Prebiotics versus probiotics

It is a fair assumption that most people have heard of probiotics. From celebrity-endorsed yoghurts to funky kombucha cans, it can feel like every item on the aisles of food health stores has the label of ‘probiotic’. Someone may not know the intricacies in the science behind how they work, but – thanks to the abundance of adverts for yoghurt drinks showing women carefully caressing their bellies – they can probably deduce probiotics are a benefit to the gut. But what about its similarsounding counterpart, prebiotics?

“I know that people probably know more about probiotics than prebiotics, they’re everywhere, all over the health food stores”, agrees Dr Alexandra Shustina, founder of Whole Gut Health. “People think they understand probiotics better than prebiotics because they’re just more out there. People see that the [concept of a] probiotic is easier to grasp, like, ‘I’m just putting a good bug in there’. Whereas with a prebiotic, you [have] got to know a little more and think, ‘Well, why do I need it?’”

Despite being only a letter different in spelling, prebiotics and probiotics are actually vastly different with distinct functions. While Shustina refers to them as “bugs”, the WHO defines probiotics as live microorganisms that live in the gut.

These can be yeast or ‘good bacteria’ found naturally occurring in fermented foods or taken as supplements. In contrast, prebiotics are not living organisms, but they are nondigestible food ingredients that strategically support the ‘good bacteria’ already in the gut. Dr Mastaneh Sharafi, vice-president of scientific and clinical affairs at Ritual, explains the difference using the analogy, “We like to think of the gut like a garden. Prebiotics are like the elements that help plants grow. In some cases, representing the soil, sun and water [or] like gardeners cutting back the weeds and creating space for new growth. Probiotics are like the plants that grow.”

Prebiotics are a source of food for healthy bacteria and are typically found in complex carbohydrates. These are difficult for the digestive system to process, meaning they arrive largely intact in the colon where they act as nutrients for the beneficial bacteria that reside there.

A gut feeling

While historically prebiotics have been underresearched in comparison with probiotics, this has started to change in recent years with researchers now suggesting prebiotics may be just as important as probiotics in promoting gut health. Dr Megan Rossi, founder of The Gut Health Doctor, outlines the benefits of prebiotics, “There is sound scientific evidence for the benefits, including improving blood-sugar control, helping keep the gut microbiome healthy, appetite regulation, helping calcium absorption, therefore, supporting bone health, and some emerging trials suggesting they can help optimise immunity.”

She continues in greater detail, “The main prebiotics include inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), which are found in over 35,000 plant species.” While prebiotics generally come from plant-based foods, there are some foods that are naturally higher in prebiotics, such as garlic, onions and leeks. However, Rossi advices that rather than fixating on eating specific high-prebiotic plants, “if you eat a diverse range of plant-based foods you’re likely getting sufficient prebiotics”.

While most people can get prebiotics by consuming the recommended daily intake of fibre, Rossi points out that not all fibres are prebiotics and that in order to gain prebiotic status, the food has to demonstrate its health benefits via scientific studies.

Shustina is equally enthusiastic in support of a plant-based diet: “By eating a predominantly plantbased, whole and clean diet, you’re surely going to be getting enough prebiotics for a healthy, balanced person.” She advises anyone looking to increase prebiotics in their diet should start by looking at things that have plant-based fibre and naturally have prebiotics in them.

However, she stresses there is no need to be granular when watching your prebiotics intake, advising, “I think the general recommendations [of fibre is] 25–35g, but I wouldn’t start it that way. I don’t think we need to go to that extreme. I think we can just kind of start like a clean, healthy predominantly, maybe like 75% plant based, 25% animal-based diet.”

One man’s poison is another man’s cure

Shustina emphasises that any lifestyle or diet change, including prebiotics, should be considered as a constantly evolving process of checking in with the body to see how it is reacting. “If someone’s in a good place in their health, for example, they’re not having different bowel issues or anything like that, that’s when you can fine tune-it from there based on your needs. If you notice that you start getting bloated, that’s a big thing. The bloating afterwards, a lot of times occurs when bacteria is fermenting. So, you may want to scale that [intake] down.”

This cautious approach is wise. While the use of prebiotics is not considered dangerous, eating too many could cause discomfort in some people. As bacteria feed on the prebiotics, they ferment and produce gas which can lead to bloating or abdominal discomfort in some people. Shustina jokes, “it depends on the person. There are people who don’t tolerate it as well. There’s no one size fits all, one man’s poison is another man’s cure.”

It is generally advised that those living with IBS may not tolerate prebiotic foods in large quantities. Rossi stresses that, while it’s important to include some prebiotic foods in your diet regularly, more is not always better. She explains that someone’s tolerance can depend on what the type of prebiotic taken, the dose and the duration, specifying, “Bifidobacteria is a beneficial gut bacterium that is typically lower in number in the guts of those living with IBS. Researchers have, therefore, been trying to find out if prebiotics may help symptom management in IBS through their ability to increase Bifidobacteria levels.

“A systematic review and meta-analysis by researchers at King’s College London found that, for those with IBS, specific types of prebiotics (inulin-type fructans including inulin and oligofructose) unfortunately have no effect on abdominal pain or bloating, and may even worsen flatulence. However, they do increase the number of Bifidobacteria, and were better tolerated when doses were less than 6g per day.”

Taking a food-first approach

All three experts agree in encouraging a food-first approach when looking to increase the intake of prebiotics. For the majority of people, taking a prebiotic supplement can be unnecessary. However, if a person is averse to prebiotic-rich food, for example they follow a low FODMAP diet, this is where a supplement can help.

Sharafi advises that someone consults with their healthcare professional to check if prebiotics are compatible with their diet. In fact, she strongly recommends good general awareness before taking any type of supplement, “It’s important to check the dosage and form of the prebiotic on the supplement facts label. The dosage and form should be backed by clinical studies. Prebiotics like inulin, FOS, and GOS usually require doses of over 3g per day in order to be impactful in adults.”

For those suffering with IBS, Shustina recommends looking to probiotics, rather than prebiotics, to help elevate symptoms, “If someone has an inflammatory condition with a dysbiotic pattern – that is when the stools are more loose, for example, like IBS with diarrhoea or ulcerative colitis – then probiotics are more helpful.” She explains that probiotics can ease bowel movements as they help move things along “in a way that is not constipating and actually promotes emptying”. However, that means on the opposite side of the spectrum, for those who suffer with constipation as a symptom of inflammation, probiotics can make those symptoms worse.

While it may take some trial and error to find the appropriate levels that works for each individual, this demonstrates the importance of having a diverse diet to ensure you have plenty of prebiotics and probiotics to promote healthy digestion. This sentiment is echoed by Rossi, “The two should be considered together as part of a comprehensive approach to gut health and as such we are seeing an increase in research on prebiotics and their potential health benefits.”