If your pre-workout routine leans on a big scoop of caffeine, a new crossover trial suggests your arteries may notice, even when your blood pressure does not. The same study also found that a nitrate-rich beetroot powder taken alongside the caffeine brought those arterial changes back to placebo levels.
The paper, published in Food & Function in 2026 by McLellan and colleagues, is small and short-term. It is still an interesting look at how two of the most popular performance aids interact in the cardiovascular system.
What the Researchers Did
Twenty-four healthy adults (17 males, average age about 24) completed four trials in a randomized, double-blind, placebo-controlled crossover design. Every participant tried every condition, which makes the comparisons cleaner than in a study that splits people into groups.
The four conditions were:
- PL: nitrate-depleted beetroot powder (92 mg nitrate) with no caffeine
- CAF: nitrate-depleted beetroot powder plus 6 mg/kg caffeine
- BR: nitrate-rich beetroot powder (400 mg nitrate) with no caffeine
- BR-CAF: nitrate-rich beetroot powder plus 6 mg/kg caffeine
For a 80 kg person, 6 mg/kg works out to roughly 480 mg of caffeine. That is on the high end of what many pre-workout products deliver, and above what most people get from a single coffee. Researchers measured brachial and central blood pressure and arterial stiffness before and 2.5 hours after supplementation. Macrovascular endothelial function was assessed afterward with flow-mediated dilation (FMD).
The Headline Result: Caffeine Raised Stiffness Markers
Caffeine alone increased two arterial stiffness measures. Augmentation pressure rose by about 3 mmHg, compared with about 1 mmHg on placebo. Augmentation index rose by about 10%, versus about 4% on placebo and about 1% with nitrate-rich beetroot alone. The differences were statistically significant (P between 0.001 and 0.007).
Augmentation pressure and index reflect how much pressure waves bouncing back from the periphery add to the pressure the heart faces. Stiffer arteries return those waves sooner, which increases the load on the heart. Higher values are generally considered less favorable for cardiovascular health.
The Twist: Nitrate Cancelled It Out
When the 400 mg nitrate beetroot powder was taken with caffeine, the rise largely disappeared. Augmentation pressure rose by about 1 mmHg and augmentation index by about 3%, which was statistically indistinguishable from placebo or beetroot alone (P = 0.505-0.689).
Blood tests fit the expected nitrate pathway. Plasma nitrite was higher in both beetroot-rich conditions than in placebo or caffeine alone. Nitrite is a precursor of nitric oxide, which helps blood vessels relax. Interestingly, plasma cyclic GMP, a downstream signaling molecule, did not differ between conditions, so the exact mechanism is not nailed down by this study.
What Did Not Change
It is important not to overstate the findings. Several things stayed flat:
- Brachial blood pressure was not significantly altered by caffeine or beetroot.
- Central blood pressure was likewise unchanged.
- Flow-mediated dilation, a measure of macrovascular endothelial function, showed no differences.
So the headline is not that caffeine spiked blood pressure or damaged vessel lining. The effect was specific to wave-reflection markers of arterial stiffness. That is a subtler signal, and its long-term health meaning is unclear from a single dose.
Practical Takeaways
Nitrate dose: The effective beetroot powder supplied 400 mg of nitrate. Check labels, because beetroot products vary widely and many do not list nitrate content. A product with no stated nitrate amount is a guess.
Timing: Caffeine and nitrate were consumed together, and measurements were taken 2.5 hours later. That roughly matches a pre-workout window, but the study did not test other timings or exercise itself.
Who might care: People who regularly take high-dose caffeine before training, especially those stacking multiple stimulant products, are the most obvious audience. Someone drinking one cup of coffee is far from the 6 mg/kg dose used here.
A sensible approach: If you already use beetroot or nitrate supplements for endurance, pairing them with your caffeine is a low-risk idea based on this data. It is not a reason to raise your caffeine dose.
What We Do Not Know
The limits are substantial:
- One dose, one session. Nothing here speaks to daily use over weeks or years.
- Healthy young adults only. Older people, those with hypertension, or those with existing vascular disease may respond differently.
- No exercise component. The trial measured responses at rest after supplementation, not during or after training.
- Small sample. Twenty-four participants, mostly male, limits generalizability.
- Unclear mechanism. The unchanged cGMP leaves open how nitrate exerted its effect.
- Clinical relevance. Whether a transient bump in augmentation index translates to meaningful risk is unproven.
Bottom Line
This randomized crossover trial suggests that a high pre-workout dose of caffeine can acutely increase arterial stiffness markers, and that 400 mg of dietary nitrate from beetroot powder can offset that increase. Blood pressure and endothelial function were not affected, so there is no cause for alarm. It is an early, mechanistic finding that points to a plausible, food-based way to soften one cardiovascular side effect of heavy caffeine use. Larger and longer trials in more diverse populations, ideally including exercise, are needed before anyone treats beetroot as a protective shield.
