Science magazine recently reported that adding small amounts of soil from one terrain such as a wild meadow can ‘inoculate’ barren soil elsewhere. It is of course the uncountable organisms in the healthy soil that achieve this effect – the microscopic bacteria and fungi, nematode worms and other invertebrates. Different communities of these organisms in soil will form relationships with different plants, and so choosing the right soil to draw from will influence which plants grow best in the inoculated soil. This is a dramatic discovery since attempts to restore grasslands, forests and other precious damaged ecosystems are often either unsuccessful or take many years to work.
This is yet another wondrous example of the mirroring of the external environment with our own human internal environment. More and more, it is being understood how the ecology of the human gut – the richest concentration of bacteria found anywhere in the world – influences virtually every aspect of human health.
The best way to maintain a healthy gut bacteria is through diet – making sure we eat sufficient prebiotics and probiotics.
Dietary prebiotics mostly consist of plant fibres – non-digestible carbohydrates of the kind found in vegetables (especially dark green vegetables and vegetable leaves, stems and skins), fruit (especially skin, pith and seeds), cereal brans (in wholegrain cereals), beans, nuts and seeds. Passing undigested through the gastrointestinal tract and fermenting in the large intestine, they encourage the growth of beneficial bacteria, in the same way that adding humus-rich compost to soil supports the microbial environment. Also included in the category of dietary fibre are the hundred kinds of nondigestible oligosaccharides found in human milk.
A typical modern diet contains extremely low quantities of non-digestible carbohydrates. In a study of the microbiota of volunteers from Malawi, Venezuela and the United States, it was observed that the least microbial diversity was found in adult Americans, with other studies showing an enrichment of the microbiota in diets high in whole grain cereals, fruit and nuts and vegetable. As a consequence of the growing understanding of their value, a wide range of prebiotic supplements is now available. It is ironic that an industry which profits from processing the natural fibre out of foods, then profits from selling highly priced ‘functional’ prebiotic products back to consumers to counter the deficiency.
Dietary probiotics are foods which contain beneficial microorganisms that are believed to support the microbiota of the digestive system. All traditional diets contain naturally fermented foods that function as probiotics. These include live yoghurt, kefir (a fermented milk drink), cheeses made from unpasteurised milk, unpasteurised sauerkraut and other brine-fermented vegetables, unpasteurised miso and natto (fermented soybean products), unpasteurised soy sauce (nama shoyu), kombucha (a fermented drink made from tea and drunk in China, Japan, Korea and Russia), kimchi (Korean fermented cabbage) and many more.
As with prebiotics, there is an industry selling probiotic supplements. While dietary probiotics are clearly preferable for a host of reasons, there are situations where manufactured probiotics may be valuable for those suffering from gastrointestinal infections or after taking antibiotics.
Probiotics have been found to be helpful – indeed among the few treatments available – for antibiotic induced diarrhoea (including Clostridium difficile) and viral gastroenteritis. They may also help in cases of ulcerative colitis, infectious diarrhoea, irritable bowel syndrome, atopic dermatitis and bacterial vaginosis, as well as reducing cholesterol, helping lower blood pressure, countering general atopy (a tendency to be hyperallergic), improving immune function and reducing inflammation. Children (three to five years old) given daily probiotics for six months during the winter had fewer days off school and a reduced incidence of fever, runny nose, cough and antibiotic use compared to those given a placebo. When elite male distance runners were given probiotics during the winter, they suffered half the number of days with upper respiratory tract infections compared to those who were given a placebo.
This blog post is taken in part from my recent book Live Well Live long : Teachings from the Chinese Nourishment of Life Tradition