Rice bran against intestinal rebellion: a compound that inhibits peristalsis

A natural substance from rice husks can soothe an overly active intestine. But this coin has a flip side — for those who suffer from constipation, it can become a problem.

An unexpected property was found in rice husks, which are usually thrown into waste. The substance that is contained there interferes with the mechanism of intestinal contractions — and does it as if it cuts the wires through which the signal goes to the muscles. Moreover, it does not work selectively, but head-on.

A team of researchers from Toho University (Japan), led by Dr. Keisuke Obara, Dr. Kento Yoshioka and Professor Yoshio Tanaka, conducted an experiment on the smooth muscle of the ileum of guinea pigs. First, the muscles were forced to contract using acetylcholine, histamine, serotonin and prostaglandin F2α. Ferulic acid was then added. And the contractions—regardless of which of the mediators triggered them—were noticeably weaker.

This is similar to the situation when, in a room with a dozen different switches, someone turns off the common switch. The lights go out everywhere, although each switch is responsible for its own light bulb.

How it works and why not for everyone

Ferulic acid does not compete with signaling molecules for receptors—it acts differently. Additional experiments on vascular smooth muscle cells showed that acid suppresses the flow of calcium ions into cells through voltage-dependent channels. And calcium is the main trigger for muscle contraction. Without it, the muscle simply cannot contract.

But here lies the catch.

People with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) suffer from two types of motility disorders. In some, peristalsis is excessively active — hence diarrhea and cramps. In others, on the contrary, it is slowed down, and then constipation develops.

Ferulic acid soothes muscles. This means that it helps the first and potentially harms the second.

Imagine a car with two drivers: one presses on the gas, the other presses on the brake. The acid simply shuts down the engine. For those who want to stop, this is salvation. For anyone trying to get going, it’s a disaster.

Researchers explicitly state: drugs or supplements based on this compound should not be prescribed without taking into account the type of disorder. Otherwise, there is a risk of worsening the condition.

From a test tube to a person is a huge distance

The concentrations of ferulic acid that produced the effect in the laboratory were higher than those typically achieved in the blood with a normal diet. However, in the intestine itself, after eating or taking supplements, the level can be significantly higher — the compound comes into direct contact with the wall, rather than passing through a complex absorption pathway.

It's like if you water a plant with a fertilizer solution — the concentration at the roots is always higher than in the bucket from which you water.

But for now this is only a hypothesis. The researchers emphasize that clinical trials on humans are needed. Only they will show whether the mechanism works in a real organism, what dosages are safe and to whom such intervention is really indicated.

Why this is not just another superfood

At this point they usually start writing: “And now you can eat handfuls of rice bran and be cured of all diseases.” No. It is forbidden.

Ferulic acid is a non-active component that accumulates in the body. Its effect is reversible: as soon as the connection is removed, the muscles return to normal activity. That is, the effect lasts only as long as the substance is present in the intestines. This is not a long-acting drug.

In addition, in whole grains and rice bran, ferulic acid coexists with other compounds, including phytic acid, which can interfere with the absorption of minerals. A balanced diet is one thing. But therapeutic use is completely different, it requires precise dosages and control.

Actually, this is why the work of the Japanese group is a foundation, and not a ready-made solution. They showed the mechanism. Now the task is to test it in the clinic.

Prostaglandin F2α, by the way, was among the mediators whose action the acid successfully suppressed. This is not a minor detail: prostaglandins are actively involved in inflammatory processes in the intestines, and if the compound blocks this pathway too, it may have a double effect.

What's next

Clinical trials are expensive and time-consuming. It will take years to confirm safety and effectiveness. But the very fact that a natural compound from food raw materials affects the fundamental mechanisms of motor activity is already attracting the attention of pharmacologists.

Perhaps ferulic acid will become the basis for a new class of drugs — or will remain in the status of an interesting laboratory observation. This happens often in science. But the direction has been chosen correctly.

In the end, if a compound from rice husks, which millions of tons are simply thrown away, can make life easier for patients with diarrheal forms of IBD, it will not be just a discovery. This will be an economically significant story.

Sources:

1. Toho University. «Rice bran compound may help ease irritable bowel symptoms.» ScienceDaily, 30 July 2026. https://www.sciencedaily.com/releases/2026/07/260729010742.htm

Obara K, Yoshioka K, Shimada A, et al. Ferulic acid suppresses guinea pig ileal longitudinal smooth muscle contractions by inhibiting voltage-dependent Ca2+ channels. J Pharmacol Sci. 2025;158(4):289-293. https://doi.org/10.1016/j.jphs.2025.05.012

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