Dietary fibre and gut health

Evidence suggests that an adequate intake of dietary fibre may deliver many health benefits.

These include:

• Helping with weight control
• Lowering blood cholesterol
• Decreasing risk of colon cancer
• Decreasing risk of type 2 diabetes and improving control of diabetes
• Helping to prevent and manage constipation, haemorrhoids and diverticulitis

Lowering blood cholesterol

Consuming good amounts of soluble dietary fibre may help with lowering blood cholesterol levels, which may in turn improve blood lipid profiles and lower risk of heart disease.

High blood lipid levels are a risk factor for cardiovascular disease. Soluble dietary fibre can bind bile acids which are secreted into the small intestine to assist with the digestion of fat. Bile is made in the liver and one of its components is cholesterol.

Most bile secreted into the small intestine is reabsorbed back into the blood stream and recycled. Bile that becomes trapped in soluble fibre is not reabsorbed and instead travels to the large intestine where it is excreted in the stool. This means that the cholesterol in the bile is not recycled, and so the liver will need to take more cholesterol from the blood stream to make new bile. This leads to a reduction in blood cholesterol levels, which can lead to an improved blood lipid profile.

Diabetes

Consuming good amounts of soluble dietary fibre may help with blood glucose control. Diets that include high fibre and wholegrain foods might also decrease the risk of developing type 2 diabetes.

Soluble fibre can trap food and its nutrient components, so delaying movement through the gastrointestinal tract. This can slow the absorption of glucose and lead to a slower rise in blood glucose levels after eating. This helps with managing blood glucose levels in those who have diabetes.

Cancer

Evidence suggests that people who eat a diet which is high in dietary fibre have a reduced risk of developing colon cancer.

It may be that dietary fibre binds and removes potential cancer-causing substances from the large bowel, excreting these in the stools. It may also be that when some dietary fibres are fermented in the large intestine producing short-chain fatty acids, that these fatty acids decrease the pH level of the bowel, activating cancer-killing enzymes which may reduce inflammation.

Weight control

Dietary patterns rich in dietary fibre can assist with weight management.

Foods which are high in dietary fibre are usually lower in energy density – so contain less fat and added sugars. This can lead to a lower energy intake which assists with weight loss and weight maintenance. Additionally, dietary fibre attracts and absorbs water in the gastrointestinal tract, which may promote a feeling of satiety or fullness.

Gastrointestinal disorders

Gastrointestinal disorders can include those such as constipation, diverticular disease, and haemorrhoids. A diet which contains healthy amounts of dietary fibre and plenty of fluids will support a healthy bowel. This can assist with preventing several common bowel disorders including constipation, diverticular disease and haemorrhoids.

Dietary fibre attracts and absorbs fluid in the bowel, helping to form large, soft stools which are easier to pass, reducing transit time, and decreasing risk of straining. This supports a healthy bowel wall and regular bowel habits.

Conversely, dry, hard stools can be difficult to pass and lead to straining which can result in haemorrhoids or diverticular disease, where small, pouches or sacs form in the wall of the large intestine. These diverticula (sacs) can become infected, leading to inflammation and abdominal pain.

Dietary fibre assists with GI health

A good intake of dietary fibre, combined with ample fluids can help to ensure a large, soft stool and ease of passage, decreasing the risk of:

• Haemorrhoids
• Compaction of faeces/constipation
• Formation of diverticula
• Colon cancer

Too much dietary fibre

Consuming too much dietary fibre, or increasing intake of dietary fibre too quickly and/or drinking insufficient fluids can increase the risk of the following problems:

• Displacement of other nutritious foods: High fibre foods are bulky and filling. Consuming too much fibre may lead to inadequate intake of other nutrients and/or energy. This might be more relevant for individuals who have a small appetite and are easily ‘filled up’, such as small children and frail, elderly adults.
• Contributing to gastrointestinal discomfort: Such as bloating, gas, constipation or diarrhoea.
• Interference with absorption of minerals and nutrients: Some dietary fibres can bind minerals (such as iron and zinc) as it moves through the digestive tract, and interfere with the absorption of other nutrients. This is generally not a problem if fibre intake is adequate. However, excessive amounts of dietary fibre can cause food to move more quickly through the digestive tract, meaning there is less time for other nutrients to be digested and absorbed.