What Are Prebiotics & Should You Be Taking Them?

What Are Prebiotics?

Prebiotics are non-digestible, food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and thus improve host health (1 ).

WHAT? I hear you say!…..

In other words, prebiotics are a form of fibre found in some foods, which have the ability to help your good gut bacteria to thrive. Prebiotics do this by acting as a food source for your gut bacteria, which then multiply in numbers. This helps to improve your health as gut bacteria plays such a vital role.

A change in normal gut bacteria is often seen in digestive health problems such as irritable bowel syndrome and Chron’s disease (23 ). The use of prebiotics is therefore suggested to be a good way to improve the levels of good gut bacteria.


How Can I Add Them To My Diet?

Prebiotics In Food

Prebiotics are mainly fructans, inulin or galacto-oligosaccharides (GOS) (1 ). However, it is not easy to find out which foods they are in because this information is rarely on the food label.

Whilst it is thought that eating a variety of prebiotic containing foods will be good for your gut health, giving specific recommendations is impossible at this stage. The reason for this is that each food contains entirely different amounts of prebiotics and so creating a study to give an exact recommendation is impossible. There are even differences in the prebiotic levels of the same food depending on how it is manufactured.

But, what I would say is that you should be aiming to include a variety of these foods into your diet on a daily basis (unless otherwise advised not to but a registered dietitian).

Below, is a handy list of foods which would have a prebiotic affect (Monash, 2017 ).

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

Prebiotic Supplements

There are a number of prebiotic supplements on the market, which can have beneficial affects on your gut health, as long as your pick the correct type and dose.

Most research looks at supplements which contain galacto-oligosaccharides (GOS). These specifically target the growth of good gut bacteria – bifidobacteria (2 ).

In a study of 40 elderly people, a trial of GOS supplements increased levels of bifidobacteria and bacteroides (4 ). This finding is important as lower levels of bifidobacteria and bacterioide have been linked to IBS (2 ).

In a further study of 48 overweight individuals who had no bowel problems, GOS supplements  not only increased levels of bifidobacteria but also reduced levels of b- proteobacteria (a type of pathogen which can cause disease) (5 ).

Prebiotics In Irritable Bowel Syndrome

There are few good quality studies available which show a beneficial affect of prebiotic supplement use in IBS.

One study, again using GOS,  showed to improve stool consistency, bloating, flatulence and anxiety when 3.5g/day of GOS was taken. It was thought to have this affect by increasing levels of bifidobacteria & lactobacilli (6 ).

A further study looked at the affect of 5g of fructo-oligosaccharide per day in IBS sufferers and successfully showed a reduction in symptoms (7 ).

In other trials looking at the use of oligofructose and fructo-oligosaccharide, no symptom improvement in IBS has been seen (8 , 9 ).

The Low FODMAP Diet and Prebiotics

The low FODMAP diet actually restricts the intake of prebiotics. This is why the low FODMAP diet restriction phase is only a temporary measure.

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 prebiotic in the diet (10 ).


  • If you have digestive symptoms and are considering trialling an increase in prebiotics through diet or supplement, please ensure you have a proper medical diagnosis first .


  • If you have the go ahead from your GP or dietitian to try increasing prebiotics, please do this slowly. Prebiotics are fermented by gut bacteria and in this process, gas is given off. If you have a a huge increase, and your gut is already sensitive, you may notice that you get some rather nasty gut symptoms.


  • As for IBS, while prebiotics are useful, care must be taken to use a GOS or fructo-oligosaccharide supplement and to avoid a dose of more than 3.5 – 5g /day. This is because, it is important to take the specific prebiotic that will improve the gut bacteria related to IBS symptoms, whilst avoiding high doses which are linked to worsening symptoms (6 2 ).


Having a variety of prebiotic sources in your diet is important for general gut health.

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 yet.

Those who suffer with IBS may benefit from a prebiotic supplement, but care should be taken to get the correct type and dose.


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