IBS may be helped by products which provide a protective coating or to absorb irritants in the intestine.

Compounds which can contribute to a protective layer in the intestine include xyloglucan, pea protein, derived from garden peas (Pisum sativum), and tannins extracted from grape seed.^9,25,27,28

Xyloglucan is a hemicellulose polysaccharide extracted from plant cell walls. It comprises a cellulose-like backbone with sidechains of xylose and galactosyl-xylose substituents. This gives it a mucin-like structure similar to epithelial cell secretions. Xyloglucan can stick to the intestinal wall as a physical barrier protecting against damaging agents including microbes, allergens and other pro-inflammatory compounds.²⁶

Animal studies have shown a combination of xyloglucan and pea protein can reduce gut contractions and visceral sensitivity, while reducing gut permeability, improving intestinal functioning. The addition of tannins to the combination has been shown to control diarrhoea and alleviate clinical symptoms including bloating and abdominal pain in IBS-D.^9,28,30

Colloidal silicic acid (molecules comprising silica, oxide and hydroxyl groups such as Si(OH)₄ or SiO₃(OH)₂) activity in IBS may derive from its high adsorption capacity for irritant substances found in the gut (such as reactive enterotoxins, pathogens, and bile acids) and a potential muco-protective effect.³¹

As the activity of products containing these protective barriers compounds is due to a physical effect, rather than pharmacological, these products are classified as medical devices.