The Mechanism by Which 'Chewing Solid Food Well' Instantly Boosts the Secretion of the Gastrointestinal Hormone GLP-1 and Optimizes Initial Insulin Secretion and Blood Sugar Control

Physiological experiments using mice have demonstrated that the autocrine amount of “GLP-1 (incretin),” a type of gastrointestinal hormone that is attracting attention in diabetes medications and diet outpatient clinics, fluctuates significantly depending on the “presence or absence of chewing behavior” during a meal. It has been shown that only when solid food is intentionally chewed, rather than simply swallowing a liquified meal, hormone release from the intestines via the vagus nerve is dramatically promoted, directly leading to the stabilization of postprandial blood sugar levels.

This content has been reported with detailed data through basic research at the Health Sciences University of Hokkaido.

The Effect of Differences in Masticatory Dynamics and Chewing Habits in Mice on GLP-1 Secretion | Health Sciences University of Hokkaido Academic Repository (*Findings based on papers included in the academic institution repository)

The Decisive Difference in “GLP-1 Secretion Amount” Between Liquid Food and Solid Food

Glucagon-like peptide-1 (GLP-1) is a hormone secreted from “L cells” present from the lower small intestine to the large intestine. GLP-1 rides the bloodstream to reach the β cells of the pancreas, and in addition to promoting insulin secretion dependent on blood sugar levels, it plays an extremely important role in the body’s entire energy metabolism, such as delaying gastric emptying (the speed at which contents are sent to the intestines) and acting on the central nervous system of the brain to strongly suppress appetite.

In experiments using healthy mice, a comparative evaluation was conducted between “solid feed (conditions where chewing is forced)” and “liquid feed (conditions where chewing can be avoided),” adjusted so that the calories and nutrients ingested are exactly identical. As a result, the following decisive differences were observed.

• Increase in Secretion of Active GLP-1: The group that ingested solid feed while chewing trended significantly higher in postprandial blood active GLP-1 levels compared to the group that swallowed liquid feed.
• Promotion of Initial Insulin Secretion (First-Phase Secretion): Due to the increase in GLP-1 through chewing, the quick release of insulin (initial secretion) from the pancreas was induced without delay, and as a result, postprandial hyperglycemia (blood sugar spikes) was suppressed.

These results mean that at a stage “before” food physically reaches the stomach and intestines and its nutritional components are detected, the movement (chewing) in the oral cavity has already triggered the release of GLP-1.

Direct “Brain-Gut” Communication via Efferent Activity of the Vagus Nerve

Behind the activation of cells in the intestines (L cells) before food reaches the digestive tract is the existence of a complex neural command system called the “Gut-Brain Axis.”

When chewing behavior occurs, mechanical stimulation and taste input in the mouth are instantly transmitted to the brainstem through the trigeminal nerve and others. Then, the efferent activity of the “vagus nerve,” the main trunk of the parasympathetic nervous system, is enhanced, and electrical signals race all the way down to the lower digestive tract. It is suggested that there is a loop where this nerve stimulation directly activates L cells—which undigested food has not even reached yet—from the outside (setting them in a pre-standby state), triggering the early release of GLP-1.

In other words, chewing well can be said to function as an extremely advanced neural input interface to “turn on” the switch of the body’s entire metabolic factory at the first stage of a meal, rather than simply the “physical crushing of food.”

The Possibility of a “Pancreatic β-Cell Protection and Proliferation” Effect due to Chewing Habits

Another important suggestion in the same study is the fact that long-term organic protection and functional enhancement of the endocrine system are brought about in the group with the “habit of regularly chewing solid food.”

When data from long-term breeding experiments were histologically evaluated, it was confirmed that in the group that routinely chewed solid feed, not only was the baseline itself of active GLP-1 elevated during fasting, but the “differentiation and proliferation” of pancreatic β cells that secrete insulin were promoted, and a significant expansion of the β cell area (physical functional enhancement) was confirmed.

This indicates that the behavior of “chewing firmly at every meal” is not merely a transient control of blood sugar levels, but a safe approach that reduces the load on endocrine organs (the pancreas) over time and prevents the fundamental progression of impaired glucose tolerance and type 2 diabetes. Daily chewing is thought to function as a fundamental and non-invasive self-intervention program to naturally increase blood concentrations of GLP-1 without relying on drug administration.