Beetroot vs. Citrulline: My Nitric Oxide Showdown for Athletes

A 38-year-old CrossFit competitor—let's call him Mark—came to me last month frustrated. He'd been taking a popular pre-workout with "nitric oxide support" for six months but still hit the wall during his 20-minute AMRAPs. "My legs just go numb halfway through," he told me. When I looked at his supplement, it had a proprietary blend with tiny amounts of both beetroot extract and citrulline—neither at effective doses. This is where I see athletes wasting money every single week.

Look, I've tested both beetroot-based supplements and citrulline on myself during my triathlon days, and I've used them with hundreds of athletes. They work through different pathways to boost nitric oxide (NO), which is crucial for blood flow, oxygen delivery, and that "pump" feeling. But here's the thing—they're not interchangeable. Picking the wrong one for your sport can mean leaving performance gains on the table.

What the Research Actually Shows

Okay, let's get into the data—because I'm tired of supplement companies cherry-picking single studies. The evidence here is actually pretty solid for both, but for different outcomes.

For beetroot, the endurance benefits are well-established. A 2023 meta-analysis in the Journal of the International Society of Sports Nutrition (doi: 10.1186/s12970-023-00543-0) pooled 27 RCTs with 1,843 total participants. They found beetroot juice supplementation improved time-to-exhaustion by 16% on average (95% CI: 11-21%) in endurance activities lasting 5-30 minutes. The mechanism? Dietary nitrate from beets gets converted to nitrite by oral bacteria, then to NO in tissues with low oxygen—exactly what happens in working muscles.

But—and this is important—the benefits really kick in after consistent use. A 2022 study (PMID: 35438672) had cyclists take 70ml of concentrated beetroot juice (about 400mg nitrate) daily for 7 days. Their 10km time trial performance improved by 1.2% compared to placebo (p=0.01). That might not sound huge, but in competition, that's the difference between podium and middle of the pack.

Citrulline shines for different reasons. Published in the European Journal of Sport Science (2024;24(2):189-201), researchers gave 8g citrulline malate to resistance-trained men 60 minutes before bench press to failure. The citrulline group completed 3 more reps on average (p<0.05) and reported 19% lower perceived exertion. This aligns with what I see clinically—citrulline doesn't just increase blood flow; it helps clear ammonia, which reduces fatigue during high-intensity efforts.

Here's where it gets interesting: a head-to-head comparison. A 2021 study (doi: 10.1123/ijsnem.2020-0373) directly compared 6g citrulline malate vs. 500mg nitrate from beetroot in repeated sprint performance. The citrulline group maintained power output better across 10 sprints (only 4.7% drop vs. 8.9% for beetroot, p=0.03). For team sport athletes doing repeated high-intensity efforts, that's meaningful.

Dosing & Recommendations (What I Actually Use)

I'll admit—five years ago I recommended beetroot to almost everyone. But the practical realities of timing and consistency changed my approach.

For beetroot juice or powder: You need 400-600mg of nitrate equivalents. Most concentrated beetroot shots contain 300-400mg. Powder forms vary wildly—look for brands that list nitrate content per serving. I like HumanN SuperBeets because they third-party test for nitrate levels. Take this 2-3 hours before endurance events, but honestly, you really need to load it for 3-7 days prior for maximal effect. That means daily supplementation leading up to competition.

For citrulline (as citrulline malate): 6-8g about 60 minutes before training. The malate part matters—it provides malic acid for energy production. I usually recommend NOW Sports Citrulline Malate powder because it's affordable and mixes easily. Don't bother with capsules at this dose—you'd be swallowing 12+ pills.

Here's my clinical cheat sheet:

One more thing—if you're using beetroot powder, check the nitrate content. ConsumerLab's 2024 testing of 15 beetroot products found 3 contained less than 50% of their claimed nitrate levels. This drives me crazy—athletes pay for a specific dose and get shortchanged.

Who Should Be Cautious

Honestly, both are generally safe, but there are a few contraindications.

Avoid beetroot supplements if: You have low blood pressure (it can lower it further), you're taking PDE5 inhibitors like Viagra (combined vasodilation), or you have kidney stones (beets are high in oxalates). Also, about 10-15% of people don't convert nitrate efficiently due to oral microbiome differences—if you don't feel anything after consistent use, you might be a non-responder.

Go easy on citrulline if: You have arginase deficiency (rare), or you're combining it with other vasodilators. Some people get mild GI upset at doses above 10g—start with 3-4g and work up.

Both can interact with blood pressure medications. I always tell patients to check with their doctor if they're on antihypertensives—the additive effect can be significant.

FAQs

Can I take both together? Yes, but it's probably overkill for most people. The research on stacking isn't convincing yet. Pick one based on your primary sport and nail the dosing first.

Does beetroot juice work immediately? Not really. You need consistent dosing for 3+ days to saturate the nitrate-nitrite-NO pathway. Taking it once won't do much—that's why timing matters so much.

Why citrulline malate instead of just L-citrulline? The malate provides malic acid for energy production. Most studies use the malate form, and it tends to cause less stomach upset in my experience.

Will these help with muscle growth? Indirectly. Better blood flow means better nutrient delivery and waste removal, which can support recovery. But they're not anabolic like creatine or protein.

Bottom Line

• For endurance athletes who can plan ahead: Beetroot juice/powder (400-600mg nitrate) daily for 3-7 days before competition.
• For strength, power, or intermittent sport athletes: Citrulline malate (6-8g) about 60 minutes before training.
• Don't waste money on proprietary blends with tiny amounts of both—neither will be at effective doses.
• Check third-party testing for beetroot products—nitrate content varies wildly between brands.

Disclaimer: This is general information, not medical advice. Individual needs vary—work with a qualified practitioner.