Olive oil before sugar blunts glucose surge in mice, Kyoto study finds

Giving mice olive oil 15 minutes before glucose slowed gastric emptying and softened the first blood sugar rise, with gut hormones and vagus nerve signalling both involved.

Researchers at Kyoto University have found that giving mice olive oil before sugar appeared to blunt the first surge in blood glucose more effectively than giving the oil afterwards, a result that adds to growing evidence that the order in which foods are eaten can shape how the body handles sugar. The work, published in the journal Diabetes, suggests that nutrient timing may influence a linked response involving the stomach, gut hormones and nerves.

In the experiments, mice were fasted overnight before being assigned to one of three sequences. One group received water followed by glucose, a second received olive oil 15 minutes before glucose, and a third received glucose before olive oil. According to the study, the oil-first sequence slowed gastric emptying, meaning the stomach released its contents more slowly into the small intestine, where glucose is absorbed.

The researchers also found earlier changes in hormone release when olive oil came first. Hormones including glucagon and GLP-1 rose sooner, and other reports on the study said GIP was also involved. GLP-1 helps the body regulate blood sugar after meals, while glucagon is usually associated with raising blood glucose by prompting the liver to release stored fuel. In this case, the team said glucagon appeared to play a part in a broader balancing effect rather than acting alone.

The response was not explained by a single pathway. Blocking either glucagon signalling or GLP-1 signalling alone did not erase the effect, but blocking both weakened it, suggesting the two systems can partly substitute for one another. Experiments that disrupted the vagus nerves, which carry messages between the digestive system and the brain, also indicated that nerve signalling helped shape the result. Importantly, the effect was seen even in mice with type 2 diabetes and in animals with severe insulin deficiency.

That does not mean people should start drinking olive oil before meals as a proven diabetes treatment. The study used mice, not humans, and the test involved glucose after fasting rather than an ordinary mixed meal. Still, the findings help explain why some earlier human work has suggested that eating fat, protein or vegetables before carbohydrates can soften post-meal glucose spikes. The Kyoto team said the next step is to test whether the same food-order strategy produces reliable and lasting benefits in people.