Performance Stack: The Science of Beetroot & Caffeine

Beetroot and caffeine are two of the most researched ergogenic aids in sport. Both are IOC Level A. Both work. But they work through completely different systems.

Beetroot improves oxygen efficiency. Caffeine reduces perceived effort. On paper, stacking them makes sense. In practice, the research is more nuanced.

This guide breaks down what the evidence actually shows — and how to use both without guesswork.

In This Guide

1. How Beetroot Works
2. How Caffeine Works
3. What the Research Says About Stacking
4. The Cardiovascular Interaction
5. How to Stack Them
6. Which One for Which Goal
7. Summary
8. Sources

How Beetroot Works

Beetroot is rich in dietary nitrate. When you consume it, oral bacteria convert nitrate to nitrite. Nitrite enters the bloodstream and is reduced to nitric oxide (NO).

Nitric oxide is a vasodilator. It relaxes blood vessel walls. More oxygen-rich blood reaches working muscles. Your muscles use less oxygen to produce the same power. This is improved oxygen efficiency — a metabolic effect, not a stimulant one.

A robust body of evidence shows beetroot reduces the oxygen cost of exercise and extends time to exhaustion. Benefits are clearest for continuous endurance work. The full matrix of nitrates, betaine, betalains, and polyphenols works together — isolated nitrate salts do not produce the same effect.

Timing: Nitric oxide peaks 2–3 hours after consumption.

Dose: 1 tbsp for standard sessions. 2–3 tbsp for race day or peak blocks.

Key rule: Avoid antibacterial mouthwash. It kills the oral bacteria required for conversion.

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How Caffeine Works

Caffeine is a stimulant. It blocks adenosine receptors in the brain. Adenosine builds up throughout the day and signals fatigue. Caffeine blocks that signal. You don't feel tired because the tiredness signal can't get through.

Here's what matters: caffeine does not produce energy. It masks fatigue. Your body keeps accumulating adenosine underneath the caffeine block. When the caffeine metabolises, the backlog hits at once.

Caffeine also reduces perceived effort and can spare muscle glycogen by increasing fat utilisation.

Timing: Caffeine peaks in the blood 30–60 minutes after consumption.

Dose: 3–6 mg per kg body weight.

Half-life: 3–6 hours. It disrupts sleep quality.

What the Research Says About Stacking

The logic is sound. Beetroot works on the peripheral system (blood flow, oxygen delivery). Caffeine works on the central nervous system (perceived effort, alertness). Different pathways. Potential for additive benefits.

But the performance evidence is genuinely mixed. And that matters.

What individual studies show:

Handzlik et al. (2013) found that beetroot juice co-ingested with caffeine produced 46% higher time-to-exhaustion compared to placebo, and greater improvements than either supplement alone. The authors concluded the combination "likely has additive effects."

Pollex et al. (2025) tested isolated and combined beetroot and caffeine in highly trained kayakers. The result: no effect on 1000m time trial performance for either supplement alone or combined.

Filip-Stachnik et al. (2022) tested the combination in semi-professional soccer players. The result: no significant effect on team-sport-specific performance.

Montalvo-Alonso et al. (2025) tested the combination in resistance-trained males. The result: single and combined beetroot and caffeine increased muscular endurance at 65% 1RM in back squat but not in bench press. The effect was site-specific.

The honest summary: The mechanism is logical. The performance evidence is inconsistent. Some studies show additive benefits. Others show none. The response likely depends on the exercise model, the population, and the doses used.

A separate systematic review and meta-analysis on caffeine and nitrate co-ingestion reached the same conclusion: CAF + nitrates did not offer further benefits on exercise performance from the isolated intake of either.

Part 4: The Cardiovascular Interaction (The Real Story)

This is what the research does support consistently — and it's not about performance.

A 2026 randomized controlled trial by McLellan et al. in Food & Function examined the cardiovascular effects of beetroot and caffeine together. The study found that dietary nitrate supplementation offset caffeine-induced increases in arterial stiffness.

Caffeine alone increased arterial stiffness. Beetroot alone did not. When taken together, the nitrate attenuated caffeine's negative cardiovascular effect.

This is a different kind of benefit. It's not about going faster. It's about protecting cardiovascular function during exercise when caffeine is in the system.

For athletes who use caffeine regularly and want to mitigate its cardiovascular strain, this interaction is meaningful. It supports the logic of stacking — not for performance enhancement, but for cardiovascular protection.