Nutrition Research > Fibre
DIETARY FIBRE
Quick Facts
Canadians are not getting enough dietary fibre.
The benefits of dietary fibre go beyond regularity and are important for disease risk reduction, good gut health and more.
Foods made with wheat, particularly whole grain or whole wheat, are great choices for increasing dietary fibre consumption.
Subjects Explored
Canadians are missing out on dietary fibre
Canadian adults need between 25-38 g per day of dietary fibre; however, most are not reaching this amount. Dietary fiber has been classified as a nutrient of public health concern by the National Academy of Medicine (formerly the Institute of Medicine) because under-consumption has been linked in scientific literature to adverse health outcomes.
In fact, most Canadians are only reaching about 50 per cent of the recommended amount of fibre intake per day. This can lead to constipation, digestive issues, higher body weight, and even an increased risk of some diseases such as intestinal cancers.
Studies on the fibre intake of Canadian children from 2015 and more recent data on food intake from American children aged 1 to 8 years old suggest that most children are also only reaching about 50 per cent of the recommended amount of dietary fibre intake per day.
Recommendations for dietary fibre intake depend on age, gender, and life stage (such as pregnancy). Skip to the chart here.
What is dietary fibre?
Dietary fibre comes from plant-based foods, and are the parts of the plants that cannot be digested or absorbed by our gut. Dietary fibre is not one specific compound, but a group of compounds that make up the roughage or bulk of a plant. You won’t find dietary fibre in meat or dairy products.
Whole grains such as 100 per cent whole grain whole wheat are a higher source of fibre than other types of wheat flours (such as whole wheat or white enriched flour), but all wheat flours contain fibre.
There are different types of dietary fibre; many people are familiar with the terms ‘soluble’ and ‘insoluble’, but it is equally important to discuss fermentability of fibre when referring to health, especially gut health, and risk of diseases.
What is fermentable dietary fibre?
Because we do not digest or absorb dietary fibres, these compounds make their way to our large intestine mostly intact and it is our gut bacteria, or microbiota, that break down the fibre compounds. This process is called fermentation. Through the fermentation process short-chain fatty acids (SCFA) are produced. The majority of the SCFAs produced are acetate, propionate, and butyrate, each with their own beneficial function. These compounds are either used by our gut bacteria for energy or absorbed the cells of our intestines (enterocytes) to have effects throughout our body.
While all dietary fibre is beneficial, the fibres that are fermented (and therefore produce SCFA) elicit more health benefits as they:
- Reduce our gut’s pH which creates optimal conditions for the growth of good bacteria
- Interact with the barrier of our gut, improving the protection it provides
- Enhance absorption of minerals by our gut
- Provide energy for our gut bacteria and for us
Through fermentation the SCFA compounds signal a full systemic response in our bodies. For example, they can help our bodies feel full to support healthy body weight management in adults and also play a role in the regulation of blood glucose.
Beyond the direct effects SCFAs have on our colon, microbiota, and overall gut environment (listed above), SCFAs also act as messengers that regulate gene expression, stimulate hormone and gut peptide synthesis, and initiate other pathways in peripheral tissues such as increased glucose utilization and reduced cholesterol synthesis. These effects beyond our gut have implications for disease risk reduction and human health.
When consumed in adequate amounts, they can:
- Promote satiety/fullness for longer
- Improves blood cholesterol levels
- Help control blood sugar levels after eating
- Reduce the risk of heart disease
- Keep you regular (laxative and bulking)
- Help maintain a healthy body weight
- Reduce the risk of colorectal cancer
Sources of dietary fibre include:
Whole grains like wheat and oats, fruits, vegetables, legumes, and nuts and seeds
Wheat as a source of dietary fibre
Much of the research related to wheat and our health has to do specifically with the benefits of the dietary fibre that is naturally found in whole grain whole wheat products.
The amount of dietary fibre in wheat ranges from 9-20% of the kernel by weight, and is made up of both insoluble and soluble fibre. The bran contains most of the dietary fibre found in the wheat kernel, however the starchy endosperm also contains some dietary fibre. This means that whole grain and whole wheat flours will have the most fibre content as they contain the entire wheat kernel.
Refined grains can still be a source of fibre. White bread, made with enriched wheat flour has 1 g of fibre per slice while whole grain whole wheat bread has 2 g of fibre per slice – making both a good choice.
Benefits of dietary fibre for human health
Dietary Fibre Supports a Healthy Body Weight
The evidence is overwhelmingly positive that the consumption of dietary fibre, particularly from whole grains, contributes to body weight management in adults.
Whole grains can promote satiety or a feeling of fullness and decrease appetite.
Dietary fibre’s role in managing diabetes
Maintaining a healthy body weight is also beneficial for other diseases such as diabetes.
Research shows that dietary fibre intake is related to a reduced risk of diabetes. This is mainly due to the combined beneficial effects that whole grains and fibre consumption have on enhancing insulin response and reducing blood glucose levels in the blood after a meal.
Read more about Diabetes here or check out the studies below.
Gut health, colon cancer, and irritable bowel syndrome
Healthy beneficial bacteria in our intestine are important for the successful digestion of food and the absorption of nutrients. They are also important due to the role our gut bacteria play in modulating the risk of many diseases.
The majority of the research on grains and wheat, in particular, show beneficial effects from the consumption of these foods on our gut health and gut microbiota. Many of these studies used whole grain breakfast cereals and saw improvements in the number and diversity of beneficial gut bacteria. These results are likely due to the fibre content of these foods.
Learn more about digestion and gut health here, or with the links below.
Observational studies show a link between the consumption of whole grains and fibre and a reduced risk of colorectal cancer.
The combined data from 10 studies found that the consumption of 10 g per day of cereal dietary fibre intake was associated with a 9% decrease in colorectal cancer risk.
The evidence is less conclusive when looking at dietary fibre and irritable bowel syndrome (IBS).
Read the studies:
Impact of dietary fibre on cholesterol and cardiovascular disease
The beneficial effects of dietary fibre consumption on cardiovascular disease (CVD) protection have been well documented in literature. This is mostly due to the role fibre plays in reducing cholesterol absorption which can reduce the progression of plaque build up in blood vessels.
Based on observational data, there appears to be a relationship between high dietary fibre and whole grain intake and a lower risk of cardiovascular disease.
Read more about Wheat and Heart Disease here.
Meeting the need for dietary fibre
Canadian recommendations indicate that the amount of fibre you need depends on your age, whether you are male or female and if you are pregnant or breastfeeding.
Cereal grains, including wheat, are an important source of dietary fibre, contributing to about 50% of the current total dietary fibre intake in Western countries. Vegetables deliver about 30 to 49% of the daily dietary fibre intake, while fruits contributed about 16%.
Studies, like this one, indicate that children and adults who consume grain foods (which includes wheat) have higher intakes of dietary fibre.
Read more about dietary fibre recommendations here:
Product claims and what to look for
In general, Health Canada approves three types of claims that can be made on food packaging.
- Nutrient content claims: describe the amount of a nutrient in a particular food but make NO link or statement about the role of that nutrient to the way our body functions (e.g. “High source of fibre”).When evaluating the fibre content claims on a package, some terms have been defined by Health Canada.
- “Source of fibre” means at least 2 g of fibre per serving
- “High source of fibre” is at least 4 g of fibre per serving
- “Very high source of fibre” means at least 6 g of fibre per serving
- Function claims: describes the specific beneficial effects that the consumption of a food or its nutrients has on normal functions of the body. (e.g. “Consuming 7 grams of fibre from coarse wheat bran promotes regularity”).
- Disease risk reduction claims: a statement on packaging that links a food or part of a food to reducing the risk of developing a diet-related disease (e.g. “A healthy diet rich in a variety of vegetables and fruit may help reduce the risk of some types of cancer”).
- Therapeutic claims: claims about the treatment or mitigation of a disease or health-related condition, or about restoring, correcting or modifying body functions (e.g. “Oat fibre helps lower cholesterol”).
Health claims for wheat-based foods
Sometimes the science moves faster than regulation.
Currently, no disease risk reduction or therapeutic health claims related specifically to wheat or the fibre it contains have been approved in Canada.
Only three types of fibre have been approved by Health Canada to make cholesterol lowering claims. These are oat products, psyllium fibre, and other fibre complexes.
Proposed health claims regarding the relationship between whole grains and dietary fibre, in general, and cancer and coronary heart disease were submitted to Health Canada for approval, but at this time, no approved health claims exist.
This means that although the literature may indicate otherwise, food products containing wheat (without other ingredients such as other grains) cannot carry disease risk or therapeutic health claims on the packaging, but they still qualify for nutrient content claims and function claims.
You can read more about labelling and health claims here:
