Written by Corrie Pelc — Fact checked by Jill Seladi-Schulman, Ph.D.
Over the last few years, researchers have come to understand that what we eat can have a large impact on our brain health.
Known as the gut-brain axis, this collection of nerves that connect to the digestive system and brain plays a role in regulating mood and behavior, stress levels, and cognitive function. In addition to the nerves, the gut microbiome is also involved in the wellness of the gut-brain axis.
Previous research has linked a dysregulation of the gut-brain axis to irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), inflammatory bowel disease (IBD), chronic fatigue syndrome, multiple sclerosis (MS), Alzheimer’s disease, Parkinson’s disease, and metabolic disorders.
Past studies have found that certain foods can help support the gut-brain axis, such as fermented foods, high-fiber foods, leafy greens, lean proteins, and healthy fats, such as extra-virgin olive oil (EVOO).
Now, a new study published in the journal Microbiome has found that the type of olive oil you use may also matter when it comes to the health of the gut-brain axis.
Virgin vs. refined olive oil
For this study, researchers worked with data from 656 people ages 55 to 75 who participated in the PREDIMED-Plus project. These participants were diagnosed as overweight or obese and with metabolic syndrome. Data were collected over 2 years on the type of olive oil — virgin or refined — participants used, the composition of their gut microbiota, and changes in their cognitive function.
“Olive oil is the main fat source of the Mediterranean diet, which has been consistently associated with better cardiometabolic and cognitive health,” Jordi Salas-Salvadó, MD, PhD, professor in the Department of Biochemistry and Biotechnology at the Universitat Rovira i Virgili (URV) and ICREA Academia in Spain, director of the PREDIMED-Plus Study, and lead author of this study, told Medical News Today.
“However, we still know relatively little about the biological mechanisms behind these benefits. In this study, we wanted to explore whether the gut microbiota could be one of the pathways linking olive oil consumption to cognitive changes over time,” he said.
“At the same time, although different types of olive oil are widely available on the market, an important question arises: are they equally healthy biologically? Are they nutritionally equivalent? There has been very limited research (no research in humans) examining whether these different types may have distinct effects on the gut microbiota and brain health, which is why we aimed to investigate this question in more detail.”
— Jordi Salas-Salvadó, MD, PhD
At the study’s conclusion, researchers found that participants who consumed virgin olive oil rather than refined olive oil showed improved cognitive function and greater diversity in their gut microbiota.
“These findings suggest that the type of olive oil may matter, not only the amount consumed,” Jiaqi Ni, postdoctoral investigator in the Department of Biochemistry and Biotechnology at the Universitat Rovira i Virgili, and first author of this study, explained to MNT.
“Virgin olive oil contains more bioactive compounds, such as polyphenols, which may support a healthier gut microbiota and potentially contribute to better cognitive trajectories. While our results show associations rather than causation, they suggest the importance of food quality in dietary recommendations.”
— Jiaqi Ni
Researchers also observed that consumption of refined olive oil was correlated with a less diverse gut microbiome over time.
“Gut microbiota diversity is often considered a marker of gut and metabolic health,” Salas-Salvadó said. “The lower diversity associated with refined olive oil intake may reflect differences in bioactive compounds compared with virgin olive oil. However, more research is needed to understand how these microbiota changes translate into long-term cognitive outcomes.”
“Future research should confirm these findings in other populations and with longer follow-up,” Ni added. “We also plan to use more detailed microbiome analyses (metagenomesTrusted Source) and metabolomicsTrusted Source to better understand the biological mechanisms linking olive oil, gut microbes, and brain health.”
Showing associations, not proof of cause and effect
MNT spoke with Dung Trinh, MD, internist for the MemorialCare Medical Group and chief medical officer of Healthy Brain Clinic in Irvine, CA, about this study, who commented that he thought the findings were an encouraging piece of research because it connects three areas we increasingly recognize as important for brain health: diet, the gut microbiome, and cognitive function.
“The study suggests that higher consumption of virgin olive oil may be associated with better preservation of cognitive function in older adults, and that some of this effect could be linked to changes in the gut microbiome,” Trinh continued. “At the same time, it’s important to put the findings in context.”
“This type of study shows associations rather than proof of cause and effect. It doesn’t mean that olive oil alone will prevent cognitive decline. But it does reinforce a growing body of evidence that dietary patterns — particularly those rich in plant-based foods and healthy fats like those found in the Mediterranean diet — may support long-term brain health.”
— Dung Trinh, MD
Trinh said for patients concerned about their memory or cognitive health, studies like this are helpful because they highlight practical lifestyle factors that people can control, while the scientific community continues to learn more about how these relationships work.
“Over the past several years, researchers have learned that the gut and brain are connected through what’s called the gut–brain axis,” he explained. “When the microbiome is balanced and diverse, it may promote a healthier environment for the brain. When it’s disrupted, it may contribute to inflammation or metabolic changes that could negatively affect brain function over time.”
Virgin vs. refined olive oil — how can you tell the difference?
When talking about cold-pressed olive oil versus refined olive oil, the biggest difference comes down to processing methods and the preservation of beneficial compounds, said Monique Richard, MS, RDN, LDN, a registered dietitian nutritionist and owner of Nutrition-In-Sight.
“Cold-pressed extra-virgin or virgin olive oil (EVOO, VOO) is mechanically pressed from olives without heat or chemical refining,” Richard explained to MNT. “Therefore, it retains vital compounds such as polyphenols, antioxidants, and vitamins that support anti-inflammatory and neuroprotective effects. ‘Refined’ or ‘regular’ olive oil is often processed with heat and industrial refining, which can remove many beneficial antioxidants during processing.”
When shopping for a quality EVOO, Richard advised looking for:
- “Extra virgin” or “virgin” on the label, often also identified as imported from Italy, Spain, etc., or are you in a region that harvests and produces quality oil locally that you would be able to access or learn more about?
- Dark glass bottles or tins (protects oil from light)
- Harvest date or production date when available
- Single-origin or regionally labeled oils
And she said to avoid:
- Clear plastic bottles
- Oils stored near heat or direct light in stores
When looking to add more EVOO to your diet, Richard said it’s important to emphasize that olive oil works best as part of an overall dietary pattern rich in vegetables, legumes, whole grains, and protein sources such as fish — not as a standalone “superfood.”
She said that some simple ideas of incorporating EVOO into your diet (1-2 tablespoons is plenty) with actual food — sans the TikTok shot trend — include:
- Mixing with herbs and spices or balsamic vinaigrette for a bread dipping oil, or a popcorn topping.
- Using EVOO for salad dressings and vinaigrettes.
- Drizzling over roasted vegetables, whole grains or fruit, and, yes, could even enhance some cake, and desserts.
- Adding to soups, hummus, or dips as a finishing oil, topped with a sprinkle of fresh or dried herbs.
- Using for sautéing vegetables, garlic, or toasting nuts and seeds.
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