If you haven't yet be sure to read our article here about Dextrose. In that article we talk a lot about the basics of sugars we won't repeat here.
What is Maltodextrin
Maltodextrin is a complex carbohydrate that is made from corn, rice or potato starch, however it's molecular chain is shorter than other complex carbs. This allows the maltodextrin to be passed through the stomach into the bloodstream like dextrose\glucose. Before the glucose molecules can be broken down by the cell, the maltodextrin must pass through the liver for the glucose bonds to be broken down. This creates a slower metabolizing process.
Combining Maltodextrin with Dextrose
Gastric emptying, the process of emptying and processing food out of the stomach, is slowed considerably when the osmolarity is raised. Dextrose being a single 6 carbon chain molecule will raise the osmolarity in the stomach slowing digestion. Combining glucose\dextrose with a glucose polymer, like maltodextrin allows for a more even digestion without a slowing taking place.
Thus to get the sugars to hit the bloodstream quickly we mix the dextrose with maltodextrin which helps the dextrose\glucose get through the stomach more evenly and quickly. Allowing our muscles to start eating up the glucose while the maltodextrin heads for the liver to supply a 2nd round of glucose to the muscle. I.E. sustaining the release of fuel.
In Race car terms
Hot rods and race cars will use nitrous in conjunction with race fuel in their cars. Think of glucose as the nitrous, once you hit the go button you get an instance burst of fuel to the engine increasing horse power, while the maltodextrin will allow for more horse power, over standard fuel, but not in such a quick an immediate burst.
When to Avoid Maltodextrin
Very simple, anytime you're not being physically active. Maltodextrin won't provide you any additional health benefits outside of exercise. When you're not on the bike you should focus on whole foods. But when used in the right circumstances maltodextrin can play an important role in our training goals. So when you're on your bike pack a couple brews in that jersey pocket and have an adventure!