From the Guidelines
Consuming a mix of soluble and insoluble fiber simultaneously is not recommended as it may exacerbate symptoms in individuals with irritable bowel syndrome (IBS), according to the most recent and highest quality study 1. Instead, soluble fiber, found in foods like oats, beans, apples, and citrus fruits, is efficacious in treating global symptoms of IBS, as stated in the 2022 aga clinical practice update on the role of diet in irritable bowel syndrome: expert review 1. The American College of Gastroenterology Guidelines on the management of IBS also made a strong recommendation for the use of soluble (but not insoluble) fiber for the treatment and improvement of global IBS symptoms 1. Some key points to consider:
- Soluble fiber dissolves in water to form a gel-like substance that slows digestion and helps regulate blood sugar and cholesterol levels.
- Insoluble fiber, found in whole grains, nuts, seeds, and vegetable skins, may exacerbate abdominal pain and bloating in individuals with IBS.
- The recommended daily intake of fiber is 25-30 grams, with a focus on soluble fiber for individuals with IBS.
- It is essential to increase fiber intake gradually and drink plenty of water (at least 8 glasses daily) to help the fiber work effectively and prevent digestive discomfort.
- A low FODMAP diet may be recommended as a second-line dietary therapy for IBS, but its implementation should be supervised by a trained dietitian 1.
From the Research
Digestion Levels and Fiber Consumption
Consuming a mix of soluble and insoluble fiber simultaneously may have varying effects on digestion levels. The key to understanding these effects lies in the different ways these types of fiber interact with the gut microbiota and the digestive system as a whole.
Effects of Soluble and Insoluble Fiber
- Soluble fiber can be easily accessed and metabolized by fiber-degrading microorganisms in the intestine, producing beneficial metabolites 2.
- Insoluble fiber, on the other hand, is less easily broken down and can help with the movement of food through the digestive system, promoting regular bowel movements 3.
- A study comparing the effects of soluble guar fiber and insoluble cereal fiber on high-fat diet-induced obesity in mice found that soluble fiber intake led to increased body weight and markers of insulin resistance, possibly due to increased energy loss via the feces and colonic fermentation 4.
Combining Soluble and Insoluble Fiber
- There is evidence to suggest that the combination of soluble and insoluble fiber can have synergistic effects on the gut microbiota, potentially leading to a more stable digestion level 5.
- However, the optimal ratio of soluble to insoluble fiber for achieving stable digestion levels is not well established and may depend on individual factors, such as the starting composition of the gut microbiota 5, 2.
- A study on the determination of total, soluble, and insoluble dietary fiber in foods found that different types of food have varying contents of these fibers, which could inform dietary choices 6.
Conclusion on Digestion Stability
The current evidence suggests that consuming a mix of soluble and insoluble fiber can have varying effects on digestion levels, depending on the type and amount of fiber consumed, as well as individual factors such as the composition of the gut microbiota 5, 2, 4, 6, 3.