Too much soluble fibre?

One of the books we inherited from Rob's dad was Healthy Eating for IBS, by Sophie Braimbridge and Erica Jankovich. One of the authors is a chef and the other is a dietician, so in addition to having some great recipes, there's also some interesting information on IBS.

On p28 there is a section called Too much soluble fibre:

'A high intake of soluble versus insoluble fibre can lead to excess amounts of food residues available for gut fermentation in the colon. Soluble fibre is metabolised by healthy gut bacteria to produce short chain fatty acids (bacteria) and gases. In certain people who harbour excessive amounts of sulphur-producing bacteria, extra gases such as hydrogen sulphide and methanethiol are also produced, which result in bad smelly wind. The short chain fatty acids feed the colonic bacteria, increasing their quantity and fermentation rate and so producing an increase in bowel gases.

It is a common error, when attempting to increase your fibre intake, to be over-enthusiastic and eat too great a quantity of fruit, vegetables, pulses, nuts and seeds, which are the main sources of soluble fibre in our diet. In order to achieve the right balance, aim to maintain but not exceed the recommended five portions of fruit and vegetables per day and ensure that all starch portions in your meals are those which contain insoluble fibre. Do not make the mistake of counting oats as an insoluble fibre when they are actually classified as a soluble fibre.'

From p22
Soluble fibre
Food types which are predominantly high in soluble fibre are:
- fruits
- vegetables
- legumes
- oats
- barley
- seeds

Insoluble fibre
Foods predominantly high in insoluble fibre are:
- roughage foods with skins, husks and peels, eg spelt, buckwheat, millet, chickpeas
- some fruit and vegetables with their skins and pips, eg tomatoes, courgettes, grapes plus potatoes and other root vegetables
- wheat, rye and all other cereals
- nuts and some legumes, eg almonds, chestnuts, coconut, chickpeas
- rice

How much fibre do we need?
'There is no simple answer to this question. Each person's fibre intake needs to be individually assessed and the contribution of the different fibre sources in their diet ascertained. This information then serves as a basis for dietary manipulation. It should be noted that there is a very fine line to be drawn between having the correct amount and overdoing it in terms of fibre intake. Prudent guidelines (that is, the recommended average for the population) suggest a total fibre intake of 20-30g a day of which 6-10.5g needs to be soluble... It is important to remember that although these guidelines of 20-30g per day are prudent, they may not be appropriate for you. Your type of IBS and an assessment of your particular symptoms and present fibre intake will determine the amount of fibre that is right for you.'