Olive Oil and Gut Health: What Researchers Are Studying

Many dietary polyphenols, including some of those in olive oil, are not fully absorbed in the small intestine. A proportion reaches the large intestine, where gut bacteria break them down into other compounds.

That is why researchers are interested in them: they want to understand whether and how these compounds, and the bacteria that process them, interact. It is an active and fast-moving field, and the answers are not settled.

Studies in this area have looked at changes in the make-up of gut bacteria and in the compounds they produce when people or animals eat olive oil or olive polyphenols, often as part of a Mediterranean diet.

The limits matter. Many studies are small or short, use different oils, doses and diets, and measure markers in the gut rather than health outcomes. Results do not always agree with each other, and findings in animals or the laboratory may not apply to people. Researchers themselves describe the evidence as emerging.

So it is fair to say the gut is an interesting area of olive oil research. It is not fair to say olive oil has a proven effect on digestion or on any digestive condition, and we do not claim that it does.

The Mediterranean diets studied by researchers are not just olive oil. They are also high in vegetables, fruit, pulses, nuts and wholegrains: foods rich in fibre, which is what UK health guidance emphasises for a healthy gut. The NHS recommends adults aim for 30 g of fibre a day.

Olive oil fits naturally into that kind of eating, dressing vegetables and pulses and replacing butter or other fats in cooking.

Polyphenol content varies widely between oils. It depends on the olive variety, how early the olives were picked, how quickly and how coolly they were pressed, and how the oil has been stored. Refined, "light" and old oils contain very little.

If polyphenol content matters to you, look for an oil that publishes an independent laboratory figure and a recent harvest date. Ours is 410 mg/kg total polyphenols for the 2024/2025 Early harvest, with the full report at castruriali.com/info. We publish it as information about the oil, not as a health claim.

Olive oil is a food, not a treatment. If you have ongoing digestive symptoms, see your GP or a registered dietitian rather than changing your diet on your own. Nothing in this guide is medical advice.