Prebiotics trump probiotics in the battle for a healthy microbiome

Tempting as it may be to down pills and powders to promote gut health, for most of us, sticking to a balanced diet will work best.

There is a huge array of healthy food to choose from when balancing a diet to promote gut health.

For many people who want to improve their gut health, probiotic supplements are the first things that come to mind. With the simple act of taking a probiotic tablet or some powder, the products promise, you can colonise the bowel with millions of beneficial bacteria that promote a healthy microbiome.

What most people don’t know is that the evidence for the benefits of probiotics for general health is patchy. For some specific conditions, certain targeted probiotic supplements may help but, for most people, taking probiotics is probably a very expensive exercise in futility.

Then there are prebiotics, which many people heard of for the first time in 2022 as prebiotic supplements began trending. Prebiotics are backed by strong evidence of improving the microbiome and delivering a suite of health benefits, but the best way to get them is entirely from the food you eat. So it’s ordinary fruits, vegetables, grains and legumes, not expensive supplements and probably not even kefir or kimchi, that are a sure path to optimum gut health.

The regulation of the bowels is one of the top benefits of prebiotics, and they also have been shown to have beneficial effects on cholesterol and the immune system.

The best way of getting plenty of prebiotics from nutrition is to eat a diet high in fibre, with plenty of fruit and vegetables.

The links between the health of the microbiome and mental health and potentially neurological conditions are not yet proven but they are being researched extensively.

“There’s no good evidence that people should be taking a probiotic unless they have a defined condition for which we know a probiotic might be beneficial,” says Heidi Staudacher, a research fellow and advanced accredited practising dietitian at the Food & Mood Centre at Deakin University. “I would real­ly only advise a probiotic if an individual has a specific condition, such as irritable bowel syndrome, for which there is evidence that probiotics have some efficacy. We would also need to carefully choose the particular strains or combination of strains that have been shown to be effective in that particular health condition.

“Whereas for the average individual a diet that is high in prebiotics and other types of fibres is likely to have benefits for overall health.”

So what are prebiotics? Whereas probiotic supplements contain live bacteria, prebiotics are a subset of dietary fibres that remain undigested by the body, passing through to the large intestine and functioning as a food source for specific gut microorganisms, which then flourish.

The strict scientific definition of prebiotics laid down by the International Association for Probiotics and Prebiotics defines these fibres as “substrates that are selectively used by host microorganisms conferring a health benefit”. Currently, there are only two subsets of dietary fibre recognised by the IAPP as being prebiotics that confer proven health benefits: the non-digestible fibres known as fructo-oligosaccharides and galacto-oligosaccharides. But there are other types of fibres not yet included in the definition that almost certainly also have beneficial prebiotic effects, such as resistant starch and polyphenols.

The best way of getting plenty of prebiotics from nutrition is to eat a diet high in fibre, with plenty of fruit and vegetables, legumes, whole grain breads and cereals and incorporating nuts and seeds.

Legumes, whole grain breads and cereals and incorporating nuts and seeds are great as well.

Vegetables particularly high in prebiotic fibres include Jerusalem artichoke, garlic, onion, leeks and asparagus. Among the grains, rye is particularly beneficial, as well as wheat bran and barley. Legumes should be included in the diet of anyone who wants to optimise their microbiome. The recommended amount of fibre that every individual should consume daily is at least 25g.

And Staudacher says, generally speaking, it is preferable to get your prebiotics from food rather than supplements.

“If someone aims to eat a higher fibre diet, even just through increasing their legume intake for example, they will be increasing their intake of a range fibres, which will then access the large intestine, meaning that a whole host of different organisms are likely going to benefit,” she says.

“So you may see more complex changes in the composition of the microbiome, in comparison to supplementing with a prebiotic or probiotic supplement.”

The upshot of the message from experts on how to have a happy gut? Ditch the pills, avoid fads such as low-fibre keto diets and eat pretty much exactly as the nutritional guidelines advise.