Inulin is a natural type of fiber found in foods such as bananas, garlic, onions, asparagus, and chicory root. It is also a common ingredient in fiber supplements and many processed foods.
Because it feeds healthy gut bacteria, inulin has long been praised for improving digestion, supporting gut health, and helping reduce inflammation.
Scientists are continuing to discover that the relationship between food and health is more complex than it first appears.
A new study from researchers at Weill Cornell Medicine suggests that although inulin has many health benefits, it can also affect the immune system in ways that may not be helpful for everyone.
The research, led by Dr. David Artis and published in the journal Nature, focused on a type of immune response known as type 2 inflammation.
This response originally evolved to protect the body from parasitic worms. Today, however, it is also linked to conditions such as asthma, hay fever, and other allergies.
Type 2 inflammation is not always harmful. It also helps repair damaged tissues and supports normal healing. The researchers wanted to find out whether inulin could influence this part of the immune system and, if so, how it happened.
To investigate, the team fed one group of mice a diet rich in inulin for two weeks while another group received a normal diet. The mice that ate more inulin developed higher numbers of eosinophils, a type of white blood cell often found in people with allergies and asthma. These changes appeared in both the lungs and the digestive tract.
The scientists then looked more closely at what was happening inside the body. They found that special immune cells called group 2 innate lymphoid cells, or ILC2s, had become more active. These cells appeared to respond to changes in bile acids, chemicals made by the liver that help digest fats.
The study showed that inulin changed the balance of bacteria living in the gut. Those changes altered the types of bile acids produced, which then activated the immune cells. When the researchers blocked the receptor that detects bile acids, the extra inflammation disappeared, confirming that this pathway was responsible.
The findings were not entirely negative. The researchers also discovered that inulin increased the number of regulatory T cells, often called Tregs. These cells help keep the immune system under control and prevent excessive inflammation, creating a balance between activating and calming immune responses.
For most healthy people, these immune changes are unlikely to cause problems and may even provide benefits, such as supporting tissue repair or helping the body defend itself against parasites. However, people who have asthma, allergies, or other immune-related conditions may wish to speak with their healthcare provider before taking large amounts of inulin supplements.
The researchers stress that this study does not mean inulin is harmful. Instead, it shows that natural fibers can have complex effects that depend on a person’s health, gut bacteria, and immune system. Future research may help scientists design diets and treatments that use these effects to improve health while reducing unwanted immune reactions.
If you care about nutrition, please read studies about the best time to take vitamins to prevent heart disease, and vitamin D supplements strongly reduce cancer death.
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