A colourful array of  beans, lentils and split peas, arranged in a wave pattern.

What is fibre?

"Fibre" refers to a family of compounds found in all plants, including fruits, vegetables, legumes, and grains. The fibre family includes cellulose, pectin, gums, psyllium, inulin, fructans, lignins, and resistant starches. These compounds cannot be digested or absorbed by your body. Fibre is not found naturally in foods made from animal sources, such as meat, fish, poultry, or dairy products.

Eating more fibre offers many health benefits, including regularity, lower risk of heart disease and colorectal cancer, and weight management. Maintaining a healthy body weight may reduce breast cancer risk. High-fibre foods are generally lower in fat and rich in vitamins, antioxidants and phytochemicals (beneficial compounds found in plant foods) that may be linked to cancer prevention. Eating more plant foods (fruits, vegetables, legumes, grains, nuts and seeds) will increase your fibre intake and lower your overall cancer risk.

To learn more about fibre, please visit Clinical Nutrition's healthy eating resources.

Fibre intake and breast cancer risk

In 2007, experts at the World Cancer Research Fund and American Institute for Cancer Research reviewed the research on food, nutrition, physical activity, and cancer risk. They concluded that there is limited evidence linking food and nutrition to breast cancer risk. This review included studies that looked for a link between fibre and breast cancer risk. Until more research is done, we cannot say for sure whether or not there is a link between fibre and breast cancer risk. However, the experts found strong evidence that a plant-based diet-high in vegetables, fruits, grains, legumes, nuts and seeds-is linked with lower risk of cancer. This diet would be naturally high in fibre.

The possible link between high fibre intake and breast cancer risk came from studies reporting that breast cancer rates were lower among vegetarians than non-vegetarians. Since fibre comes from plant foods and most fats come from animal foods, vegetarian diets are usually high in fibre and low in fat. As a result, it is hard for researchers to separate the effects of fibre from the effects of fat on breast cancer risk. Other lifestyle factors (such as higher physical activity levels and lower body weights) may also play a role in the reduced rate of breast cancer reported among vegetarians.

Before menopause, fibre-rich diets may lower blood estrogen levels in women. Some plant foods contain phytoestrogens (estrogen-like compounds) that may affect estrogen's action inside the body. More research is needed to find out if these effects may lower breast cancer risk.

Fibre intake and overall health

Although fibre passes through your digestive system without being broken down or absorbed, it supports good health in many ways. High fibre intake (from foods) has not been linked to any negative health effects among healthy people. People who have irritable bowel syndrome or other intestinal problems should talk to their doctor before changing their diet.

Bowel health

Eating foods that are high in fibre helps keep your bowels healthy. Eating wheat bran, psyllium, fruits, and vegetables will help address constipation and, if eaten often, these foods will promote regular bowel movements.

Healthy body weights

Eating foods rich in fibre may help people who want to reach or maintain a healthy body weight by making it easier for them to control their food intake. Fibre causes food to stay in your stomach longer and makes you feel full after eating, which can reduce the desire to snack.

Heart health

Soluble fibre, found in higher amounts in oats, wheat, corn, barley, rice, beans, and psyllium, is linked with lower heart disease risk. Eating foods rich in soluble fibre may lower total cholesterol and low-density lipoprotein (LDL) levels in your blood, which in turn, may lower your risk of heart disease.