Teeming with life, your digestive system is home to trillions of bacteria and other microorganisms. Known as the gut microbiome, this collection of 'small wonders' is driving a rapidly expanding body of research.
Linked to many areas of human health – from obesity and immunity, to inflammation, allergies, mental health and metabolism – research in the past decade has revealed the gut microbiome's crucial role in our overall health and happiness.
With so much still to be explored, now's the time to learn how to take care of your gut's greatest allies.
Science tells us that fibre is your gut's best friend. But when it comes to nourishing your gut bacteria, not all fibre is created equal.
The CSIRO says that Australians generally do a good job of eating enough insoluble fibre (also known as roughage). This type of fibre – found in wheat bran, high-fibre cereals, brown rice, wholemeal products and fruit and vegies – helps to keep your bowels regular. "This is great news," says Jean Hailes naturopath Sandra Villella, "but what we need more of are fermentable fibres such as resistant starch."
Resistant starch is what's known as a prebiotic – a type of carbohydrate that can't be digested by your own body, but is food for your gut's 'good' bacteria.
"Having a healthy balance of gut bacteria is all about being a good host; keep the 'good guys' happy by feeding them the food that they love," says Ms Villella.
Foods rich in resistant starch include lentils, peas, beans, firm bananas, some wholegrain foods, cooked and cooled potato and rice, and cold pasta salad.
When potato, rice or pasta are cooked, then cooled and eaten, resistant starch is created, explains accredited practising dietitian Kim Menzies.
"As it avoids digestion, it makes its way to the large intestine where it can be fermented [or eaten up] by the good gut bacteria," says Ms Menzies.
The end products of fermentation, short chain fatty acids, are "excellent for the health of your intestinal cells", fuelling the 'good' gut bacteria and helping to reduce gut inflammation.
The key to a healthy microbiome may not only be what you put on your plate, but what you leave off it.
Researchers are finding that certain food additives, common in packaged and processed foods, may harm gut bacteria and, in turn, your overall health.
Two common emulsifiers (chemical agents used to give processed foods a smooth texture or extend their shelf life) were tested on mice and found to not only reduce levels of healthy gut bacteria and increase levels of inflammatory gut microbes, but also put them at increased risk of chronic disease.
Artificial sweeteners may also be a cause for concern. Often used in 'diet' or 'sugarfree' products, animal studies have shown that these additives disrupt the balance and diversity of gut bacteria.
However, as Ms Villella explains, the key to knowing what's in your food is to use less packaged foods and build your diet around natural whole foods.
"Keep 'sometimes' foods to sometimes only, check food labels for numbers and additives, and where possible, use simple natural ingredients and make your meals from scratch," she says.
Fermented foods, such as sauerkraut, kimchi, kefir and yoghurt contain good bacteria as an ingredient. Plus, if you learn how to ferment these foods at home, there's the bonus of one less food label to read.
"We cannot always be sure just how many good bacteria are present in home-fermented foods, but provided you prepare them safely and follow instructions, it certainly does no harm," says Ms Villella.
So eating these foods regularly may help to bring the right types of bacteria to your gut, and, most importantly, including a wide variety of resistant starches and fibres in your diet will keep the populations happy.
It's an exciting time in the world of gut microbiome exploration, so watch this space for more developments. In the meantime, give your gut a head-start with our easy Sauerkraut recipe.