Inulin, a type of fiber found naturally in foods like bananas, asparagus, and garlic, is often concentrated in dietary supplements for its health benefits. Known to promote gut health and reduce inflammation, inulin has been praised as a key ingredient in high-fiber diets.
However, a recent study by researchers at Weill Cornell Medicine suggests that inulin might also trigger a specific type of immune response that could have mixed effects on health.
The study revealed that inulin can promote type 2 inflammation, a kind of immune response associated with allergies and asthma.
Type 2 inflammation is thought to have evolved in mammals as a defense against parasitic worm infections, but it can also be activated inappropriately, leading to conditions like seasonal allergies and asthma.
Despite this potential downside, type 2 inflammation also plays a role in tissue repair and may not be harmful in healthy individuals.
The researchers investigated how inulin affects the immune system by feeding mice an inulin-rich diet for two weeks. They compared these mice to another group that did not receive inulin.
The mice on the inulin diet showed a significant increase in white blood cells called eosinophils in their gut and lungs. Eosinophils are a hallmark of type 2 inflammation and are typically found in people with allergies or asthma.
Further analysis revealed that the inflammation was triggered by immune cells known as group 2 innate lymphoid cells (ILC2s). These cells were activated by higher levels of bile acids in the blood, which were altered by gut bacteria responding to inulin.
When the researchers removed the bile acid receptor in the mice, the inflammation caused by inulin disappeared, confirming the link between gut bacteria, bile acid metabolism, and type 2 inflammation.
Interestingly, while inulin appeared to worsen allergen-induced airway inflammation in mice, it also enhanced the production of regulatory T (Treg) cells. These immune cells are known for their anti-inflammatory effects and play a crucial role in maintaining immune balance.
This dual action of inulin—promoting both inflammation and anti-inflammatory responses—suggests that its impact on health depends on the context.
For healthy individuals, the type 2 immune response triggered by inulin might not be a problem and could even be beneficial. In the study, the inflammation caused by inulin helped the mice defend against parasitic worm infections.
Additionally, inulin’s ability to boost Treg cells suggests it may still have anti-inflammatory benefits that outweigh its potential to promote type 2 inflammation.
The findings do not imply that inulin is harmful, but they highlight the complexity of how dietary fibers interact with the immune system.
For people with asthma, allergies, or other inflammatory conditions, it might be worth discussing inulin supplements with a healthcare provider to determine whether they are a good fit.
Overall, this study sheds light on how inulin works in the body, balancing its well-known benefits for gut health with its potential to activate certain immune responses.
It’s a reminder that even commonly recommended supplements can have diverse effects, depending on an individual’s health and immune system.
The study, conducted by Dr. David Artis and his team, was published in Nature. It opens the door to more research on how different types of dietary fibers influence health and immune function.
If you care about lung health, please read studies about marijuana’s effects on lung health, and why some non-smokers get lung disease and some heavy smokers do not.
For more information about health, please see recent studies that olive oil may help you live longer, and vitamin D could help lower the risk of autoimmune diseases.
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