Beetroot, L-Arginine, and L-Citrulline: Why They Matter for Endurance
Beetroot, L-arginine, and L-citrulline are widely discussed in the endurance community because of their potential to help improve endurance performance by enhancing blood flow, oxygen delivery, and overall cardiovascular efficiency. These supplements are linked to the production of nitric oxide (NO), a molecule that plays a critical role in vasodilation (the widening of blood vessels), which can improve endurance performance.
Here’s why each of these supplements continues to garner attention among endurance athletes.
(1) Nitric Oxide and Blood Flow
Endurance sports require sustained cardiovascular efficiency and consistent oxygen delivery to working muscles. Nitric oxide helps relax blood vessels, which increases blood flow and improves oxygen transport to muscles, delaying fatigue and enhancing endurance performance.
Beetroot is rich in dietary nitrates, which are converted into nitric oxide in the body. Research shows this process can reduce the oxygen cost of exercise, making athletes more efficient at submaximal intensities.
L-arginine and L-citrulline are amino acids involved in nitric oxide production. L-arginine serves as a direct precursor, while L-citrulline is converted into L-arginine in the kidneys, often resulting in a more sustained increase in nitric oxide availability.
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(2) Reducing Fatigue
Endurance athletes are constantly seeking ways to delay the onset of fatigue. By improving oxygen delivery and blood flow, nitric oxide can help reduce muscular fatigue, allowing athletes to maintain performance for longer durations.
Beetroot supplementation has been shown to lower the oxygen cost of exercise and improve time-to-exhaustion during endurance activities.
L-citrulline may also contribute to reduced fatigue and improved recovery by enhancing blood flow and assisting in ammonia clearance, which can accumulate during prolonged exercise and contribute to fatigue.
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(3) Recovery and Performance Enhancement
Beyond endurance performance, recovery plays a major role in an athlete’s ability to train consistently and reduce injury risk.
L-citrulline and L-arginine are often used for their potential to reduce delayed onset muscle soreness (DOMS) and support recovery following intense exercise by improving nutrient delivery and waste removal.
Beetroot and nitric oxide–boosting compounds may also support recovery between training sessions, allowing athletes to maintain higher training quality over time.
(4) Improving Aerobic Efficiency
For endurance athletes such as cyclists, runners, and swimmers, aerobic efficiency is a key determinant of performance. Supplements that reduce the oxygen cost of exercise or improve oxygen delivery can meaningfully impact long-distance performance.
Beetroot supplementation has consistently demonstrated improvements in time-to-exhaustion and exercise efficiency, particularly during endurance efforts lasting several minutes to hours.
L-citrulline may offer similar benefits through nitric oxide–mediated improvements in blood flow, though research in endurance populations is still emerging compared to beetroot-derived nitrates.
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(5) Scientific Interest and Research Support
The endurance community often bases supplement decisions on emerging research. Beetroot, L-arginine, and L-citrulline have been widely studied for their effects on nitric oxide production, oxygen delivery, and endurance performance.
While results vary based on dosage, training status, and sport, the collective evidence has fueled ongoing interest—particularly in beetroot supplementation—as a low-risk, performance-supporting strategy for endurance athletes.
Conclusion
In summary, beetroot, L-arginine, and L-citrulline are popular in the endurance community because they all support nitric oxide production—a key mechanism for improving blood flow, oxygen delivery, and aerobic efficiency. Endurance athletes are drawn to supplements that may reduce fatigue, enhance recovery, and support consistent performance over long durations.
As with all supplements, individual response varies, and these strategies are most effective when layered on top of a well-structured training program and balanced, plant-forward nutrition approach.
If you want to remove the guesswork from training, fueling, and recovery, working with a qualified fitness and nutrition coach can help ensure your strategy aligns with your goals and physiology.
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