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Pre and probiotics work as a pair. Prebiotics are types of fibre that your own gut bacteria use as food, found in everyday ingredients such as onions, garlic, leeks, oats, slightly green bananas and pulses. Probiotics are live bacteria, found in foods such as natural yoghurt and kefir or in supplements. A diet rich in prebiotic fibre feeds the bacteria you already have, which is why food is the best place to start.
This guide explains the difference between the two in plain language, shows which British supermarket staples contain them, gives ideas for simple meals, and explains where supplements fit in.
In short
- Prebiotics are fibres such as inulin that gut bacteria use for energy, while probiotics are live microorganisms.
- Onions, garlic, leeks, oats, bananas, beans, lentils and wholegrains are everyday sources of fermentable fibre.
- Natural yoghurt and kefir are the most familiar foods with live cultures.
- Increasing fibre slowly and drinking enough helps avoid wind and bloating.
- Combining both in your meals is simple and does not require special products.
What is the difference between prebiotics and probiotics?
The two words sound almost the same, which causes a lot of confusion. A probiotic is a live microorganism. The fact sheet of the US Office of Dietary Supplements uses the internationally agreed definition: live microorganisms that, when given in adequate amounts, provide a health benefit to the host. A prebiotic is not alive. The same fact sheet describes prebiotics as complex carbohydrates, such as inulin, that gut microbes use for energy.
A simple way to remember it is to think of a garden. Probiotics are like new plants added to the soil, while prebiotics are the compost that feeds the plants already growing there. Your large intestine already contains a huge community of bacteria. Feeding them well with fibre is just as important as adding new ones, and often more so.
How does fibre feed your gut bacteria?
When you eat fibre, your small intestine cannot break it down, so it travels on to the large intestine. There, bacteria ferment some types of fibre. In the process they produce gases and substances called short-chain fatty acids, which are used by the cells lining the gut. The German health institute IQWiG explains on InformedHealth.org that gut bacteria feed on undigested food, help the large intestine absorb vitamins, produce some B vitamins and vitamin K themselves, and make it harder for harmful bacteria to settle.
Not all fibre behaves in the same way. Some types, such as those in wheat bran, mainly add bulk. Others, such as inulin and the fibres in oats and pulses, are fermented more readily. Eating a wide variety of plant foods gives your gut bacteria a wider variety of food, which is one reason dietitians often recommend aiming for many different plants each week.
The gas produced during fermentation is the reason why a sudden jump in fibre can cause wind and bloating. Your gut adapts over a few weeks, so the trick is to increase fibre gradually.
Which everyday foods contain prebiotic fibre?
You do not need special products to eat prebiotic fibre. Many ingredients that are already in British kitchens contain it. The table gives an overview and ideas for using them.
| Food | Type | Easy ways to eat more |
|---|---|---|
| Onions, leeks, spring onions | Prebiotic fibre (inulin-type) | Base for soups, stews, sauces and omelettes |
| Garlic | Prebiotic fibre (inulin-type) | Add to tomato sauces, dressings and roasted vegetables |
| Oats | Soluble fibre (beta-glucan) | Porridge, overnight oats, oat-topped crumbles |
| Bananas, especially slightly green | Resistant starch and fibre | Sliced on porridge or eaten as a snack |
| Beans, lentils, chickpeas | Fermentable fibre | Add to soups, curries, chilli or salads |
| Wholegrain bread, pasta, barley | Mixed fibre | Swap for white versions gradually |
| Cooked and cooled potatoes or rice | Resistant starch | Potato salad, rice salad |
| Asparagus, chicory, Jerusalem artichoke | Prebiotic fibre (inulin-type) | Seasonal side dishes and salads |
The UK recommendation for adults is 30 grams of fibre a day, and the European Food Safety Authority considers 25 grams a day sufficient for normal bowel function. Most people do not reach these amounts, so adding a few of the foods above to your weekly shopping is a sensible first step.
Which foods contain live cultures?
Live cultures are found in fermented foods that have not been heat-treated after fermentation. In the UK, the most familiar examples are natural yoghurt labelled with live or active cultures, and kefir, a fermented milk drink that has become widely available in supermarkets. Some cheeses, unpasteurised sauerkraut, kimchi and miso also contain live microorganisms.
It is worth knowing what the US Office of Dietary Supplements points out: yoghurt can contain probiotic bacteria, but many fermented foods with live cultures, such as kimchi, kombucha and sauerkraut, typically do not contain strains that have been studied for specific effects. That is not a reason to avoid them. They are tasty, nutritious foods that add variety to your diet. It simply means they should be seen as good food rather than as a treatment.
When you buy yoghurt or kefir, choose plain versions where possible. Flavoured products often contain a lot of added sugar, and you can add your own fruit, oats or a little honey instead.
How can you combine both in everyday meals?
Combining prebiotic and probiotic foods in one meal is easy and often happens naturally. Here are a few ideas that fit a normal British week.
- For breakfast, porridge made with oats and topped with sliced banana and a spoonful of natural yoghurt combines fibre with live cultures.
- For lunch, a lentil and vegetable soup with onion, leek and garlic, served with wholegrain bread, is rich in fermentable fibre.
- As a snack, a glass of kefir with an apple or a handful of nuts works well between meals.
- For dinner, a bean chilli or a chickpea curry with brown rice and a dollop of yoghurt on top brings both together.
- At the weekend, a potato salad made with cooled boiled potatoes and a yoghurt dressing is an easy side dish.
If you are new to high-fibre eating, introduce these changes one at a time over two or three weeks and drink enough water. If you find that wind and bloating become a problem, our article on bloating after eating explains how to adjust, and the guide to gut health supplements and realistic hopes puts supplements into context.
Do you need pre or probiotic supplements?
Most people can get plenty of prebiotic fibre from food, and many enjoy fermented foods as part of their diet. Supplements can be an option if you find it hard to eat these foods regularly, or if you want to try a specific product after reading its label. The effects of bacterial cultures depend on the exact strain, and no health claim for probiotics or prebiotics as such has been authorised in the UK or the EU, so no product can promise a particular benefit.
If you would like to try a supplement, choose one with clearly named strains, a stated count of live bacteria and storage instructions. In the LR range there are PRO 12+ capsules with bacterial cultures, and the label and our product page give the details of what they contain. A capsule is an addition to a fibre-rich diet, not a substitute for it. Other daily products are in our supplements category.
The product mentioned above:
When should you see a doctor?
Changing your diet should make you feel comfortable, not unwell. Speak to your GP if you have a change in bowel habits lasting more than three weeks, blood in your stool, unexplained weight loss, or tummy pain and bloating that do not go away. If you have a diagnosed bowel condition, such as irritable bowel syndrome or inflammatory bowel disease, ask your GP or a dietitian before making big changes to your fibre intake, because some people need a tailored approach. If you are pregnant, have a weakened immune system or a serious illness, check with your GP or pharmacist before taking culture supplements.
Frequently asked questions
Can I eat prebiotic and probiotic foods at the same meal?
Yes. There is no reason to separate them, and many traditional dishes already combine them, such as porridge with yoghurt or a bean stew with a yoghurt topping.
Are bananas a good prebiotic food?
Bananas contain fibre, and slightly green bananas contain more resistant starch, which reaches the large intestine undigested. Ripe bananas are still a good source of fibre and easier to digest for some people.
Is shop-bought sauerkraut a source of live cultures?
Many jarred sauerkraut products are pasteurised, which kills the bacteria. Look for refrigerated products labelled as unpasteurised or containing live cultures if that matters to you.
Why do onions and garlic make me bloated?
They contain fibres that gut bacteria ferment quickly, which produces gas. Cooking them, eating smaller amounts and increasing them gradually often helps. If they cause strong symptoms, speak to your GP or a dietitian.
Sources
- NIH Office of Dietary Supplements: Probiotics fact sheet for health professionals
- InformedHealth.org (IQWiG): How does the intestine work?
- InformedHealth.org (IQWiG): What are microbes?
- EFSA: Dietary reference values for carbohydrates and dietary fibre (2010)
Food supplements are not medicines and do not replace a varied, balanced diet and a healthy lifestyle. This article is general information and not medical advice; if you have symptoms or take medication, please speak to your GP or pharmacist.