Study May Explain Why People With IBD React to Foods They Once Tolerated

For people living with an inflammatory bowel disease (IBD), foods made with wheat and dairy can bring on uncomfortable symptoms like bloating and gas, even when the disease is in remission. Experts aren’t sure why foods that were once tolerated can suddenly become troublesome like this. But now new research is offering a possible explanation.

The researchers behind the study suggest this may explain why people with IBD, which includes Crohn’s disease and ulcerative colitis (UC), can experience new gastrointestinal (GI) symptoms after eating foods with dairy or gluten. The findings could eventually lead to better ways to diagnose food intolerances and manage food-related reactions in people with IBD by restoring key gut bacteria.

Researchers First Looked to Animal Models for Clues

Your gut is home to a community of microbes called the microbiome, and these helpful germs play an important role in digestion. Researchers wanted to understand whether inflammation in people with IBD could interfere with that work — and make certain foods more likely to cause problems.

The study began in mice, says the study’s senior author, Alberto Caminero Fernandez, PhD, a microbiologist and an associate professor of medicine at McMaster University in Hamilton, Ontario.

Dr. Caminero says the study found that mice with colitis (intestinal inflammation) had reduced levels of certain bacteria required to break down gluten and milk proteins. When gut microbes from inflamed mice were transferred into mice raised without microbes, the recipient mice also became more susceptible to food reactions.

“When the mice consumed the triggering foods, they developed pain, immune activation, and worsening colitis. Importantly, restoring the bacteria that had been lost and that are capable of breaking down these food triggers reversed the food-specific immune reactions in preclinical models,” Caminero says. “We found similar alterations in the microbiota of people with IBD who reported adverse reactions to certain foods, suggesting that a similar process may occur in patients.”

Humans With IBD Had Similar Gut Changes

To test the theory, researchers recruited 104 people with IBD in remission (58 with Crohn’s and 46 with UC) alongside 44 people without IBD. Participants provided stool samples and answered questions about their diet, self-reported food intolerances, and food-related GI symptoms.

Caminero says that self-reported food intolerances were more common in participants with IBD, to the tune of about 85 percent compared with 33 percent in healthy controls. People with IBD reported an average of three food triggers, and dairy, wheat, peanuts, tree nuts, caffeine, and fiber were the most commonly reported.

Stool samples suggested a “consistent” pattern with mouse models, Caminero says. “We found that people with IBD had a distinct gut microbiota compared with healthy controls, characterized by lower microbial diversity and the depletion of specific groups of bacteria,” he says.

In lab testing, stool samples from participants with IBD were less effective at breaking down milk proteins, especially in the group who reported food intolerances.

David Dulaney, MD, a San Antonio–based gastroenterologist and a spokesperson for the American Gastroenterological Association, sees this problem in his own practice.

“We have so many patients who are on treatment and have normal colonoscopies, but they still have symptoms from foods,” he says. “The data presented in this study might give us clues as to why they have such bad reactions to certain foods.”

Can Altering the Gut Microbiome Relieve Symptoms?

Dr. Dulaney, who was not involved with the new study, describes it as a “proof of concept,” with further research needed to determine how the findings in mice apply to people with IBD. “The current therapeutics for altering the gut microbiome in IBD are sparse,” he says.

Caminero’s team is exploring whether restoring bacteria that break down specific food triggers could help people with IBD manage these reactions. He says they’re considering potential probiotic approaches.

“Our research offers a potential path toward identifying and, eventually, treating people with IBD who experience food-related immune reactions. But this work is still at an early stage, and no clinical recommendations should be made based on these findings at this time,” he says.

What to Do if You’re Having Trouble Tolerating Dairy or Gluten

Food-related symptoms deserve attention, but this study isn’t a reason to automatically stop eating dairy or wheat. Accurately identifying food intolerances is an important first step, and restricting food groups can increase the risk of nutritional deficiencies, Caminero says.

Here’s what to do instead.

• Track your symptoms. Keep a food and symptom journal and pay attention to potential triggers, says Danielle Gaffen, RDN, a San Diego–based registered dietitian nutritionist and the founder of Eat Well Crohn’s Colitis, which provides personalized nutrition counseling for people living with IBD.
• Talk with your doctor or an IBD-focused dietitian. Your IBD team needs to clarify if your symptoms reflect active inflammation or another condition, such as celiac disease or food allergies, Gaffen says. She recommends asking about celiac testing before removing gluten from your diet. “A dietitian with experience in IBD can help you pinpoint which foods are truly a problem, because 'dairy' isn't one diagnosis. Lactose, milk protein, fat, and portion size can all play a role,” she says.
• Avoid unnecessary restrictions. Work with your doctor or RD instead of eliminating whole food groups. And don’t reintroduce troublesome foods on your own. “If you suspect a food is a trigger, I’d encourage you not to cut it out on your own,” Gaffen says. Your IBD team can help you build a broad, nutritionally complete diet that accounts for your food intolerances.