Be kind to your intestinal flora and it will be kind to you in return. We are talking about the microbiome, the trillions of bugs in your large intestine living in symbiosis with you.
We have written about the microbiome before. All the good deeds the bugs can do if you just feed them the right raw material. And dietary fibre is the ideal food source to support the needs of the beneficial bugs.
The fibre gap
Insufficient nutrients for our gut bacteria have been linked to a loss of certain beneficial bacterial species in western societies and are likely impacting our immunological and metabolic health. Most westerners consume only half of the amount of dietary fibre recommended by dietary guidelines. Nutritionists refer to this as the “fibre gap,” and it is a problem because dietary fibre is the primary source of nutrition accessible to gut bacteria in humans.
Scientists have long promoted the importance of strategically increasing dietary fibre intake as one path forward in regaining gut microbial biodiversity. Although this advice is far from new, the now proven depletion of the microbiome with a fibre deficient diet adds a new perspective to the western diet that we are currently eating.
Comparative studies between rural communities from Africa and South America and industrialised western communities from Europe and North America have revealed specific adaptations of their microbiomes to their respective lifestyles. These adaptations include higher biodiversity and enrichment of Bacteroidetes and Actinobacteria in rural communities, and an overall reduction in microbial diversity and stability in western populations.
Restoring fibre intake can have immediate effects
Some scientists are concerned that a dramatic shift away from a diet similar to the one under which the human-microbiome symbiosis evolved is a key factor in the rise of non-communicable disorders like obesity. There is also a lot of epidemiological evidence that food products containing dietary fibre can help prevent the development of colon cancer and reduce the incidence of coronary heart disease.
It is clear that people living in non-industrialised societies have an average intake of fibre that is much higher than the low norms of western societies. In an experiment scientists compared the effects of a traditional South-African and a modern American diet. Twenty South Africans gave up their corn porridge and vegetable stews for burgers and fries. And 20 Pittsburghians sacrificed fast food staples for the low-fat, high-fiber fare that South Africans traditionally eat that contained 55 grams of daily dietary fibre. Surprisingly, the Americans had improved markers for colon cancer already within two weeks, while the South Africans showed the opposite effects.
The good news is the finding that changes in the microbiome are largely reversible within a single generation if the fibre intake is increased. However, there are also bad news. With several generations on a fibre deficient diet a progressive loss of diversity is seen, which is not recoverable. So your children and children’s children will lack some of the beneficial microbial species, indicating that extinctions can occur in only a few generations.
It is recommended to eat 25-30 grams of dietary fibres a day from a variety of foods rich in both insoluble and soluble fibre.
Foods higher in insoluble fibre include:
- whole grain breads and cereals
- the outer skins of fruit and vegetables
- nuts and seeds
- raw lentil, kidney beans and chickpeas
Foods higher in soluble fibre include:
- fruits and vegetables
- dried beans and lentils
To help meet your daily dietary fibre requirements look at the below table from the Dietitians Association of Australia:
|3/4 cup whole grain breakfast cereal||4.5g|
|2 slices wholemeal bread||4.5g|
|1 apple (with skin) and 1 orange||5.5g|
|2 cups mixed raw vegetables||10g|
|1/4 cup legumes eg. baked beans||3g|