Protein During Exercise: Should You Add Protein to Your Fueling for Ultradistance Events

A Question That Only Emerges in “Ultra” Distances

For most endurance events lasting 1–3 hours, the in-race nutrition consensus is clear: carbohydrates (along with water and electrolytes) are the main focus, and there is no need for protein during the race — adding protein does not provide extra performance benefits and may actually slow gastric emptying and increase gastrointestinal burden. But when events stretch into ultra distances (such as ultramarathons, long-distance triathlons, multi-day races, and ultra-long Gran Fondos), the situation becomes more nuanced, and this is the only scenario where “whether to add protein” is worth serious discussion.

The Potential Role of Protein in Ultra-Endurance Events

Honest conclusion: when carbohydrate intake is already sufficient, most studies show no significant additional benefit from adding protein during the race for “immediate performance.” However, in ultra-long events, situations where carbohydrate intake is difficult to reach sufficient levels, or multi-day consecutive races, small amounts of protein may have auxiliary value in reducing net muscle protein breakdown and aiding day-to-day recovery. Additionally, some ultra-endurance athletes subjectively prefer it (for taste variation, reducing cloying sweetness, and less nausea).

Dosage and Form (If Adopted)

• Adopt a “carbohydrate-first, small protein accent” ratio (carbohydrates remain the energy core; protein is supplementary). A common practical approach is adding small amounts of easily digestible protein (such as hydrolyzed protein or protein-containing energy products) to fueling, rather than large quantities.
• Choose forms that are easily digestible, low-fat, and low-fiber; high-fat, high-fiber protein foods can easily trigger gastrointestinal distress during a race.
• Multi-day events: post-stage recovery fueling (carbohydrate plus protein at approximately 0.3 g/kg) has more robust evidence than “in-race protein supplementation” and should be prioritized (see the protein timing article).

Gastrointestinal Tolerance Is the Deciding Factor

The biggest risk of adding protein during a race is gastrointestinal distress — ultra-long distances inherently involve splanchnic ischemia and a fragile gut (see the articles on gut training and hyponatremia). Any in-race protein strategy must be fully rehearsed during long training rides and simulation races to confirm it does not trigger nausea or bloating; otherwise, it is better not to add it. For those with sensitive stomachs, focusing on carbohydrates plus water and electrolytes during the race and saving protein for post-race recovery is the safer default.

Practical Decision-Making

• Events <3 hours: no in-race protein needed; focus on carbohydrates/water/electrolytes.
• Ultra-long single-day events (ultramarathon/long-distance triathlon): small amounts of protein may be considered to support muscle protection and taste tolerance, but this depends on individual gut testing and is not essential.
• Multi-day events: small amounts during the race may help, but carbohydrate-plus-protein recovery fueling between stages is the priority.

For most races, in-race protein supplementation is an unnecessary burden — carbohydrates are the main focus. Only when the event is long enough that muscle begins to be broken down as fuel, or when racing on consecutive days, does small amounts of protein warrant discussion — and whether you can use it ultimately comes down to a vote cast by your gut during simulation races.

Related Reading

• Protein Needs in Ultramarathons: Muscle Breakdown and Protein Supplementation During Prolonged Exercise
• Protein Intake Timing and Dosage Before, During, and After Cycling: Latest Sports Nutrition Perspectives
• Protein Needs for Endurance Athletes: The Often-Underestimated Intake and Distribution Strategies
• Gastrointestinal Tolerance of Energy-Dense Foods in Ultramarathon Racing: Fueling Research from Trail Running Events