Why Does Beetroot Improve Cognition in Some Studies but Not Others?

If you search for research on beetroot and the brain, you may notice something confusing.

One study reports better performance on a cognitive task after drinking nitrate-rich beetroot juice. Another finds changes in brain blood-flow responses but no improvement in memory. A longer study gives older adults different doses of beetroot juice and finds no significant effect on cognition at all.

So which one is right?

The answer may be less dramatic than it first appears.

These studies are not necessarily contradicting each other. They often involve different people, different doses, different time periods, different forms of beetroot, and—perhaps most importantly—different ways of measuring cognition.

That distinction matters because a measurable change in the brain does not automatically mean a measurable improvement on every cognitive test.

And that may be one of the most useful ways to understand the current research on beetroot and cognitive function.

Why Have Some Studies Found Cognitive Benefits?

There is a genuine reason researchers became interested in beetroot in the first place.

Dietary nitrate from beetroot can increase the availability of nitrite and nitric oxide, compounds involved in vascular function. Since the brain has a high demand for oxygen and depends on tightly regulated blood flow, researchers have been investigating whether improving vascular function could also influence cognitive performance.

One of the best-known studies was published in 2015.

In that randomized, double-blind study, 40 healthy adults consumed either 450 mL of beetroot juice containing approximately 5.5 mmol of nitrate or a placebo. About 90 minutes later, researchers measured brain haemodynamics while participants completed cognitive tasks.

The beetroot group showed changes in the haemodynamic response in the frontal cortex. More importantly, performance improved on a serial 3s subtraction task. Plasma nitrite also increased, supporting the expected nitrate-to-nitrite pathway.

That study did not show that beetroot suddenly makes people smarter, and it did not show improvement across every aspect of cognition.

But it did provide something important: a human study showing that dietary nitrate could influence both brain physiology and performance on a specific cognitive task.

That was enough to make the question worth investigating further.

Other research has produced similarly interesting signals.

For example, a 14-day pilot trial in 29 overweight or obese middle-aged and older adults compared calorie restriction alone with calorie restriction plus nitrate-rich beetroot juice. The beetroot group showed greater changes in microvascular function and NO-dependent endothelial activity, along with a greater improvement in Trail Making Test B scores. The researchers described the findings as preliminary, and the small sample means they should be interpreted cautiously.

There is also a 2024 randomized crossover trial involving a chewable beetroot-based supplement. After 90 minutes, participants completed a battery of neuropsychological tests. The researchers found improvements in short- and long-term memory consolidation, frontal-lobe functions and cognitive flexibility, while working memory and information-processing speed did not significantly change.

That last result is particularly revealing.

Even when a beetroot-based intervention produces positive findings, it may not improve every type of cognitive performance.

So the question becomes: why don't all studies find the same thing?

Why Have Other Studies Found Little or No Cognitive Benefit?

The strongest answer comes from looking at the research as a whole rather than at one positive study.

A 2019 systematic review and meta-analysis examined randomized clinical trials of inorganic nitrate or nitrite and included 13 trials assessing cognitive function and 9 assessing cerebral blood flow.

Across 297 participants in the cognitive trials, the pooled analysis did not find a significant overall effect on cognitive function. It also did not find a significant overall effect on resting or stimulated cerebral blood flow.

That does not erase the positive studies.

Instead, it tells us that a positive result in one experiment does not necessarily translate into a consistent effect across all populations and testing conditions.

A later study makes the point even more clearly.

In 2022, researchers studied 62 overweight or obese adults aged 60–75 for 13 weeks. Participants received different amounts of nitrate-rich beetroot juice or a nitrate-depleted placebo.

The researchers deliberately tested different nitrate doses, from lower exposure to two 70 mL servings of beetroot juice per day.

After 13 weeks, they found no significant differences in cognitive function or frontal-cortex cerebral blood-flow measures, regardless of nitrate dose.

At first glance, this might seem to conflict directly with the 2015 study.

But look more closely.

The 2015 study asked what might happen after an acute nitrate dose in healthy adults during a specific cognitive task.

The 2022 study asked what might happen after 13 weeks of repeated beetroot juice consumption in older adults with overweight or obesity.

Those are very different experiments.The results do not have to be identical.

Does Better Blood Flow Automatically Mean Better Cognition?

This is probably the most important point to understand.It is tempting to think of the process as a straight line:

More nitric oxide → more blood flow → better cognition.

Human biology rarely works that neatly.

A study may detect a change in cerebral haemodynamics without detecting a change in cognitive performance.

One of the clearest examples comes from a 2024 randomized crossover study of 60 adolescents aged 13–15.

The researchers compared a breakfast containing a beetroot juice nitrate shot with a regular breakfast and no breakfast. Working memory improved in all conditions, but there was no intervention effect on working-memory performance.

At the same time, the nitrate-containing breakfast did change oxygenated-haemoglobin responses in the prefrontal cortex during the working-memory task.

In other words, something measurable changed in the brain, but the participants did not score better because of the nitrate intervention.

That is not necessarily a failed experiment.

It tells us that brain physiology and cognitive performance are related, but they are not the same measurement.

Think about exercise.

Your heart rate can change during a workout without your running time necessarily improving that day. Likewise, a physiological change in cerebral blood flow or haemodynamics does not guarantee that a memory, attention or reaction-time test will improve.

This distinction is easy to miss when research headlines reduce everything to “better brain function.”

Is “Cognition” Actually One Thing?

Not really.

When researchers talk about cognitive function, they may be measuring very different abilities.

For example:

• working memory
• verbal memory
• attention
• processing speed
• executive function
• cognitive flexibility
• reaction time
• mental arithmetic

These are related, but they are not interchangeable.

The 2015 beetroot study found an improvement in a specific serial subtraction task.The 2024 chewable beetroot study found improvements in some memory and frontal-function measures, while finding no significant change in working memory or information-processing speed.

So saying that “beetroot improves cognition” can actually hide an important detail:

Which part of cognition are we talking about?

A supplement might influence one task while having little measurable effect on another.That is why two studies can both be well designed and still produce different-looking results.

Does the Person Taking Beetroot Matter?

The starting point may matter too.

A young, healthy person with relatively good vascular function may have less room for improvement than someone whose vascular function is already compromised.

This is one reason researchers have become interested in older adults and people with cardiometabolic risk factors.

But the evidence does not support a simple rule such as “older people benefit more.”

In fact, the 2022 13-week trial in older overweight and obese adults found no significant cognitive or frontal-cortex CBF benefit despite testing several nitrate doses.

Earlier research in older adults has also described the cognitive evidence as unclear or mixed. A systematic review of nitrate supplementation in older adults found clearer evidence in some physiological and cardiovascular outcomes than in cognitive performance.

So age may be part of the explanation, but it is clearly not the whole explanation.

The same may be true of baseline vascular function, fitness, diet and other characteristics that differ between study populations.

The more accurate conclusion is simply:

The person being studied is part of the experiment.

Does More Nitrate Mean a Bigger Cognitive Effect?

This is another assumption that sounds logical but has not been established.

If nitrate is part of the mechanism, you might expect a higher nitrate dose to produce a stronger cognitive effect.

The 2022 trial was particularly useful because it tested this question directly.

Participants received high, medium or low nitrate exposure from beetroot juice, while another group received nitrate-depleted beetroot juice. After 13 weeks, none of the nitrate doses produced a significant improvement in cognitive function or the measured frontal-cortex blood-flow parameters.

That does not prove that dose never matters.

It simply means that more nitrate should not automatically be translated into more cognitive benefit.

The relationship between nutrition, vascular physiology and cognition is more complicated than increasing one number and expecting the final outcome to rise with it.

This is also why looking only at how many grams of beetroot a product contains can be misleading.

Two products can contain the same amount of beetroot powder while providing different amounts of dietary nitrate.For anyone interested in nitrate specifically, the more useful question is:

How much nitrate is actually being delivered?

Does Beetroot Juice Work the Same Way as Beetroot Powder?

This is where research and everyday shopping can become disconnected.

A large portion of the cognitive research has used nitrate-rich beetroot juice, concentrated beetroot preparations or specific beetroot extracts.

Consumers, meanwhile, may use:

• beetroot powder
• beet juice powder
• liquid concentrates
• capsules
• gummies
• chewable supplements

These products should not automatically be treated as interchangeable.The important point is not that juice is necessarily better than powder.

It is that the form of the product can affect what is actually being delivered.

A study using a standardized nitrate dose is answering a different question from someone taking a teaspoon of an unspecified beetroot powder.

The beetroot itself may be the same plant, but the nitrate concentration, processing method, serving size and formulation can be different.

That is one reason researchers increasingly need standardized interventions if they want to compare results across studies.

A 2025 systematic review of beetroot supplementation reached a similar broader conclusion: physical-performance evidence is considerably more established, while evidence for cognitive improvement remains limited and inconsistent, with a need for more standardized protocols and better dose-response research.

Could Your Oral Microbiome Affect the Response?

There is another part of the story that most consumers probably never think about: your mouth.Dietary nitrate does not simply travel through the body as an isolated ingredient.

The salivary glands concentrate nitrate into saliva, and certain oral bacteria can reduce nitrate to nitrite. That nitrite can then contribute to the body's nitric oxide pathway.

Researchers have found that the composition of the oral microbiome can influence this process.

In one human study, nitrate supplementation changed the salivary microbiome and increased plasma nitrite. Certain nitrate-reducing bacteria were associated with greater increases in nitrite and with changes in nitric oxide-related physiology.

This does not mean that your oral microbiome determines whether beetroot “works” for your brain.

That would be far too strong a conclusion.

But it does show that the nitrate → nitrite → nitric oxide pathway involves more biology than simply swallowing a serving of beetroot.

And that may be another reason why two people consuming similar amounts do not necessarily experience identical responses.

So Why Do Some People Say They Feel Mentally Clearer?

This is where scientific studies and real-world experiences start to look quite different.

Online discussions contain plenty of people who describe beetroot in terms of mental clarity, focus or energy.

In a 2025 Reddit discussion, one user said beetroot powder made their thinking feel noticeably clearer and compared the sensation with the mental sharpness they experience when blood flow increases during cardio.

Another user documented a personal experiment with 30 g of beetroot powder and reported several hours of sustained focus. But they also noted two obvious confounding factors: they had recently been sleeping better and had consumed two cups of coffee instead of their usual one.

More recently, a 2026 Reddit post about “brain fog” described beetroot powder as a major help for the user's perceived symptoms and connected the experience with circulation.

These experiences are interesting.They also illustrate exactly why controlled studies are necessary.

Sleep, caffeine, exercise, expectations, diet, stress and countless other variables can change how mentally sharp someone feels on a particular day.

A person can genuinely feel a difference without being able to identify exactly what caused it.

That does not make the experience meaningless.It simply makes it different from controlled scientific evidence.

So, Why Don't All Beetroot Studies Agree?

Once the studies are viewed together, the apparent contradiction becomes easier to understand.

One study might use a single nitrate dose and test healthy adults 90 minutes later.

Another might give older adults beetroot juice every day for 13 weeks.

Another might measure brain haemodynamics rather than cognitive performance.

Another might use beetroot juice or a chewable beetroot extract.

And the biological response itself can vary between individuals.

Put all of those differences together, and it becomes much harder to expect every study to produce the same result.

The current evidence supports a credible biological connection between dietary nitrate, vascular function and brain physiology. Some human studies have also reported improvements in specific cognitive measures. But the overall evidence does not show that beetroot consistently improves every aspect of cognition in every population.

That is a much more useful conclusion than simply saying that the research is “mixed.”

The better question is not just:

“Does beetroot improve cognition?”

Ask instead:

Who was studied?

How much nitrate was provided?

What form of beetroot was used?

When was cognition tested?

Which part of cognition was measured?

And perhaps most importantly:

Did the study measure a change in brain physiology, a change in cognitive performance, or both?

Those details can completely change how you interpret the result.

For consumers, this also explains why one person may notice clearer thinking after beetroot while another notices nothing obvious.

The science does not currently justify promising a guaranteed cognitive effect. But it does provide a reasonable biological basis for continued interest in beetroot as a nitrate-rich food ingredient—and it gives us a much better framework for understanding why the results are not identical from one study to another.

The interesting part is not that the science gives one simple answer.

It is that the answer may depend on the person, the dose, the timing, the product and the question being asked.