Consuming Olive Oil First May Soften Blood Sugar Spikes, Mouse Study Finds

Olive Oil Slowed the Stomach and Softened Early Blood Sugar Spikes in Mice

Olive oil proved a better meal opener than closer for mice. Given 15 minutes before glucose, a simple carbohydrate, it blunted the early blood sugar surge that followed; given afterward, it did not help. The trick worked in animals whose insulin-producing cells were badly damaged, pointing to something simple: the order in which foods are eaten.

After a carb-heavy meal, blood sugar climbs fast, and taming that climb is a key goal of diabetes treatment. The condition affected more than 580 million people worldwide in 2025, according to figures cited in the paper. Eating vegetables, protein, or fat before carbohydrates has been linked to smaller spikes. Meal sequencing is appealing, corresponding author Daisuke Yabe of Kyoto University said in a press release, because it “merely changes how a meal is eaten” instead of asking people to give up whole food groups.

Scientists had not pinned down why the order matters. A team from Gifu University and Kyoto University, working with colleagues in Canada, Australia, and Germany, went looking for the body’s wiring and published the work in the journal Diabetes.

Olive Oil Given First Shrank Early Blood Sugar Spikes

Main experiments used 8-week-old male mice, five to six per group. After an overnight fast, one group got olive oil 15 minutes before a glucose solution, another got it 15 minutes after, and a third got plain water first for comparison. All three groups then received the same glucose dose. The oil dose was 5 milliliters per kilogram of body weight, a hefty fat dose for a mouse, by the authors’ account. Blood draws over the next two hours tracked blood sugar, insulin, and several digestion hormones. A separate test followed acetaminophen, a common pain reliever, through the bloodstream to show how fast the stomach emptied.

Mice that got oil first had significantly lower blood sugar 15 and 30 minutes after the glucose and emptied their stomachs more slowly than the other groups. That pace matters because the stomach decides how quickly glucose reaches the intestines and then the blood. Insulin stayed about the same in all three groups, but digestion hormones rose more sharply when oil came first.

That benefit was early, though. Total blood sugar across the full two hours did not differ significantly between groups, and no rebound spike appeared later, so the oil mainly flattened the first surge. Other fats varied: flaxseed oil resembled olive oil, fish oil did little, and lard worked better than coconut oil.

Olive Oil Still Blunted Blood Sugar Spikes in Diabetic Mice

To approximate diabetes, the team repeated the test in two kinds of mice. One group received a chemical that damages insulin-producing cells, leaving insulin levels, in the researchers’ words, “markedly reduced.” The other was a strain that develops diabetes on its own. In both, olive oil first lowered the early blood sugar rise compared with water or oil afterward.

Because the oil worked without an insulin boost, hormones from insulin-producing cells are unlikely to be the main drivers, according to the authors. Slower delivery of glucose from the stomach looks like the real action. Chemically damaged mice only approximate human diabetes.

Backup Hormones and a Nerve Helped Slow Stomach Emptying

Next came the question of which hormones matter. Glucagon, a pancreas hormone better known for raising blood sugar, and GLP-1, a gut hormone, can each slow the stomach. Researchers used mice bred without the gene that makes both (it also makes other related hormones), mice missing only the receptor GLP-1 docks onto, and drugs that block each hormone’s pathway.

Without the gene, olive oil lost its power over blood sugar and the stomach. Mice lacking only the GLP-1 receptor largely kept the benefit, and so did mice with either pathway blocked alone. Blocking both weakened the blood sugar benefit and erased any detectable slowing of the stomach. Together, those results point to a backup system: when one hormone’s route is blocked, the other can carry the signal.

A separate experiment targeted the vagus nerve, a communication line between the gut and brain. Researchers tied off the nerve in some mice and performed a similar operation without tying it in others. Two weeks later, olive oil’s effects were weakened or gone, even though the hormones stayed just as high or climbed higher. The nerve may help translate hormone signals into slower digestion, although the surgery itself slowed the stomach, which muddies the comparison.

Why order mattered remains a guess. When glucose arrives first, its quick absorption may dull how glucagon-producing cells in the pancreas respond to fat, the authors propose, while oil first may switch on fat-sensing pathways before blood sugar climbs. How the gut hormones respond is less clear.

Mouse results cannot show that olive oil before eating helps people with diabetes. The dose was large, and only a glucose solution was tested, not full meals. Still, the experiments make a case for testing meal order in human trials, since slowing the stomach worked even when insulin was scarce.

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Disclaimer: This article summarizes a mouse study and is for informational purposes only. It is not medical advice. Anyone with diabetes or another health condition should talk with a healthcare professional before changing diet or treatment.

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