Dietary fibres

Dietary fibres are a type of carbohydrate found in plant-based food. They are generally not digested by the body but serve an essential function in helping with digestion and overall health. The main classification of fibres is soluble and insoluble, depending on whether or not it dissolves in water. Soluble fibres can help with cholesterol blood sugar levels and hence keep hunger in check, while insoluble fibres promote regular bowel movements and prevent constipation.

Oat bran, barley, nuts, seeds, beans, lentils, and peas are rich in soluble fibre, which can also be found in a psyllium supplement.

Wholewheat flour, wheat bran, brown rice, quinoa, peanuts, almonds, walnuts, pumpkin, chia and sesame seeds, beans and vegetables, such as cauliflower, green beans and potato are good sources of insoluble fibres.

The recommended daily fibre intake is 30g, but the average consumption for adults in the UK is only 18g/day. Increasing fibres in the diet are easy to achieve by:

1. adding extra fruits, seeds and nuts to low-sugar breakfast cereals (oats and whole-grain wheat breakfast cereals are particularly rich in fibre)

2. swapping white bread and pasta for wholemeal

3. adding legumes and pulses to casseroles, curry meals etc

4. increasing intake of resistant starch. Resistant starch is the fibre the gut microbiota uses to produce short-chain fatty acids. SCFAs have many roles; they are a significant energy source for the cells in the large bowel, and one of the SCFAs, butyrate, is known to have anti-cancer properties. They also have a role in immunity, and a lot of research is taking place to elucidate their effect on brain and neurodegenerative diseases like Alzheimer’s disease. Resistant starch is found in bananas, potatoes, grains and pulses.

5. supplementing prebiotics also help in diversifying and helping gut microbiota. For example, onions, garlic, asparagus, artichoke and chicory root are all prebiotic food helping more good gut bacteria to grow.

Many people with IBS have noted that their symptoms can worsen with increased fibre intake. People with IBS where primary symptom is constipation, are likely to benefit from an increased amount of fibres in the diet, albeit gradually. The type of fibre is also critical as several studies have shown that while consuming water-insoluble fibre does not improve IBS symptoms, consuming soluble fibre improves overall IBS symptoms [1]. Fibre supplementation, particularly psyllium, is safe and effective in improving IBS symptoms globally.

[1] Bijkerk CJ, de Wit NJ, Muris JW, Whorwell PJ, Knottnerus JA, Hoes AW. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial. BMJ. 2009;339:b3154. doi: 10.1136/bmj.b3154.