Not all carbs are equal in your mouth: amylase differences, endurance, and smarter fuelling

Introduction

Picture two marathoners on the same fuelling plan. Same gels, same carb intake per hour, same training block. One glides through 30 km feeling steady. The other fights a rollercoaster of energy dips and gut niggles. Biology is rarely fair, and one under-appreciated reason sits right where fuelling begins: your saliva. Salivary α-amylase, the enzyme that starts starch digestion in the mouth, varies several-fold between people, and it can change what your body “sees” from the same carbohydrate dose. Understanding this variation gives endurance athletes a cleaner logic for choosing carb forms, timing, and supportive supplements. 

The Problem 

Endurance nutrition advice still treats carbohydrate tolerance and response as mostly about gut training and total grams per hour. Those matter, but they ignore a variable further upstream: how quickly you begin hydrolysing starch before it even reaches the stomach. People differ in both their salivary amylase activity and the number of copies of the AMY1 gene that encodes it. That difference influences the early rise in glucose and insulin after starch, perceptual responses to carbohydrate, and possibly the effectiveness of strategies like carbohydrate mouth rinsing used during hard efforts. Most athletes have never tested, nor even considered, this lever. 

Science deep dive

Salivary α-amylase cleaves α-1,4 bonds in starch, generating smaller dextrins and maltose during chewing and brief oral holding. Individuals vary widely in salivary amylase concentration and activity. A major driver is AMY1 copy number variation: more copies tend to mean higher resting and post-exercise amylase, though copy number explains only part of the variance, with stress, hydration, diurnal rhythms and training also modulating output. 

This variability has metabolic consequences. In controlled feeding studies, people with higher salivary amylase activity show a more rapid early insulin response and a lower subsequent glycaemic excursion after starch. Faster oral hydrolysis seems to “front-load” carbohydrate appearance and signalling, improving overall glycaemic handling for starch-based loads. Mechanistically, that early signal may prime pancreatic insulin and alter gastric and intestinal processing downstream. 

There is also a perceptual and neural angle. High-amylase individuals perceive starch solutions thinning more rapidly in the mouth, an oral marker that carbohydrate is being processed. Separately, carbohydrate sensing in the mouth can engage central reward and motor control centres, improving short-to-moderate endurance performance even when the carbohydrate is not swallowed. The response to mouth rinse appears heterogeneous, plausibly linked to oral carbohydrate sensitivity and, by extension, amylase biology. 

During exercise, salivary amylase can rise acutely, influenced by sympathetic activation. Recent field work confirms activity increases from pre- to post-exercise and shows a positive relation with AMY1 copy number, reinforcing that both genetics and state modulate the enzyme available to start starch hydrolysis during training and racing. 

Two important caveats. First, AMY1 copy number is not destiny. In one cohort, copy number explained roughly 12 percent of amylase protein variation, highlighting large environmental and physiological effects. Second, most performance-specific data are indirect, linking oral carbohydrate signalling to performance, not amylase per se. Still, as a practical biomarker shaping carbohydrate handling, salivary amylase is too useful to ignore. 

Practical application

1. Match carb form to your likely amylase phenotype. If you suspect lower salivary amylase activity, for example, you feel better with simpler sugars than with starch-heavy fuels, or you notice sluggishness after starch-dominant pre-race meals, bias your race fuelling toward rapidly absorbable glucose–fructose mixes and low-osmolality solutions rather than maltodextrin-dominant or starchy foods. Higher-amylase athletes often tolerate starch-forward options better, especially when combined with glucose–fructose blends. 

2. Use an oral phase deliberately. Hold each sip for 5–10 seconds before swallowing during hard efforts of 45–120 minutes, especially early when gut blood flow is constrained. This exploits oral carbohydrate sensing and any amylase-mediated hydrolysis without adding GI load. Mouth rinse alone can help in shorter, high-intensity bouts, but for longer events, rinse-and-swallow is a pragmatic hybrid. Expect inter-individual differences in benefit. 

3. Train the gut, not just the legs. Regardless of amylase status, progressively practise target carb intakes in long runs and rides to upregulate intestinal transporters and improve gastric comfort. Athletes with lower amylase may need more gradual progressions when starch is prominent. 

4. Pre-race meal composition. For lower-amylase phenotypes, lean toward lower-fibre, lower-resistant-starch carbohydrates 2–4 hours pre-start, with a portion of simple sugars and glucose–fructose in the final hour. Higher-amylase athletes can include modest starch portions without the same glycaemic penalty, provided overall fibre is kept sensible pre-race. 

Carb Accelerator is designed with this oral-to-intestinal journey in mind. The formula includes a targeted digestive enzyme blend featuring amylase alongside protease, lipase, plus botanicals such as ginger, fennel and peppermint. For athletes with lower salivary amylase activity, taking Carb Accelerator before carbohydrate feeding can provide enzymatic back-up as the bolus transitions from mouth to stomach, supporting starch breakdown into shorter dextrins that are friendlier for absorption and potentially less provocative for the gut at race intensity. For higher-amylase athletes, it can help maintain consistent carbohydrate processing when stress, dehydration or late-race sympathetic swings otherwise dent digestive efficiency.

In practice, athletes have used Carb Accelerator 15–20 minutes before pre-workout and race meals and again before the first on-course carbohydrate dose to support carbohydrate availability while reducing the risk of GI distress during higher-intensity segments. This is a complement to, not a replacement for, carbohydrate periodisation and gut training. A second contextual mention: pairing Carb Accelerator with a low-osmolality glucose–fructose drink during tempo or threshold work can support sustained energy while keeping gastrointestinal comfort predictable.

Conclusion

Salivary amylase sits at a deceptively powerful choke point in endurance fuelling. Some athletes start turning starch into usable fuel almost immediately; others take longer and feel it in both blood sugar dynamics and gut comfort. The literature supports real, consequential variation in amylase activity and copy number, with meaningful knock-ons for how athletes should choose and use carbohydrates. Layering this knowledge onto your current gut training, and using tools like Carb Accelerator to support carbohydrate breakdown and comfort, is a practical way to make the same grams per hour deliver more stable energy on the road or trail. 

References

1. Mandel AL, Breslin PAS. High endogenous salivary amylase activity is associated with improved glycemic homeostasis following starch ingestion in adults. J Nutr. 2012;142(5):853–858. PMC

2. Carpenter D, et al. Copy number variation of human AMY1 is a minor contributor to variation in salivary amylase protein levels. Hum Genomics. 2017;11:20. BioMed Central

3. Kobayashi Y, et al. Influence of AMY1 gene copy number on salivary amylase activity pre- and post-exercise. Eur J Sport Sci. 2024;24:1–9. PubMed

4. des Gachons CP, et al. Salivary amylase: digestion and metabolic syndrome. Nutrients. 2016;8(12):724. PMC

5. Jeukendrup AE. Carbohydrate mouth rinse: performance effects and mechanisms. Sports Science Exchange. 2013;26(118). Gatorade Sports Science Institute

6. Hartley C, et al. Carbohydrate oral rinsing, cycling performance and complex carbohydrate taste sensitivity. Nutrients. 2024;16(2):296. PMC

7. Farrell M, et al. Effect of AMY1 copy number variation and various doses of starch on postprandial responses. Genes Nutr. 2021;16:19. PMC

8. Yang TJ, et al. Carbohydrate mouth rinses before exercise improve strength and sports performance. Nutrients. 2024;16(8):1248. MDPI