High Fibre Diets & Digestion

By Dietitian Juliette Kellow BSc RD

Q: I know I should eat a high-fibre diet if I want to lose weight but it seems to upset my digestive system. What should I do?

A: Including plenty of fibre-rich foods in your diet can benefit your health in many ways, which is why nutrition experts recommend we all eat more, regardless of whether we’re trying to lose weight. Firstly, a good fibre intake keeps the digestive system in good working order and can help prevent or alleviate conditions such as constipation, haemorrhoids (piles) and diverticular disease. Eating plenty of fibre-rich foods may also reduce the risk of developing bowel cancer. And of course, high-fibre foods can help fill you up, which is why they’re such a great choice if you want to lose weight. Furthermore, most foods that are rich in fibre, are also low in fat and good sources of other nutrients. Wholegrain cereals, for example, are packed with iron and B vitamins, many fruit and veg are good sources of vitamin C, and pulses contain protein, iron and calcium.

Some people find that excessive wind, bloating and even constipation can occur if they suddenly start to eat a lot more fibre, so to prevent this it’s important to introduce fibre-rich foods gradually. This gives your body a chance to get used to them and adapt accordingly. Dietary fibre acts a bit like a sponge in the gut and absorbs water to increase the bulk and softness of the stools, helping to ensure they’re eliminated easily from the body. Therefore, as you increase your intake of fibre, it’s also important to increase your fluid intake. If you don’t drink enough, then constipation may result.

Health guidelines recommend adults should have, on average, 18g of dietary fibre a day. WLR’s nutrition summary on the food diary page gives details of fibre intake so it’s easy enough to check whether you’re having enough. Good sources of fibre include wholegrain breakfast cereals and breads, wholewheat pasta, brown rice, jacket potatoes, peas, beans, lentils, fruit, vegetables, nuts and seeds. Ultimately, it’s a good idea to eat a range of different fibre-rich foods rather than always opting for the same few. But when you first start to increase your fibre intake, I suggest you make one change at a time, for example, swapping white bread for wholemeal bread, or cornflakes for branflakes. Once your body has got used to this change, you can introduce another one. Hopefully, this will help to prevent the digestive problems you’ve experienced in the past. If they continue, however, I suggest you see your GP for advice.