Fibre (or roughage) is a term you may have heard of, but what is it, you may be wondering? Why am I asked to increase, or decrease the amount of fibre I am eating? This is the one area that I give advice about most often.
Fibre is the residue of carbohydrates (starchy foods) that are left in our bowel after we have digested the food that we eat. So it’s waste then? Well not really, it is food for the good bacteria in our bowel and it’s useful for our health to have a good intake of wholegrain starchy foods. Fibre is found in wholegrain and bran based cereals, oats and oat flour, pulses (peas & beans,) lentils, wholemeal, brown & seeded breads, wholemeal pasta, brown rice, nuts, seeds, dried and fresh fruit and vegetables for example.
Two different kinds of fibre are
Soluble fibre – found in oats, golden linseeds, pulses and certain fruit pulps, and vegetables such as Jerusalem artichokes, this fibre is soluble in water. Soluble fibre is food for our gut bacteria and helps lower cholesterol levels.
Insoluble fibre – this is found in wheat bran, rye and other grains and is also the tough outer coatings on fruits, nuts & seeds, this fibre is not soluble in water. Insoluble fibre reduces constipation and promotes gut health.
We are all aware that we need to have at least 5 portions of fruit and vegetables per day, but little is said about wholegrain foods (2-3 servings per day are advised) – to be healthy we should include these in our diet where we can. The UK Committee On the Medical Aspects of food (1999) say that adults should aim for at least 18g up to 24g of fibre per day, this is rather old advice, however we are still as a population not achieving these levels and we have no reason to change this advice. (Levels may be different in other countries and children also have different requirements.)
So, why is this advice so important? Well we all know that those people who have a low intake get constipated, but longer term, low intake of fibre can be more problematic. But rather than focus on negatives, lets discuss the positive aspects. Six good reasons to increase your fibre intake:
1. High fibre foods take longer to leave our stomach, therefore making us feel fuller for longer, good food then, if you are aiming to manage your weight. This idea may be more complex than just adding fibre to processed food or supplements for example; high fibre foods take longer to eat also, which also may have additional effects on satiety.
2. Foods that contain fibre take longer for the available component to pass into our bodies and this can help to achieve a lower blood sugar level after meals, compared with low fibre food, for people who have type 2 diabetes.
3. Some fibre also provides prebiotic action, giving homes and food for the bacteria that live in our large bowel. Helping increases in numbers of ‘friendly bacteria’ is beneficial, these bacteria produce vitamin K and also make short chain fatty acids, which feeds our gut and keeps it healthy. High numbers of good bacteria also reduce the levels of harmful bacteria in our bowel, the ones that result in illness.
4. Having a higher intake of fibre also protects against bowel cancer (which type of fibre is more protective is disputed – Parkin & Boyd 2011.)
5. Fibre also decreases the time it takes for food to pass through our digestive system, reducing constipation (along with a good fluid intake.)
6. Total and ‘bad’ cholesterol levels are reduced with higher fibre diets, by reducing the amount of cholesterol that is reabsorbed into your body, reducing your risk of heart attacks and stroke.
Therefore, as you can see – lots of good reasons to ensure you eat plenty of sources.
All good advice – so why is it I sometimes give advice to reduce the amount of fibre people eat, isn’t this going to be harmful in the future? People who have bowel conditions that may need to reduce fibre intake are often advised to go on a low fibre or low residue diets because fibre stretches the bowel wall, causing bloating and increased pain, also if the bowel is narrowed high fibre residues may cause a blockage. These may be people with crohn’s disease, colitis, cancer, stricturing (narrowing of the bowel) or adhesions from past surgery. Sometimes the type of fibre may be problematic, such as for people with irritable bowel syndrome and advice is provided to eat fibre that does not result in as much bloating, such as following the Low FODMAP diet for example. All these situations need changes to the amount or type of fibre in the diet, but this is usually a short-term measure, and people are advised to increase their fibre intake back to healthy levels post illness or after surgery. They then need to increase the amount slowly initially, starting with fruits without skins or pith & well cooked vegetables, increasing to foods higher in fibre such as wholegrain breads and pulses when tolerated.
So why not try some sources of fibre if you don’t eat it often? It is always advisable to increase the amount you eat slowly, particularly if you are not used to eating large amounts. Start by including one more portion of fruit (about a handful) or vegetables (2-3 tablespoons or a small salad) per day, till you are eating recommended levels or start with a bowl of wholegrain cereal (30g,) then include wholegrain breads, oats, wholegrain pasta/rice – increase by one item per day and see how tasty it is!
http://summaries.cochrane.org/CD002128/dietary-advice-for-reducing-cardiovascular-risk Free article
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3252068/?tool=pubmed Parkin DM, Boyd, L. (2011) Cancers attributable to dietary factors in the UK in 2010 111 – low consumption of fibre British Journal of Cancer 105 (S27-S30) Free article
N. Babio1,2, R. Balanza1,2, J. Basulto1, M. Bulló1,2 and J. Salas-Salvadó1,2 (2010) Dietary fibre: influence on body weight, glycemic control and plasma cholesterol profile Nutr Hosp. 2010;25(3):327-340 Free article
http://www.diabetes.org.uk/Documents/Reports/Nutritional_guidelines200911.pdf Evidence-based nutrition guidelines for the prevention and management of diabetes
May 2011 diabetes UK Free article
- Probiotics – what are they and can they help my gut? (clinicalalimentary.wordpress.com)