Ever since the 1980s, when The F-Plan Diet exploded on to the scene, weвЂ™ve all known that high fiber foods are good for us and that we should all be trying to eat more of it. Audrey Eyton, author of that hugely popular slimming book, brought fibrous food into our modern-day consciousness by extolling its virtues as an indispensable aid to weight loss. But nearly 2,500 years ago, Hippocrates was the first to recognize the benefits of fibrous food by praising wholemeal bread вЂњfor its salutary effect upon the bowelвЂќ.
So what exactly is fiber and why should we be aiming high with our intakes?
What is fiber?
Fiber is found in plant foods and can be divided into two types. Firstly, there is the type that helps to give structure to leaves and stalks, stems and fruit, which is known as insoluble fiber. It is not possible for our digestive systems to break down this type of fiber very effectively, so much of it passes through our intestines almost intact. While this type of fiber makes its journey through our small intestine and colon, it seems to have lots of benefits, not least helping to bulk out our stools, ease bowel movements and avoid constipation.
Insoluble fiber is what gives wholemeal bread and wholegrain pasta its brown color, but it is also present in lots of colorful fruits and vegetables. For example, it is in the stalks of broccoli, where it helps to give structure, and the white membranes you find in citrus fruit such as oranges and grapefruit.
The second type of fiber is known as soluble fiber and is found in fruits such as apples and pears, vegetables such as peas and lentils and also in nuts and cereals including oats. Soluble fiber is made up of gums, pectins (used to help set jam) and mucilages that swell up when they come into contact with water in your stomach and intestine, turning the soluble fiber into a sticky glue-like substance. When this happens it helps to keep us feeling full as well as having a beneficial effect on cholesterol and blood-sugar levels.
How much fiber do we need?
Different countries have varying guidelines for the total amount of fiber we should be aiming for. In the UK this is 18g a day, in the US they have loftier goals of 25-35g a day. To give this a sense of perspective, it is still not very much compared with regular daily intakes in, for example, rural African countries, where it is possible to get 60g a day of good food grade fiber through eating the local, largely unrefined diet that is full of both types of fiber.
Studies looking at the consequences of different diets have shown that we produce around 100g of stools a day and it takes 83 hours for a meal to complete its journey through our digestive systems.
However, our African counterparts, who eat much higher fiber diets, produce almost five times this and it takes just 34 hours to pass through their digestive systems.
Rather than worrying about the exact amount of fiber we should be eating, the general message is that a lot of us are not hitting the recommended target. Most adults would benefit from eating more fiber, so consider swapping to wholegrain pastas, bread, rice and cereals and tucking into plenty of fruit and vegetables each day.