Fiber in Insects and Crustaceans May Aid Weight Loss

In a new mouse study, scientists discovered that chitin — a fiber found in bugs, shrimp, lobsters, and mushrooms — may aid digestion and reduce obesity.

When it comes to dietary fiber, most people think of whole grains, fruits, and vegetables. But crustacean shells, insects, and mushrooms also contain hefty amounts of fiber, despite the ick factor associated with one, possibly two of those foods.

The type of fiber contained in these organisms is called chitin — a polysaccharide derived from modified glucose. It's found in the exoskeletons of bugs, the hard shells of crustaceans like shrimp, and the cell walls of fungi like mushrooms.

Though many people consider mushrooms delicious, eating shrimp shells and insects is probably not on most people's culinary bucket list. And even if they were palatable, most animals, including humans, cannot successfully digest chitin. Those that can have specific bacteria and microorganisms in their digestive tracts that break down chitin's fibrous texture.

However, new mouse research published on September 7 in Science suggests that chitin contained in these organisms may activate the immune system, leading to a reduction in body fat and less weight gain.

In the study, Washington University School of Medicine researchers found that when they gave chitin to germ-free mice fed a high-fat diet, the rodents who couldn't break the fiber down and digest it gained less weight and had lower body fat measurements than mice not given chitin or those that were able to digest the fiber.

Still, even mice that could digest chitin experienced some metabolic benefits.

Moreover, the scientists discovered that chitin, once consumed, distends the stomach, causing activation of a type 2 allergic immune response. This response ramps up the production of specific enzymes called chitinases, which are needed to break down chitin.

The scientists say these activated cells may also produce lipase, which could explain the obesity resistance of mice fed the high-fat diet and chitin.

In mice with gut bacteria, chitin changed the bacterial composition in the lower gastrointestinal tract. The study authors say this shows that gut microbiota also adapts to chitin after it leaves the stomach.

"Obesity is an epidemic," said lead researcher Steven Van Dyken, Ph.D., an assistant professor of pathology & immunology at Washington University School of Medicine.

"What we put into our bodies has a profound effect on our physiology and on how we metabolize food. We're investigating ways to counteract obesity based on what we learn about how the immune system is engaged by diet," Van Dyken adds.

The team plans to research the effects of chitin in humans to determine whether it could help control weight gain and obesity.

"We have several ways to inhibit stomach chitinases," Van Dyken notes. "Pairing those approaches with a chitin-containing food might have a very real metabolic benefit."

Still, consuming insects and crustaceans to obtain chitin can be harmful. For example, some insects harbor dangerous bacteria, viruses, and fungi. Moreover, cases of botulism have been linked to insect consumption. In addition, eating chitin from insects or crustacean shells could cause a reaction similar to a shellfish allergy.

Therefore, because this study used mice and not people, more research is needed to determine whether chitin and the organisms that contain it are safe for human consumption.

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