willing to show there's no one solution that fits all, and even experts aren't aligned on the best one.
I also can't stress enough that we're all different, and our bodies can react differently to the substances that sport drinks and gels contain. It depends on sex, age, nutrition, recovery routine, our environment, and many other factors.
Eventually, your ultimate goal, being equipped with this knowledge, is to go and experiment in order to build awareness and find the best solution that works for you.
And last but not least, remember that constant diarrhea, gas, bloating and other upset stomach issues are not normal. It's a sign to take a closer look and revise your hydration and overall nutrition.