Two natural supplements dominate the conversation around nitric oxide and athletic performance: citrulline vs beetroot powder. Both increase nitric oxide. Both improve blood flow. But they work through different pathways — and they suit different types of athletes.
This guide breaks down the science behind each supplement, compares their effects on endurance and power, and helps you decide which one fits your goals.
What Is Citrulline?
Citrulline is a non-essential amino acid found naturally in watermelon. In the body, it's converted into arginine, which then increases nitric oxide production. Nitric oxide relaxes blood vessels, improving blood flow to working muscles.
Citrulline is popular among strength and power athletes. It supports muscle pumps, nutrient delivery, and the removal of ammonia — a metabolic waste product that accumulates during intense exercise. Research shows it's most effective for short-duration, high-intensity efforts.
What Is Beetroot Powder?
Beetroot powder is made from dehydrated beetroots. It's rich in dietary nitrate, which the body converts into nitric oxide through a different pathway than citrulline. This conversion improves oxygen efficiency — your muscles use less oxygen to produce the same power.
Beetroot also contains betalains (antioxidants unique to beetroot) and betaine (which supports cellular hydration). This full matrix of compounds is why whole-beetroot extract outperforms isolated nitrate salts in performance studies.
A 2009 study in the Journal of Applied Physiology found that dietary nitrate reduced the oxygen cost of exercise by up to 5%. A 2017 systematic review confirmed improvements in time-to-exhaustion of 4–25%.
The Standardisation Problem
Not all beetroot products are equal. Generic powders and juices vary by up to 10x in nitrate content. One scoop might work. The next might do nothing.
Stamox Oxy-Plus is standardised per scoop — full matrix of nitrates, betaine, and betalains. No guesswork. No fluid overload.
Citrulline vs Beetroot: How Each Supports Performance
| Mechanism | Citrulline | Beetroot |
| Nitric oxide pathway | Converted to arginine → NO | Nitrate → nitrite → NO |
| Primary benefit | Blood flow, muscle pumps, ammonia clearance | Oxygen efficiency, endurance, recovery |
| Best for | Strength, power, short high-intensity efforts | Endurance, aerobic events, repeated efforts |
| Antioxidant support | None | Betalains reduce inflammation and soreness |
| Timing | 60–90 minutes pre-exercise | 2–3 hours pre-exercise |
Beetroot Powder vs. Citrulline: Side-by-Side Comparison
| Benefit | Citrulline | Beetroot |
| Endurance | Moderate | Strong — reduces oxygen cost, delays fatigue |
| Power output | Strong — improves blood flow for explosive efforts | Moderate — sustains power across repeated efforts |
| Recovery | Moderate — helps clear ammonia | Strong — betalains reduce DOMS and inflammation |
| Safety | Generally safe | Generally safe; may cause harmless pink urine |
| Research volume | Moderate | Extensive — 180+ clinical studies, IOC Level A |
Which Should You Choose?
Choose citrulline if:
- Your sport demands short, explosive efforts (weightlifting, sprinting, boxing)
- You want acute muscle pumps and improved blood flow
- You train at maximum intensity for brief periods
Choose beetroot if:
- Your sport demands sustained endurance (cycling, running, triathlon, rowing)
- You want improved oxygen efficiency and delayed fatigue
- You want faster recovery between sessions
- You want a supplement backed by 180+ studies and classified as IOC Level A
You can take both. Citrulline and beetroot work through different nitric oxide pathways. They can be stacked — citrulline 60–90 minutes pre-exercise, beetroot 2–3 hours pre-exercise.
"With Stamox I found really better recovery, something I didn't have before. I had feelings of ease and oxygenation I'd never experienced."
— Filippo Pellegrini, Runner
Get the Free 28-Day Oxygen Efficiency Protocol →
Citrulline vs Beetroot: Frequently Asked Questions
Can I take citrulline and beetroot together?
Yes. They work through different pathways and can be stacked. Space them apart: citrulline 60–90 minutes before exercise, beetroot 2–3 hours before.
Which is better for endurance?
Beetroot. Its primary mechanism is improving oxygen efficiency, which directly translates to better endurance and delayed fatigue. Citrulline supports blood flow but doesn't reduce the oxygen cost of exercise.
Which is better for muscle pumps?
Citrulline. It's widely used for acute vasodilation and muscle pumps during resistance training.
Is beetroot or citrulline safer?
Both are generally safe when used as directed. Beetroot may cause harmless pink urine due to natural betalain pigments.
Further Reading
- Best Time to Drink Beetroot Juice → — The 2–3 hour golden window, loading protocols, and the mouthwash rule.
- 7 Benefits of Beetroot Juice in the Morning → — Steady energy, sharper focus, and better blood flow.
- The Science Behind Beetroot & Baking Soda → — How to stack two ergogenic aids for combined performance benefits.
Sources & Further Reading
- Bailey, S.J., et al. (2009). Dietary nitrate supplementation reduces the O₂ cost of exercise. J Appl Physiol, 107(4), 1144-1155.
- Domínguez, R., et al. (2017). Effects of Beetroot Juice Supplementation on Cardiorespiratory Endurance. Nutrients, 9(1), 43.
- Ochiai, M., et al. (2012). Short-term effects of L-citrulline supplementation on arterial stiffness. Int J Cardiol, 155(2), 257-261.
- Jones, A.M. (2014). Dietary nitrate supplementation and exercise performance. Sports Med, 44(Suppl 1), 35-45.
How We Source Our Information
Every claim on this blog is backed by peer-reviewed research and Stamox R&D data. We cite studies from PubMed, the International Olympic Committee's consensus statements, and the Australian Institute of Sport's supplement framework.
This article was last reviewed on June 2026.
