Extra Virgin, Not Refined: What New Gut-Brain Research Reveals About Olive Oil Quality

Not all olive oil is equal, and new research suggests the gap matters more than most people realise. A study published this year in the journal Microbiome, led by researchers at Spain's Universitat Rovira i Virgili using data from the long-running PREDIMED-Plus project, followed 656 adults aged 55 to 75 for two years. Those who consumed extra virgin olive oil showed improved cognitive performance and greater diversity in their gut bacteria. Those who consumed refined olive oil did not — and in some cases, their microbial diversity declined over time.

The lead investigators were direct about what this means. "Not all olive oils have benefits for cognitive function," said researcher Jiaqi Ni. Principal investigator Jordi Salas-Salvadó put it more plainly still: "Quality of fat consumed is as important as quantity; extra virgin olive oil protects the heart and preserves the brain." The distinction, the researchers noted, comes down to processing. Extra virgin oil is extracted mechanically, with nothing stripped away. Refined oil is treated industrially, a process that removes much of the antioxidant and polyphenol content responsible for the effect.

The gut-brain connection

The mechanism the researchers point to is the gut microbiome — specifically a bacterial genus called Adlercreutzia, more abundant among the extra virgin group, which the team links to the cognitive differences observed. It is a reminder that the story of olive oil and the brain runs through the gut, not around it.

This builds on a larger body of evidence. A Harvard T.H. Chan School of Public Health study, published in JAMA Network Open and tracking 92,383 American adults over 28 years through the Nurses' Health Study and Health Professionals Follow-Up Study, found that consuming at least seven grams of olive oil a day — roughly half a tablespoon — was associated with a 28% lower risk of dementia-related death compared with rarely consuming it. "Olive oil contains monounsaturated fats and compounds with antioxidant activity that may play a protective role for the brain," lead researcher Anne-Julie Tessier noted, adding that the association held regardless of the overall quality of a person's diet.

Closer to home, the British Heart Foundation reaches a consistent, careful conclusion: olive oil is rich in monounsaturated fat, "consistently linked with a lower risk of heart disease," and its plant compounds carry antioxidant and anti-inflammatory properties. The BHF is right to caution that a single ingredient is not a substitute for a genuinely varied diet — no oil replaces balance. But taken together with the newer research, the pattern is consistent: what protects the heart tends to protect the brain, and the quality of the oil, not just its presence in the diet, appears to be the deciding factor.

Why this changes how we should think about olive oil

For years, olive oil has been treated as a supporting ingredient — something drizzled at the end of cooking, chosen more for flavour than function. This research argues for a different frame. Extra virgin olive oil, fresh and unrefined, behaves less like a cooking fat and more like a functional food in its own right, one whose benefit is inseparable from its freshness and how it was made.

That is the frame Oliiv was built around. Cold-pressed within hours of harvest, from single-estate groves farmed regeneratively, our oil is bottled with a harvest date so the freshness behind it is never a guess. This is not a technicality. Polyphenol content falls steadily from the moment an olive is pressed, which is why the research above keeps returning to quality and processing, not simply "olive oil" as a category.

A daily ritual, not an occasional flourish

Begin the day with one simple ritual: a spoonful of fresh-pressed olive oil. It is a small, consistent action rather than a single dramatic change — which is precisely how the science suggests these benefits accumulate. The compounds under study, among them:

• Hydroxytyrosol and oleocanthal, polyphenols concentrated in early-harvest, unrefined oil
• Monounsaturated fatty acids, linked by the BHF and others to healthier cardiovascular profiles
• Adlercreutzia and related gut bacteria, associated in the PREDIMED-Plus data with cognitive performance

are not consumed in a single dose. They are built into daily rhythm — a spoonful before breakfast, a generous finish on a plate of vegetables, a small ritual repeated until it no longer feels like a decision at all.

Rooted in provenance

Where the oil comes from is not a footnote to this story; it is the story. A single-origin oil, traceable to one estate and one harvest, gives a clear answer to the question this research keeps raising — was this oil pressed with care, and how long ago? Ours are early-harvest, single-varietal oils from regenerative growers we work with directly, chosen for peppery intensity and polyphenol density rather than shelf life. Vibrant, fresh-pressed, alive — closer, in character, to fruit juice than to a processed cooking oil.

The research keeps arriving at the same quiet point: freshness and quality are not aesthetic preferences, they are the mechanism. A daily ritual built on the right oil is a small thing to ask of a morning, and, on the evidence so far, a meaningful one.

Sources: Ni, J. et al., "Total and different types of olive oil consumption, gut microbiota, and cognitive function changes in older adults," Microbiome (2026), via the PREDIMED-Plus project at Universitat Rovira i Virgili, Spain. Tessier, A-J. et al., Harvard T.H. Chan School of Public Health, "Olive oil may reduce risk of death from dementia," published in JAMA Network Open. British Heart Foundation, "Is olive oil healthy?" This article is for general interest and does not constitute medical advice.