What Are Prebiotics & Should You Be Taking Them?

Have you heard of prebiotics? Are you wondering what prebiotics are and if you should be taking them for IBS?

This post will discuss what prebiotics are, how you can add them to your diet, and what benefits they have in IBS and gut health.

WHAT ARE PREBIOTICS?

Prebiotics are a form of fibre found in some foods, which can help your good gut bacteria to thrive (2). 

Prebiotics help your good gut bacteria by acting as a food source for the bacteria, which then multiply in numbers. This helps to improve your health as gut bacteria plays such a vital role. 

It is important to note that not all fibres are prebiotics (2).

WHY ARE PREBIOTICS BENEFICIAL FOR THE GUT?

The use of prebiotics is suggested to be a good way to improve the levels of good gut bacteria.

This is because a change in normal gut bacteria, typically becoming less diverse, is often seen in digestive health problems such as irritable bowel syndrome and Crohn’s disease (3, 4).  

Therefore, prebiotics help the bacteria in the gut diversify due to it helping good gut bacteria multiple. It can help restore gut bacteria back closer to the ‘normal’, however it must be noted that it may not completely become ‘normal’ again (12). 

HOW CAN I ADD PREBIOTICS TO MY DIET?

You can add prebiotics into your diet in a few ways. The easiest, most practical and affordable way is getting them from food, but you can also take supplements. 

PREBIOTICS IN FOOD

Prebiotics are mainly fructans, inulin or galactooligosaccharides  (GOS) (5). However, it is not easy to find out which foods they are in because this information is rarely on the food label.

Although eating prebiotic-containing foods is good for your gut, specific recommendations are not available. This means we can not advise you on a specific amount you should have per day.

Below is a list of foods that contain prebiotics (6):

Vegetables	Fruit	Starch	Beans & Nuts
Artichoke	Apple	Wholemeal and White Bread	Almonds
Leek	Pomegranate	Granola	Baked Beans
Onion	Raisins	Muesli	Kidney Beans
Garlic	Prunes	Pearl Barley	Soya Beans
Beetroot		Couscous	Silken Tofu
		Wheat Bran	Butter Beans

HOW MUCH PREBIOTICS SHOULD I EAT PER DAY?

Although eating prebiotic-containing foods is good for your gut, specific recommendations are not available. This means we can not advise you on a specific amount you should have per day.

PREBIOTIC SUPPLEMENTS

There are several prebiotic supplements on the market, which can have beneficial effects on your gut health, as long as you pick the correct type and dose.

Most research looks at supplements that contain galactooligosaccharides (GOS). These specifically target the growth of good gut bacteria – bifidobacteria (7).

In a study comparing ederly people to non-ederly adults, a trial of GOS supplements increased levels of bifidobacteria for both groups (9). This finding is important as lower levels of bifidobacteria and bacterioide have been linked to IBS (8).

In a further study of 69 IBS patients GOS supplements combined with the low fodmap diet found that IBS symptoms reduced. However, contradicting the study above, this study found that GOS supplements did not reduce bifidobacteria. 

Therefore, the research findings at the moment are contradictory and there cannot be one set recommendation. 

PREBIOTICS IN IRRITABLE BOWEL SYNDROME

In short, prebiotics do not help IBS systems, however they do have an impact on your microbiome in your gut.

A study conducted in 2009 found that using GOS improved stool consistency, bloating, flatulence and anxiety when 3.5g/day of GOS was taken. It was thought to have this effect by increasing levels of bifidobacteria & lactobacilli (10).

In a different trial cooking symptom improvement using prebiotics, no symptom improvement in IBS was found however there was an improvement in bifidobacteria (12).

However, a meta-analysis* study in 2019, found that although bifidobacteria levels are seen to increase with prebiotics (both supplement and food), IBS symptoms do not improve. (11). 

*A meta-analysis is a type of study that looks at multiple previous studies and collates the results to find an overarching result. THis is considered to be more accurate because it includes multiple studies and therefore more participants and different researchers. 

THE LOW FODMAP DIET AND PREBIOTICS

The low FODMAP diet restricts the intake of prebiotics as mostFODMAPs are prebiotics. 

This is one reason why the low FODMAP diet restriction phase should only be temporary and it is not good for your gut health long term. You can read more on the low FODMAP diet here. 

Research has shown that taking a probiotic supplement whilst on the low FODMAP diet will help to improve levels of gut bacteria which would have otherwise been reduced due to the lack of prebiotics in the diet (10).

Here are some Low FODMAP prebiotic foods:

• Banana (unripe)
• Common or red cabbage
• Kiwi fruit
• Canned lentils
• Canned chickpeas 
• Oats

IS THERE ANY HARM IN TAKING PREBIOTICS?

Potentially, yes. Please take on board the following:

If you have digestive symptoms and are considering trialing prebiotics through diet or supplement, please ensure you have a proper medical diagnosis first.

If you have been advised by your GP or dietitian to take prebiotics, do this slowly. Prebiotics are fermented by gut bacteria and which gives off gas. If you increase too quickly and your gut is sensitive, you may get some unpleasant gut symptoms.

Care must be taken if using a GOS or fructo-oligosaccharide prebiotic supplement. It’s important to take the specific prebiotic that will improve gut bacteria related to IBS symptoms and high doses are linked to worsening symptoms (6).

Please consult your doctor or registered dietitian to include prebiotics into your diet safely.

SUMMARY

Having a variety of prebiotic sources in your diet is important for your overall gut health. You can find prebiotics in food and supplements.

Taking prebiotic supplements when you do not have any digestive health symptoms may improve your good gut bacteria levels, but what exact benefit this results in, is currently unknown.

Updated by Maiya Bahra Student Dietitian (2022), reviewed by Serena Bansal Registered Dietitian BSc Hons, and Kirsten Jackson Consultant Dietitian BSc Hons, RD, PG Cert