We are increasingly bombarded with marketing buzz words like 'prebiotic food' these days. While prebiotic foods promote good bacteria within the gastrointestinal tract, we don't completely understand their role within the digestive system. However, we know from the research that high-fibre diets exhibit significant health benefits, such as reducing cancer risk and assisting with bodyweight management.
Dietary fibre was first acknowledged in the early 1950s and is defined as a class of carbohydrates called polysaccharides originating from plants. Fibre cannot be broken down and absorbed within the digestive tract, however it feeds the billions of bacteria that live inside us which outnumber our cells by 10 to 1.
Over recent years, inulin, fructooligosaccharides, and other oligosaccharides have been distinguished as a class of dietary fibre. Dietary fibre is either soluble, insoluble, resistant starch or prebiotic, with each playing a different role within the body. Many foods contain the most abundant types - soluble and insoluble - in varying proportions.
Soluble and insoluble fibre are great for the gut and regular bowel motions, while prebiotic fibre stimulates the growth of good bacteria. Dietary fibre moves into the large intestine undigested and undergoes complete or partial fermentation by the good bacteria.
Soluble fibre dissolves in water, forming a gel-like substance within the stomach, slowing the movement of food. This moves into the large intestine where the process of fermentation occurs.
Research has concluded that soluble fibre reduces cholesterol levels and slows the food absorption rate; and it also regulates blood glucose levels, thus reducing the risk of developing diabetes. Insoluble fibre absorbs water from consumed food, which helps soften the contents of the bowel and improving bowel motions, helping to prevent constipation and decrease the risk of intestinal blockage.
A prebiotic is a type of fibre (which includes fructans and galacto-oligosaccharides) that are not digested but pass through the gastrointestinal tract to help stimulate the growth of good bacteria within the large intestine.
Notably, not all fibre is prebiotic. However, many foods containing prebiotics are also excellent sources of soluble and insoluble fibre. The richest sources of prebiotic foods include vegetables (garlic, onion, leeks), legumes (chickpeas, red kidney beans), and fruit including dried fruit.
Clinical data indicates that diets low in fibre play a role in numerous health issues, such as constipation, obesity, colon cancer and cardiovascular disease. Recent findings also suggest a large proportion of Australian adults do not eat the recommended 25-30 grams of fibre a day.
To avoid the above-mentioned health issues, it is important to consume a wide variety of fibre-rich foods, such as nuts, seeds, whole grains, legumes, and fruit and vegetables to reap the health benefits!