Your gut is full of bacteria that help keep you healthy. But those bacteria need to eat too. That is exactly what prebiotics do: they feed the beneficial microorganisms in your digestive tract. And they're found in foods you already know — you just need to know what to look for.
Key takeaways
- Prebiotics are indigestible fibers that stimulate the growth of beneficial gut bacteria — they are literally food for your microbiome.
- The richest sources are garlic, onion, leek, asparagus, banana, chicory, and artichoke.
- Prebiotics and probiotics work complementarily: prebiotics feed the bacteria that probiotic foods deliver.
- Most people eat too little fiber and therefore too few prebiotics — the average Dutch adult falls well short of the recommended 30g per day.
- Adding more prebiotic fiber is easiest by incorporating onion, leek, or garlic into daily meals.
What exactly are prebiotics?
Prebiotics is a collective term for substances — primarily indigestible fibers — that are used as food by specific bacterial strains in the large intestine. The best-known are fructo-oligosaccharides (FOS) and inulin, which occur naturally in vegetables and fruit.
The distinction from probiotics is important:
- Probiotics are the live bacteria themselves (in yoghurt, kefir, supplements).
- Prebiotics are the nutrients that allow those bacteria to grow and thrive.
Together they are sometimes called "synbiotics." But you don't need to take them simultaneously for effect — consistent prebiotic food intake is already a solid strategy.
Which bacteria benefit from prebiotics?
Lactobacilli and bifidobacteria in particular — the bacterial strains also found in probiotic products — are stimulated by prebiotic fibers. When these bacteria ferment the fibers, they produce short-chain fatty acids such as butyrate, propionate, and acetate. These fatty acids are an energy source for the cells lining the intestinal wall and may contribute to healthy gut function.
This is also why prebiotics can sometimes cause gas and bloating — fermentation in the large intestine produces gases too. Start gradually if you're not used to high-fiber foods.
The best prebiotic foods
Prebiotics occur naturally in many everyday foods. The richest sources:
- Garlic — contains fructans and is one of the richest prebiotic sources by weight
- Onion — raw onion has more prebiotic effect than cooked; shallots and chives also count
- Leek — contains inulin and FOS; easy to add to many dishes
- Asparagus — green asparagus in particular contains inulin
- Banana — unripe banana contains more resistant starch; ripe banana still has prebiotic effect
- Chicory — the industrial source of inulin extracts; also used as a salad green
- Artichoke — earthy vegetable with high inulin content
- Oats — contain beta-glucan, a soluble fiber with prebiotic potential
Want to track how much fiber you get each day? With Moveno, you photograph meals and instantly see the fiber content. Combine that with the probiotics guide for a complete picture of gut health.
Prebiotics vs. probiotics: what is the difference?
| Prebiotics | Probiotics | |
|---|---|---|
| What | Indigestible fibers | Live microorganisms |
| Function | Feed gut bacteria | Add beneficial bacteria |
| Sources | Garlic, onion, leek, oats | Yoghurt, kefir, sauerkraut |
| Evidence | Good for fiber intake, microbiome support | Stronger for specific conditions |
For most people, the most practical approach is to eat more prebiotic vegetables and fruit (well-supported benefit for fiber intake) and regularly consume fermented products.
How much fiber do you actually need?
The Dutch Health Council recommends 30g of fiber per day for adults. The average Dutch adult gets around 20–22g — a shortfall of roughly 8–10g. Some of that fiber comes from prebiotic sources, but not all fiber is prebiotic.
A few easy ways to add more prebiotic fiber:
- Add half an onion to a stir-fry, soup, or sauce: +1–2g fiber
- Garlic through dishes: small amount, but prebiotic effect per clove
- Leek as a vegetable base: 100g leek delivers roughly 3g fiber
- Oat porridge for breakfast: combined with flaxseed you boost fiber considerably — see the flaxseed guide
Can you eat too many prebiotics?
A sudden, large increase in fiber intake — including prebiotic fibers — can cause stomach cramps, gas, or bloating. This is due to fermentation in the large intestine.
The solution: build up prebiotic foods gradually over a few weeks and drink enough water. Your microbiome will adapt.
There is no established upper limit for prebiotic intake in healthy people, but very high doses (via concentrated supplements) can cause discomfort in some individuals.
More prebiotic food, less fuss
You don't need to buy prebiotics in a bottle: they are simply found in garlic, onion, leek, and other everyday vegetables. The key is consistency — adding a few prebiotic ingredients to your regular meals every day.
Want to get a handle on your fiber intake and overall nutrition? With Moveno, you photograph your meal and instantly see what you're eating — fiber included.
Sources
- Voedingscentrum — Prebiotics — definition, sources, and mechanism of prebiotics
- Voedingscentrum — Fiber — explanation of dietary fiber and recommended daily intake
- Voedingscentrum — Microbiome — information on the gut microbiome and health
- RIVM — Dutch Food Composition Database (NEVO) — reference database for nutritional values
