For most of the last two decades, the endurance nutrition world has operated on a simple rule: 90 grams of carbohydrate per hour is the ceiling. Push beyond that and you risk GI distress, bloating, and a performance-killing pit stop. For many athletes, this ceiling has become gospel.

But the science — like most things in sports nutrition — is more nuanced than a single number. And recent research is making a compelling case that gut-trained athletes using the right formula can go meaningfully beyond 90g/hr.

How the 90g/hr Number Was Established

The 90g/hr figure comes primarily from the foundational work of sports scientist Asker Jeukendrup and colleagues, published through the early to mid-2000s. The key insight was this: glucose, ingested alone, saturates its intestinal transporter (SGLT1) at around 60g/hr. No matter how much more glucose you consume, your gut simply can't absorb it any faster.

But fructose uses a different transporter — GLUT5. By combining glucose and fructose, you effectively open a second absorption lane, allowing total carbohydrate oxidation to climb to approximately 90g/hr. This was a major finding, and it underpins the dual-carb formulas used by elite athletes and consumer nutrition brands alike — including Penny Performance.

"When multiple transportable carbohydrates are ingested, oxidation rates can increase significantly — up to 105 g/hr — compared to glucose alone." — Jeukendrup, 2014

The New Ceiling: 120g/hr

In 2022, Tim Podlogar and colleagues published a study that pushed the conversation further. Participants ingested fructose-maltodextrin mixtures at both 90g/hr and 120g/hr, and the results were striking: the higher intake did produce meaningfully greater exogenous carbohydrate oxidation. The body was absorbing and burning more fuel.

Critically, the extra carbs at 120g/hr appeared to increase oxidation rather than simply blunting fat burning — though this distinction is still an active area of research. The practical implication is clear: for athletes who have trained their gut, there is real physiological headroom above 90g/hr.

What "Gut Training" Actually Means

The caveat in all high-carb research is consistent: gut training matters. Your intestinal transporters are adaptable. Athletes who regularly practice consuming carbohydrates during training — gradually increasing volume over weeks — develop a higher tolerance for fast carb absorption with less GI distress.

This isn't just anecdotal. A 2011 study by Jeukendrup and colleagues showed that trained athletes who practiced high-carb fueling during exercise upregulated intestinal SGLT1 expression — literally making their gut more efficient at absorbing glucose. The same adaptation appears possible for GLUT5 and fructose handling.

What This Means for Penny Performance Athletes

Our formula uses a 1:0.8 glucose-to-fructose ratio, which Podlogar's research specifically identifies as appropriate for high-intake scenarios. Combined with the clean, filler-free ingredient list that keeps your gut from processing unnecessary load, Penny Performance is designed to support athletes working toward the upper range of carb absorption.

For most athletes, 60–90g/hr remains the practical target. But for those training seriously — preparing for ultramarathons, long-course triathlons, or multi-day events — building toward 120g/hr with gut training is a scientifically supported goal. And at Penny Performance's price point, the economics of testing and iterating your fueling strategy actually make sense.

"We cut the marketing budget, not the formula." — Penny Performance

Our Recommendation

Start at 60g/hr if you're new to carb fueling. Work toward 90g/hr over 4–8 weeks of consistent training-day practice. If you're preparing for events lasting over 3 hours, consider gradually building toward 90–120g/hr over a full training season — using our fueling calculator to dial in the right combination of Drink Mix and Gel servings.