CARBS, CARBS, CARBS

Settle in kids. Time to learn about the sugars you’re putting down and think about the possible pros and cons of each.

Key terms in relation to carb intake:

• Absorption Speed
  How quickly are the sources of carbs absorbed and oxidised for energy?

• Gastric Emptying
  How quickly do the carbs and liquid with it leave your stomach and enter the small intestine?

• Comfort
  For the sake of the exercise in the table, I’m referring to the chance of GI distress.

Discussion points:

• As a new age sensitive gutted man, I use to race on a pure glucose source for the second half of a 70.3 run to get really quick carb oxidation but I rarely took more than 40-50g/hr because for myself, lower carb intake but guaranteed absorption was better for me than a gut shut down trying to absorb more (relatively) complex carb sources. Something to consider if you’re struggling with fuelling on the run.

• If you tolerate fructose well, there is little doubt it’s an advantage in terms of being able to ingest and oxidise more carbs per hour. However, there is a full spectrum of tolerance levels for fructose. If you’re using it for a full Ironman you need to be very confident that you can tolerate it for 7+ hours. Many people can tolerate it for 3-4 hours but not after that. In that instance, I recommend maltodextrin as the primary fuel source for the bike then switch to glucose (likely maltodextrin best - double bonded glucose)/fructose for the run.

• The carb source or amount of carbs might not be your issue with tolerating the amount the type or quantity of carbs. Often, it’s simply that the concentrate is too high. i.e., You’re not drinking enough water to make the osmolality ideal for absorption, given the electrolyte and calorie concentration you’re consuming. Or you’re trying to combine too much electrolytes and carbs together, making the osmolality of the fluid content too high. In which case, you need to decide: do I add more water or reduce the carbs, or reduce the electrolytes to reduce the osmolality of the total package being ingested?

• Your Mum didn’t lie to you. You are special. Your gut is unique, and so is how you tolerate different carbs, and the amounts are also unique. It’s unique but also trainable. Athletes can gradually increase exposure to more carbs or different types of carbs and in many cases, upregulate the enzyme that breaks down that carbohydrate over time. So just because you didn’t tolerate 80g/hr on the run the first time you tried doesn’t mean you’re stuck at 60g/hr for life. Try 65g/hr next time on your key run session. Stick with that for a little while. Then try and edge it slightly higher until you’re confident you’re not getting more carbs per hour.

• The carbs you tolerate