It's actually very hard to keep track of fibre consumption because the definitions of what is fibre on a label or in tables was different between the UK and the US .It has changed but a lot of fresh produce in lists and labels in the UK still has fibre according to the older definition.
The 18g figure hasn't been changed but is outdated..
It's hard to explain so I'll just quote
Since the early eighties, the Englyst method for determining the amount of fibre in a food has been used by the food industry in the UK. This method measures plant cell wall components of dietary fibre, referred to as non-starch polysaccharides (NSP). There is inconsistency among EC Member States and the UK’s other trading partners in their methods of analysis. Other EC countries and the USA use the American Association of Analytical Chemists (AOAC) method. This method includes lignin and resistant starches which are not part of the NSP fraction. In December 2000, the Food Standards Agency issued a notice to inform the food industry that the AOAC method would now be used in order to harmonise free trade. However there are issues associated with this change:
- For many foods, using the AOAC method will give higher values for fibre compared to the Englyst method.
- The Dietary Reference Value of 18g as mentioned above is based on the Englyst method. This figure is used by health professionals. Using the AOAC method, the proposed benchmark is 24g. However it is essential that the two figures are not compared directly against each other.
- UK food tables currently give the value for fibre using the Englyst method, yet some foods will have been analysed using the AOAC method. Clearly robust, critically evaluated data is required for all foods using a method that is consistent with the new definition
. However even 24g calculated by the current method is lower than the recent US recommendations for most people.
This video explains why it is considered to be important.
Katie Ferraro'Dietary Fiber: the most important nutrient ?
http://uctv.tv/shows/Dietary-Fiber-The-Most-Important-Nutrient-25638
It is long and really only the first 20-25 minutes is relevant,after that it is based upon a US scenario with US labels and products being discussed.
Waning Ms Ferraro isn't very keen on a low carb diet but she does briefly describe some of the evidence for fibre's importance for heart health, gut health, diabetes, cancer and weight. She doesn't go at all into the gut biome and the food you feed it (ie the fibre) which may be very important
(the coursera course she mentions at the beginning is scheduled to start again at the end of February. I found the course varied, ,sometimes a bit simplistic and a bit too US oriented . Some people would be interested to see the module where Dr Lustig is a guest lecturer. The forums on the course are a real eye opener to the varied views about nutrition )