I hear a lot about needing to eat more fibre but am confused about the different types and how much we should be having. On my box of porridge it talks about “soluble” fibre. Is this the same as roughage and will it make me bloated?

Broadly speaking, there are two types of fibre. One gives structure to plants. It is tough and fibrous and is found in the stalks, skins and leaves of vegetables and fruit as well as the outer coating of grain. The other type is best described as being “gum-like” and is found inside fruit and some grain, including porridge oats.

Both types can be chewed, mixed up with hydrochloric acid in your stomach and bombarded by enzymes in your upper intestine and yet still make it into your colon intact. Therein lies their usefulness.

The first type, often called insoluble fibre or “roughage”, moves through your intestines largely unchanged but gives bulk to the contents of your gut. This makes your stools softer and easier to excrete and speeds up the time that the contents take to pass through your intestines, so that potential carcinogens, for instance, have less chance to wreak havoc.

The second type is known as “soluble” fibre. It comes in quite a few forms such as pectin in apples and pears and beta glucan in oats. Soluble fibre tends to help you to feel full after eating by forming a viscous gel that helps to slow down the speed at which food leaves your stomach. This in turn slows the speed at which blood sugar rises after eating, which is especially useful for helping people with diabetes to control sugar levels in their blood. Beta glucan has the added advantage of binding cholesterol, along with potential carcinogens and mutagens, and taking them out of the body in the stools. This means that eating a diet rich in soluble fibre may help to lower cholesterol as well as the risk of cancer.

When it comes to bloating you can feel a bit distended when you increase your intake of fibre-rich foods, partly because

the bacteria in your colon are able to metabolise a small amount of the fibrous compounds that end up there, with gases produced as a result. With time, the gut adapts and gas production and bloating should reduce. Pulses, such as baked beans, are especially gas-producing.

Two particular types of carbohydrate called raffinose and stachylose in pulses are not broken down efficiently by human beings and, once in the colon, are metabolised by bacteria, which release hydrogen, methane and carbon dioxide in the process. It is wise to introduce pulse vegetables gradually to reduce bloating.

Roughage: boost your intake

The aim is to eat about 18g of fibre a day, so the average person in the UK has to increase his or her intake by 6g daily to meet this target.

As a guide, a slice of wholemeal bread has 1.8g of fibre; a 160g bowl of cooked porridge 1.4g; one wholemeal pitta bread 3.9g; a 180g bowl of cooked brown rice 1.4g; a 220g bowl of cooked wholemeal pasta 7.7g; a serving of broccoli 2.3g; a serving of peas 3.6g; one banana 1g; an apple 1.8g and

100g of raspberries 2.5g.

Dr Denis Burkitt, an authority on fibre in the diet, documented in 1972 that a Ugandan villager eating a high-fibre diet produced 470g of stools a day, which took 36 hours to produce after eating. In comparison, a Royal Navy sailor on a low-fibre diet produced just 104g of stools, which took 83 hours to pass.

Many foods rich in fibre are also rich in supernutrients, vitamins and minerals. But phytates, found in bran in oats for example, can inhibit the absorption of iron needed for energy and preventing low moods.

Times recommends

• Jennifer Aniston, time to be a real bitch
• It may be hard to say so, but conversation is back
• News Review interview: Georgina Baillie