Thank you for this, super helpful and appreciated.
Here's the thing: I can knock off a full IM using isomaltulose (I admit that I was a victim to the marketing) without any GI issue, no bonking and can race super hard. I then go into the desert, start racing when its 40Â°C/104Â°F and after 11 hours (down to about 12Â°C/54Â°F in the night) I'm wrecked: nausea, inability to eat, just fall apart. I can take on fluids that carry electrolytes, but no coke, no sugary drinks, nada; and given that I've got another 12 hours to go, I obviously fail. This was on my second attempt too. Its getting embarrassing.
Looking to drastically redo diet, and so the CHO/SCH rabbit hole led me here. I enjoyed https://doi.org/...7/s00421-020-04534-y
and note with interest this conclusion of theirs (supports your comments):
These findings are supported by Oost- huyse et al. (2015) who reported increased gastrointestinal distress and impaired performance with during-exercise (2 h cycling at 60% VO2max + 16 km time-trial) ingestion of isomaltulose versus glucose/fructose (63 gÂ·hâˆ’1).
Most important point of consideration for you: dehydration compromises gut absorption ability to the extent that you may no longer be able to absorb 50-60g/hr of any carb source, even more easily digestible options. Hence, hydration is supremely important. Therefore, don't use slower carb sources because they may impair your ability to consume adequate sodium and fluid.
Even if you're forced to use lower-than-optimal carb intake rates, it will be better for you to use more rapidly absorbable options (Maltodextrin from Bulk Supplements, via Amazon
+ Fructose from Bulk Supplements on Amazon
, or sugar
or some combo), because they'll allow greater fluid and sodium consumption with less GI distress risk, and thus, better hydration.
Better hydration --â†’ greater ability to absorb more carbs past 10 hours into your event.
Dr. Alex Harrison
PhD Sport Physiology & Performance