The Health Benefits of Fibre

96% of the UK population fails to eat enough fibre and this statistic is consistently high across much of the developed world. The UK recommended daily amount for fibre is 30g yet the average consumption by an adult is only 20g. Fibre is a nutrient with numerous health benefits. Addressing this fibre gap could have a major effect on public health but it will require behaviour change on behalf of consumers and innovation from manufacturers.

What is fibre?

There are 4 main types of fibre, [DN - link to article] all of which have one thing in common: they are not digested in our small intestine and therefore reach our colon, or large intestine, intact, where they can fulfil a number of beneficial roles. Some will be digested by our gut bacteria, and some will pass all the way through us, playing a more mechanical role in supporting digestion.

The UK Scientific Advisory Committee on Nutrition published a comprehensive report on carbohydrates and health, including an in-depth review of the benefits of fibre to health. Here, we’ll review the main findings, including any more recent, relevant research updates.

Evidence suggests that, to obtain the greatest benefits of fibre, it’s necessary to consume the recommended 30g per day from multiple food sources and fibre types, including wholegrains, pulses, nuts, seeds, vegetables and fruits.

Cardiovascular health

•       Dietary fibre is linked to a reduced risk of cardiovascular disease (CVD), coronary events and stroke

•       Insoluble fibre, which is found in wholegrains, pulses, nuts and seeds, and vegetable fibre may help reduce risk of CVD and coronary events. See also this reference

•       Higher consumption of cereal fibre, such as that from wholegrains like oats, wheat, and rye is linked to reduced risk of coronary events

•       Oat bran and beta glucans may help reduce blood pressure

•       Both of these are also linked to reductions in total and LDL-cholesterol and triglycerides (a type of fat found in the blood)

•       Consuming cereals in general as well as specifically higher fibre breakfast cereals and wholegrains is linked to a lower risk of CVD, stroke and hypertension

•       Resistant oligosaccharides, specifically fructo-oligosaccharides and inulin may help reduce LDL-cholesterol but only in very large amounts, inconsistent with current daily diet. However, brands are beginning to use these fibres in food or they can be purchased as supplements so consumption may increase in the future.

Cancer risk reduction

•       Higher consumption of dietary fibre is linked to a reduced risk of colon and rectal cancer

•       Cereal fibre is linked to a reduced risk of colorectal cancer

•       Wholegrain intake is associated with a reduced risk of colon cancer

Type 2 diabetes

•       Higher consumption of dietary fibre (see also here), and specifically cereal fibre is linked to a reduced risk of type 2 diabetes

•       Eating more insoluble and soluble fibre may reduce risk of type 2 diabetes

•       Wholegrains including wholegrain bread and high fibre cereals are associated with a reduced risk of type 2 diabetes

Gut health

•       Dietary fibre overall, particularly wheat and non-wheat cereal fibre and fruit/veg fibre may increase stool weight and reduce intestinal transit time, thereby supporting digestion

•       Fibre from pulses is also linked to increased stool weight

•       Wheat fibre may increase faecal bulk, reduce intestinal transit time and increase bowel frequency

•       Wholegrain rye bread, maize fibre and rice bran may also reduce intestinal transit time and increase faecal weight

•       Cereal fibre may reduce constipation while wheat fibre might reduce intestinal transit time in those with constipation

•       SACN’s meta-analysis showed non-digestible oligosaccharides (particularly fructo-oligosaccharides) and inulin, when supplemented at 10-30g a day, could increase faecal weight

•       They also showed that doses of >10g fructo-oligosaccharides and 2.4-14.4g galacto-oligosaccharides per day could increase faecal Bifidobacterium species. However, it is not clear whether this effect is either beneficial or biologically relevant. Doses are inconsistent with current population dietary intake but could increase as manufacturers use this type of fibre more widely

•       Resistant starch is linked to increased stool weight at doses ranging from 21.5-37g raw resistant starch per day or 17.4-32g per day retrograde resistant starch. Again these doses are higher than current habitual population intake

•       Resistant starch, when digested by our gut bacteria, can produce short chain fatty acids (SCFA), which can potentially benefit gut and immune function). Again, this is at levels higher than current consumption

•       Resistant oligosaccharides (mostly galacto- but also fructo-oligosaccharides), when included in infant formula may change bacterial balance in the stool, SCFA production and stool pH in babies under 3 months of age, but it’s unclear how this might affect their health. Studies reviewed by SACN showed this effect to be demonstrated at a does of 8g galactooligosaccharides (and optionally fructo-oligosaccharides) per litre formula

Weight management

•       While it feels logical to assume high fibre foods will increase feelings of fullness and thereby reduce calorie intake (and consequently weight), it is hard to show this in studies. We therefore need to do more research on how fibre might influence appetite and weight

•       Higher wholegrain vs refined grain consumption is linked with a lower overall calorie intake but in the context of a study aimed reducing fat intake and increasing consumption of fruits and vegetables

•       Increased consumption of dietary fibre has the potential to induce structural, physicochemical and gastrointestinal site-specific benefits that may be relevant for the treatment of obesity and metabolic syndrome but much more research is needed to understand specific recommendations

•       Some specific soluble fibres (e.g. guar gum, beta glucan, alginate, polydextrose and pectin, when administered before or during a meal, may reduce energy intake and play a role in weight management. Glucomannan, when given in 3 doses of 1g each, in the context of a calorie-reduced diet, has an approved health claim in the UK and EU with regard to weight loss

The evidence base in support of fibre and its benefits to health is strong, but more research is definitely required to build knowledge, in particular around the effects of different fibre types on gut health and weight management.