The short answer: probiotics are live, helpful microbes. Prebiotics are the food that helps your helpful microbes grow. One adds players to the team, the other feeds the team you already have. They do different jobs, and they work well together.
Prebiotic vs probiotic at a glance
| Probiotics | Prebiotics | |
|---|---|---|
| What they are | Live microorganisms, usually bacteria and sometimes yeast, that benefit your health when you get enough of them | Substances, mostly types of fiber, that your gut microbes feed on, to your benefit |
| Alive? | Yes, so the strain, the dose and how the product is stored all matter | No. There's nothing to keep alive |
| Where you find them | Supplements, and some foods with live cultures such as yogurt (zabadi) | Onions, garlic, leeks, bananas, oats, barley, beans, peas, artichokes, plus added fibers such as resistant dextrin and inulin |
| What to look for on a label | Named strains and the number of live cultures | The type of fiber and how many grams you get |
| Think of them as | New seeds for the garden | Water and fertiliser for what's already growing |
What are probiotics?
Probiotics are live microorganisms that benefit your health when you take them in adequate amounts. That's the essence of the definition scientists have used since an expert group convened by the FAO and the World Health Organization set it out in 2001. The ones you'll see most often belong to the Lactobacillus and Bifidobacterium groups of bacteria, along with a yeast called Saccharomyces boulardii.
Two details matter more than most people realise:
- Strain and dose. The benefits of a probiotic depend on the exact strain and how much of it you get. A probiotic isn't a generic ingredient. It's a specific microbe, tested for a specific effect.
- Fermented food isn't automatically probiotic. Fermented foods do contain live microbes, but usually in unknown types and amounts, so experts don't count most of them as proven probiotics. They can still be a good part of your diet.
What are prebiotics?
Prebiotics aren't alive. The international expert panel that defines the term (ISAPP) describes a prebiotic as something your gut microbes selectively use, and that benefits your health as a result.
In practice, most prebiotics are types of fiber, although not every fiber is a prebiotic. You can't digest them, so they pass through your stomach and small intestine and reach your large intestine intact. There, your gut bacteria ferment them and produce short-chain fatty acids along the way.
For a closer look at one prebiotic fiber and how it ends up in a drink, read what is prebiotic fiber water?
Where do you find them in everyday food?
You're probably eating some of both already.
- Prebiotics: onions, garlic and leeks, bananas, oats, barley and whole wheat, beans (yes, that includes ful), peas, cabbage, eggplant, artichokes and asparagus.
- Probiotics: yogurt (zabadi) and other foods made with live cultures, plus probiotic supplements. Look for the words "live cultures" on the label.
Do you need both?
They're a natural pair. Probiotics bring in helpful microbes, and prebiotics feed the helpful microbes that are already there. Products that combine the two even have their own name: synbiotics.
If you're wondering where to start, fiber is a sensible first step. Most of us simply don't eat enough of it. The World Health Organization recommends at least 25 g a day for adults, and research suggests most people worldwide eat less than 20 g. Feeding the bacteria you already have is often the easier win. Our guide to how much fiber you need a day shows how to get there.
Are there any downsides?
- Prebiotics and fiber: adding a lot of fiber too quickly can cause gas and bloating. Increase gradually over a few weeks and drink plenty of fluids.
- Probiotics: they have a good safety record in healthy people. The risks are higher for premature infants and for people with a weakened immune system or a serious illness, who should speak to a doctor before taking them.
Where does Good Inside fit?
Good Inside is a prebiotic, not a probiotic. Each 500 ml bottle has 5 g of resistant dextrin, a prebiotic fiber that helps nourish beneficial gut bacteria, with zero sugar and just 7 calories.
There are no live bacteria in the bottle, so there's nothing to keep alive. It has a 12-month shelf life and doesn't have to stay in the fridge, although it tastes best cold. If you're looking for where to buy it and what it costs, see our guide to prebiotic water in Egypt.
Quick questions
Can I take prebiotics and probiotics together?
Yes. You can take a product that combines them, or simply have fiber-rich foods and yogurt in the same day. If you have a health condition, check with your doctor first.
Is yogurt a prebiotic or a probiotic?
Yogurt with live cultures sits on the probiotic side, because it contains live bacteria. It isn't a prebiotic. Pair it with a banana or some oats and you've got both.
Does prebiotic water contain live bacteria?
No. Prebiotic fiber water contains fiber, not bacteria. It feeds the good bacteria you already have.
Is all fiber prebiotic?
No. Most prebiotics are fibers, but only fibers that your gut microbes selectively use, with a benefit to you, count as prebiotic. Other fibers are still good for you in different ways, such as adding bulk and keeping you regular.
Sources
- International Scientific Association for Probiotics and Prebiotics (ISAPP): the consensus definition of a prebiotic
- ISAPP: probiotics, strains, doses and fermented foods
- Frontiers in Microbiology: how the definition of probiotics developed, from FAO/WHO (2001) to ISAPP (2014)
- Global Prebiotic Association: resistant dextrin and how it is fermented
- US National Center for Complementary and Integrative Health: probiotics, usefulness and safety
- Children's Hospital of Philadelphia: prebiotic foods
- World Health Organization: updated guidelines on carbohydrates, including fiber (2023)
- The Lancet: fiber intake and health, a review commissioned by the WHO (2019)
- Mayo Clinic: dietary fiber, essential for a healthy diet
This article is for general information and isn't medical advice. If you have a health condition or take medication, talk to your doctor before changing your diet.
Want the prebiotic half sorted? Shop Good Inside packs.
