Fiber is what is not digested in plants – substances such as pectin, cellulose, inulin ... These reach the large intestine, where intestinal bacteria try to process them. These bacteria, mostly derived from fiber, produce short-chain fatty acids (SCFA), such as butyrate and propionate, which:
- aid in the regeneration of the intestinal mucosa,
- reduce inflammatory processes,
- regulate digestion, and
- protect against colon cancer.
Studies show: if an adult consumes the recommended 25–30 grams of fiber daily, they reduce the risk of colorectal cancer, type 2 diabetes, and heart disease.
Where does the problem arise in IBD?
People with inflammatory bowel disease often have an imbalance of bacteria in their intestines (called dysbiosis): fewer healthy bacteria, such as Faecalibacterium prausnitzii, and more bacteria that promote inflammation.
When such individuals consume fiber, their bacteria do not ferment it properly, leaving the fiber undigested, irritating the intestinal wall, and triggering an inflammatory response. Fiber from garlic, artichokes, chicory, asparagus, and bananas, in particular, can be threatening when the appropriate microorganisms are insufficient.
A scientific study from Alberta found that as many as 20 to 40% of IBD patients experience worsening symptoms after consuming these types of fiber.
What specifically happens? – Studies on specific fiber types
Recent research has found that a fiber called inulin (found in garlic, onions, chicory, artichokes) triggers long-lasting inflammation. This means that microbes release bile acids that, through proteins (such as IL-33), cause a strong inflammatory response in some patients, manifested by frequent cramps and pains.
Studies on patients have shown that non-fermented fibers can cause inflammation visible on biopsies – in contrast to fermented fibers, which inhibit inflammation.
Are fibers beneficial at all?
Yes! When prebiotic fibers (those that promote the growth of good bacteria) were introduced in clinical trials, patients with ulcerative colitis had lower CRP values (proteins indicating inflammation), less pain, and improved digestion.
Additionally, epidemiological studies with over 50,000 participants have shown that higher fiber intake reduces the risk of developing Crohn's disease and colitis by between 73% and 80%.
What does this lead to?
- 1. Differentiate fibers by type
Soluble fibers, which dissolve in water (e.g., pectin in apples, oatmeal), are suitable and can be digested by many. In contrast, insoluble fibers (like cellulose from whole-grain foods, nuts, seeds) can trigger cramps, bloating, and diarrhea for patients, especially during disease exacerbation. - 2. Listen to your body - and test tolerance
As researchers from Australia have found, introducing stool analysis for microbiome testing can predict whether a particular type of fiber suits you or not. If the test shows a lack of certain bacteria, it is recommended to avoid fibers from garlic, asparagus, artichokes, bananas, and similar items, as these fall into the endangered category. - 3. Use a gradual dietary reintroduction approach
During periods of non-acute disease, fibers can be gradually introduced – ideally 15–25 grams daily, half of which should be soluble (in the form of cooked vegetables, peeled fruit purees, oatmeal). - 4. Plan your diet with a doctor or nutritionist
Conventional treatments remain the foundation – medications and therapies prescribed by a gastroenterologist. Fiber is a supplement that can positively impact your well-being if introduced thoughtfully.
Specific dietary recommendations
Here are some common-sense suggestions:
- Completely safe options: peeled apples, cooked carrots, oatmeal, light integrated pasta (e.g., white wheat).
- Consume with caution: peeled bananas (some types lack bacteria for fermentation), cooked tomatoes, zucchini.
- Avoid: raw whole grains, nuts, seeds, garlic, onions, artichokes, asparagus ... Follow this until stool tests show that these bacteria can be digested.
A Folk Healing Story
Particularly problematic is the Balkan cuisine, where almost all dishes are prepared with olive oil and whole-grain additives, without cooked foods. By eating raw vegetables and nuts, one triggered severe cramps and pains lasting several days. If this happens to you, switch to soups with oats and cooked potatoes, and add fermented cucumbers. After a few weeks, diarrhea will disappear, abdominal pain will cease, and your body will recover.
The Balkan cuisine is strongly discouraged even for those who have occasional intestinal issues.
After indulging in raw foods rich in insoluble fibers, switch as soon as possible to simple cooked, fermented dishes that improve bacterial balance. Such a transition could be called folk microbial therapy.
Science suggests the following recommendations:
- 25–30 grams of fiber daily – a recommendation
- Up to 80% lower likelihood of IBD with high intake of fruit fibers
- 20–40% of people may experience intestinal inflammation when consuming certain fibers (you must determine which)
- 50% of daily fibers should be soluble during remission (partial and apparent improvement of disease symptoms)
- CRP can decrease with prebiotic fibers (CRP stands for C-reactive protein – a protein produced by the liver in response to inflammation)
- Be cautious of worsening symptoms with insoluble fibers, such as whole grains
When planning a menu that includes cooked vegetables, fermented dishes, and soluble fibers while avoiding gluten and excessive whole-grain foods, you are already taking a significant step. Add in vitamin-rich soups, chamomile or lavender for calming effects, and you will soon see results.
Also, keep in mind that fibers are a double-edged sword: they can heal or irritate. The outcome heavily depends on the balance of bacteria in the gut. Therefore:
- Start with soluble fibers (15–25 grams/day, half soluble),
- slowly introduce insoluble fibers,
- monitor symptoms and CRP,
- adjust your diet based on what makes you feel better,
- always consult with a doctor.
With a thoughtful and tailored intake of fibers, they will become part of the solution rather than the problem.
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