At a glance:
Olive oil may do more than add flavour to your food. Research has linked virgin and extra virgin olive oil with changes in the bacteria living in our gut, including Bifidobacterium and Adlercreutzia. But while the findings are promising, we still don’t know whether those changes actually translate into better gut health.
Why scientists are looking at olive oil and gut bacteria
The gut microbiome (the trillions of bacteria living in your digestive tract) has become a major focus in nutrition science. Researchers can link gut bacteria to everything from digestion and immunity to mood and metabolic health - and now they’re looking more closely at the foods that might affect the delicate balance of bacteria living there.
That has put olive oil, particularly virgin and extra virgin olive oil (EVOO), under the microscope - quite literally in some cases.
We’ve explored what olive oil polyphenols are, and how they can affect the body in more detail in our other articles - including our guide to high-polyphenol olive oil and our research into olive oil polyphenols and cardiovascular health - but to put it simply, these naturally occurring compounds are one of the reasons researchers are so interested in olive oil’s potential effects.
So, could those same compounds have an effect on the trillions of bacteria living in our gut. And what does the research actually tell us about olive oil for gut health? That’s exactly what we’re going to explore today.
Research notice
Before we look at the studies, it’s worth being upfront about what can and can’t be said. The only authorised UK and EU health claim for olive oil polyphenols relates to the protection of blood lipids from oxidative stress. It doesn’t cover the gut microbiome, digestion, or gut bacteria in any form.
The studies below explore gut-related effects as part of ongoing scientific research. They’re genuinely interesting findings, but they shouldn’t be read as evidence that olive oil or any olive oil product can change, treat or manage gut health.
If you’d like to understand more about the authorised claim itself, our guides to buying high polyphenol olive oil and olive oil and cholesterol cover that in more depth.
What does the latest research actually tell us about olive oil and gut health?
We’ve looked at five recent human studies, each exploring the relationship between olive oil and gut health from a different angle. Each study tells us something useful, but each has its limitations too. Taken together, they give us a better idea of where the evidence is starting to look promising - and where we still need more research.
1. Ni et al. (2026): Virgin olive oil and gut bacterial diversity
Let’s start with one of the largest studies in this group. Published in Microbiome, this Spanish study followed 656 older adults for two years. Everyone was cognitively healthy at the start, although they had overweight, obesity or metabolic syndrome. Researchers looked at how much virgin or common (refined) olive oil they usually ate, alongside stool samples and repeated cognitive testing.
What did they find? People who ate more virgin olive oil had greater gut bacterial diversity at the start of the study, while those eating more common olive oil had lower diversity. The researchers also found a possible link with Adlercreutzia - a type of gut bacteria that can break down polyphenols from food.
There was another interesting finding too: those consuming more virgin olive oil also had better-preserved cognitive function over the two years, while higher common olive oil intake was linked with greater cognitive decline. We’ve looked at the cognitive side of this research in more detail in our article on olive oil and brain health, but here, we’re interested in what the gut might have to do with it.
What does this mean? This is an interesting result, particularly because of the size of the study and its two-year follow-up. But there’s an important catch - this was an observational study, so people weren’t asked to change the olive oil they ate. They reported their usual diets, meaning the study can show an association, but it can’t tell us that virgin olive oil caused the differences in gut bacteria or cognitive function. Other aspects of diet and lifestyle could have played a part too.
2. Correia et al. (2025): Polyphenol-rich EVOO and gut bacteria
Published in Biomolecules, this Portuguese study looked at what happened before and after participants consumed a northern Portuguese EVOO selected for its high polyphenol content. Researchers looked at changes in the bacteria found in the gut and mouth, as well as blood sugar and inflammation.
What did they find? After consuming the EVOO, the researchers found an increase in Bacteroidota, a major group of bacteria, in both the gut and mouth. They also had lower HbA1c, which reflects average blood sugar levels, and lower levels of IL-1β, a marker of inflammation.
How does it compare? Like Ni et al., this study found changes in gut bacteria in people consuming virgin olive oil. But the studies approached the question differently. Ni et al. looked at participants’ usual olive oil intake over two years, while Correia et al. looked at what happened after participants consumed one specific polyphenol-rich EVOO. The Correia study was also much smaller, so while the findings are interesting, they don’t tell us yet whether changes like these translate into better gut health. More research is needed to understand what these changes actually mean.
3. Durán González et al. (2026): EVOO and specific gut bacteria
Published in Life, this Spanish study followed 250 women for six months, including women with fibromyalgia and a smaller group of healthy controls. Participants followed a Mediterranean diet supplemented with either extra virgin olive oil or refined olive oil, allowing researchers to compare the effects of the two oils on the gut microbiome.
What did they find? Overall, the diversity of gut bacteria didn’t change significantly during the six-month study - but that didn’t mean nothing was happening. The EVOO group saw changes in several individual types of bacteria, including Adlercreutzia and a number of bacteria that produce butyrate, a compound linked with a healthy gut microbiome.
How does it compare? This is an interesting contrast with Ni et al., where higher virgin olive oil intake was associated with greater overall gut bacterial diversity. Here, diversity stayed broadly the same, but the researchers still saw changes in certain types of bacteria. And because this was a randomised controlled trial comparing EVOO with refined olive oil, it gives us a useful piece of evidence that the type of olive oil may matter - even when the overall composition of the microbiome doesn’t change. We still can’t say what these individual bacterial changes mean for health, though.
4. Luisi et al. (2019): A Mediterranean diet enriched with high-quality EVOO
This Italian study took a slightly different approach. The researchers asked 18 overweight or obese adults and 18 people of normal weight to follow a Mediterranean diet enriched with 40g of high-quality EVOO each day for three months. They collected stool and blood samples before and after to see what, if anything, changed.
What did they find? In the overweight and obese group, the researchers saw an increase in lactic acid bacteria - a group often associated with a healthy gut microbiome. Interestingly, they didn’t see the same change in the normal-weight group.
How does it compare? This study is interesting because, unlike Ni et al., participants were asked to follow a specific diet rather than simply reporting what they usually ate. But there’s an important limitation: the EVOO was part of a wider Mediterranean diet, so we can’t separate its effects from those of the other foods participants were eating - all those vegetables, fruit and legumes. And with just 36 participants, it’s a relatively small study - all of which means we can’t pin the increase in lactic acid bacteria on the olive oil alone. Intriguing result, but it can’t tell us whether the EVOO was responsible for the change, or what that change might mean for health.
5. Martín-Peláez et al. (2017): Isolating the effect of polyphenol dose
This Spanish study used a particularly controlled approach. Twelve adults with high cholesterol tried three different olive oils over three-week periods, with a break between each one. One was a standard virgin olive oil with a lower phenolic content, while the other two had been enriched with additional phenolics from olive and thyme.
What did they find? The oil with the higher phenolic content led to a significant increase in Bifidobacterium, a type of gut bacteria often associated with a healthy gut microbiome, compared with the lower-phenolic oil.
How does it compare? This is one of the more controlled studies we’ve looked at because every participant tried each of the different oils. That means researchers could compare the changes within the same people, rather than comparing completely different groups. Sounds promising - but there are still some important limitations. With only 12 participants, it was a very small study, and the higher-phenolic oil contained thyme-derived phenolics as well as olive-derived ones. So we can’t say that the change in Bifidobacterium was down to olive oil polyphenols alone.
What does the research tell us so far?
So, what can we say after looking at these five studies? Early research points to some exciting signs that olive oil, particularly virgin and EVOO, may influence the gut microbiome. But it’s not quite as simple as saying it makes the microbiome “healthier”.
The studies vary quite a bit: several were quite small, and some tested EVOO as part of a wider Mediterranean diet rather than on its own - making it difficult to separate the effect of the oil from everything else on the plate.
Interestingly, a 2026 systematic review of 37 studies found much the same. Olive oil was linked with changes in the gut microbiome across the research but with inconsistent results. As always, there’s still a lot more to learn about which parts of olive oil are responsible for these changes, and whether they’ll actually translate into health benefits.
And there’s more research to come. Researchers at the University of Barcelona have already completed a trial comparing a high-polyphenol Corbella EVOO with a lower-polyphenol olive oil, looking closely at how the two affected the gut microbiome. The trial has finished, but so far no results have been published - so watch this space. We’ll be updating this article when the research is published.
Want to explore more of the science behind olive oil? Take a look at our breakdowns of where the current research stands on olive oil and diabetes and high-polyphenol olive oil - or browse our blog for more research and insights.
Frequently Asked Questions
Does olive oil affect gut bacteria?
Research so far suggests that virgin and EVOO may influence the bacteria in our gut, with some studies reporting changes in groups such as Bifidobacterium and Bacteroidota. There are also indications that polyphenol-rich olive oils may have different effects from refined oils. However, the research is still developing, and there are currently no authorised UK or EU health claims linking olive oil with gut health.
Is extra virgin olive oil better for gut health than regular olive oil?
It’s too early to say for certain. Several studies have found more favourable changes in gut bacteria after consuming virgin or extra virgin olive oil (which retain more polyphenols than refined olive oils). But, as we’ve hopefully made clear by now, the research is still developing - so we can’t say that EVOO is definitively better for gut health just yet.
Can olive oil improve digestion?
There isn’t enough evidence yet to say that olive oil improves digestion. Researchers are looking at how olive oil and its polyphenols may interact with the gut microbiome, but we still need more research before this can be considered an established benefit.
What is the best olive oil for gut health?
There isn’t enough evidence to name a “best” olive oil for gut health. Research so far has focused particularly on virgin and extra virgin olive oils, including oils with higher levels of polyphenols - but we don’t yet know whether one type consistently offers greater benefits for the gut microbiome.
Is drinking olive oil good for gut health?
There isn’t enough evidence to say that drinking olive oil improves gut health. The studies we’ve looked at investigated olive oil as part of the diet, rather than drinking it on its own, so we can’t assume that taking a shot of olive oil will have the same effects seen in these studies.
Is EVOO good for gut health?
Research is underway into how EVOO and its naturally occurring polyphenols may interact with the gut microbiome. Some human studies have reported changes in gut bacteria following EVOO consumption, but as we’ve established, there isn’t currently enough evidence to claim any health benefits.
Scientific references
Scientific and nutritional information disclaimer
The information on this website is provided for educational and informational purposes only and summarises published scientific research and general nutritional information relating to olive oil and olive polyphenols. It is not intended as medical, nutritional or dietary advice and should not be relied upon as a substitute for advice from your doctor, registered dietitian or other qualified healthcare professional.
Scientific studies reflect the findings of their respective authors and should not be interpreted as evidence that the same results will occur for every individual or from the consumption of any particular product.
Any health claims made in relation to our products are limited to those expressly authorised under applicable UK and EU nutrition and health claims legislation.
