We visited Dr. Lim and staff in Boulder, CO and was a sponge to his wisdom. An excerpt and conversation he shared is below:
Some Notes on High Calorie Maltodextrin Solutions
The comparison between Skratch and high calorie maltodextrin solutions could not be more dramatic. While some companies will tout that their maltodextrin based drinks are better because maltodextrin is a complex carbohydrate rather than a simple sugar, the reality is that a single maltodextrin molecule is simply a manufactured link of anywhere from 2 to 20 simple glucose molecules. In a sense, maltodextrin is like an entire cob of corn, while simple sugars like glucose, sucrose, or fructose are individual kernels. In the end, they are all sugars.
That said there are some important distinctions to be noted. Relative to an all-natural ingredient like cane sugar, maltodextrin is highly processed and derived almost exclusively from GMO corn. Simply put, maltodextrindoes not exist by itself anywhere in nature. And while, in and of itself, “natural” is not always better, in practice some of the worst cases of gastroenteritis, stomach upset, and bloating that I have seen in the last decade of working with professional athletes were completely eliminated when maltodextrin was removed as a fuel source.
The attraction to maltodextrin as a fuel source is that a single molecule or “cob” of maltodextrin contains a higher energy density than a single molecule or “kernel” of glucose, fructose, or sucrose. Thus, per molecule more calories can be dissolved into a given volume of water using maltodextrin than simple sugars.
An important fact about water absorption across the small intestine is that water always moves towards the side of a barrier with the highest number of molecules. The number of molecules in a given solution is measured as that solution’s osmolality or osmotic pressure. This is distinct from the concentration of a solution, which is typically a measure of the mass or weight of the molecules in a solution relative to the volume of water. Accordingly, 10 molecules of maltodextrin containing 20 glucose units each will have the same osmolality as 10 molecules of individual glucose units, despite the fact that those 10 molecules of maltodextrin will have 20 times the calories or a 20 fold carbohydrate concentration.
In theory, what this means is that as long as an ingested solution has an osmolality that is less than blood (260-280 mOsm/L), water will readily move into the body. Based on this, it seems reasonable, that if you want more calories at a lower osmotic pressure, then the rationale choice is maltodextrin.
Unfortunately, what most companies fail to realize is that the osmolality of a maltodextrin solution outside of the body is not the same as it’s osmotic pressure inside the body. As soon as a maltodextrin solution is ingested, enzymes in the mouth, stomach, and small intestine immediately break that maltodextrin down into it’s individual glucose subunits, immediately increasing the osmolality of that solution inside the gut. In effect, those 10 molecules of maltodextrin, explode into 200 molecules of glucose. While a solution with 10 molecules of maltodextrin will have the same osmolality of a solution with 10 molecules of simple sugar outside of the body, inside of the body, the osmotic pressure of the maltodextrin solution can increase by 20 fold causing immediate bloating, gastrointestinal distress, and even diarrhea as water moves from inside the body into the gut – a devastating Trojan Horse scenario. Thus, claims from any company that use maltodextrin as an ingredient that their solution is the same (isotonic) or less (hypotnic) than bodily fluids, are typically unfounded since those measures are either calculated or measured outside of the body. Ultimately, the net result is that most consumers inadvertently pack too many calories into solution when using maltodextrin based solutions, wrongly fearing that they need an excess of calories and ironically creating a massive traffic jam inside of their gut that then prevents them from absorbing more fuel or hydration.
There’s no doubt that carbohydrate usage by endurance athletes can improve performance. The important question to ask, however, is how much carbohydrate? For the vast majority of endurance athletes, the answer is less than you think. In fact, for athletes racing in the Tour de France, when all of the calories (in any form) and all of the water ingested in a typical day is measured, the concentration of carbohydrate is typically 3 to 6% (i.e., 3 to 6 grams per 100 ml of water) depending upon the heat. This is a far cry from the 8 to 12% concentration recommended by most companies selling sports drinks with maltodextrin. If you’re not racing in the Tour de France, your energy needs are likely significantly smaller and while carbohydrate can still be ergogenic, the amount needed to enhance performance is also smaller.
Ultimately, the important question to ask when exercising, especially in the heat, is if you are burning more calories than you’re sweating water and electrolytes, or sweating more water and electrolytes than you’re burning calories. For most people, including every professional athlete I’ve worked with, the answer is that hydration losses are much more rapid than fuel losses. More importantly, the performance declines associated with dehydration are often much more severe if not life threatening than the performance declines associated with fuel limitations. In the same way that we can survive for weeks without food but only days without water, performance declines associated with hydration versus energy are similar.
In the end, I recommend prioritizing hydration using a lower calorie sports drink first. In most cases, not only will your hydration needs be met, so will your energy needs. In those cases, where more calories are needed, real food just works better than high calorie gels and solutions for a few key reasons:
1) It doesn’t all end up in the same place at the same time– There’s a misconception that both solid and liquid calories all end up in the same place. The reality is that solid food gets held up in the stomach where it is digested while liquid food readily bypasses the stomach and rapidly enters the small intestine. Although a rapid influx of calories past the stomach directly into the small intestine might seem appealing at first glance, the problem is that if too many calories enter the small intestine too rapidly, active transport mechanisms in the small intestine may not be able to keep up, causing water to move into the gut because of an unfavorable osmotic gradient. This, of course, can lead to bloating and gastrointestinal distress – the all too familiar gut rot.
2) Normal Digestion is Key to Normal Energy Delivery - Contrary to what many people assume, at exercise intensities below 80% of maximal oxygen consumption, the stomach is well equipped to digest and process food, acting as an important reservoir for calories, regulating it’s entrance into the small intestine so that energy can be better paced into the body. Trying to bypass normal digestion is like trying to get a hundred cars onto a highway at once. The net result is a traffic accident. By allowing normal digestion to occur the stomach acts like a traffic light, metering food onto the highway in an orderly and consistent manner, helping to prevent gut rot.
3) Consistent Energy – One of the reasons the best athletes in the world know that eating solid food early, including a properly timed pre-event meal 2 to 3 hours before their event, is important is because by putting solid food in their stomach early, they can use their stomach as an important energy reserve that allows consistent energy delivery throughout the day rather than sudden spikes that risk gastrointestinal distress.