Understanding Prebiotics, Probiotics and Postbiotics.

Interest in gut health and the human microbiome is booming, but the jargon can be confusing. In simple terms, probiotics are the live beneficial microbes we consume; prebiotics are the foods (mostly fibres) that feed those microbes; and postbiotics are the helpful by-products the microbes produce.

Prebiotics, Probiotics and Postbiotics: A Complete Guide to Gut Health

Think of making a sourdough starter: you add flour (the prebiotic food) and water to a jar. Wild yeasts and bacteria (the probiotics) begin to grow. Over days they ferment the flour, producing acids (the postbiotics like lactic acid) that make the starter sour. These acids help sustain a balanced microbial community. In your gut, a similar process happens – you eat plant fibres and polyphenols (prebiotics), which fuel beneficial microbes (probiotics). The microbes then produce short-chain fatty acids and other molecules (postbiotics) that support your health. A scientific consensus defines probiotics as “live microorganisms that… confer a health benefit” when eaten, prebiotics as “substrates that are selectively utilized by host microorganisms conferring a health benefit,” and postbiotics as preparations of non-living microbes or their components that benefit the host.

Prebiotics: The “Fuel” That Feeds Beneficial Gut Bacteria

Prebiotics are typically plant-derived fibres and compounds that resist our own digestion but are fermented by gut microbes. They act like selective fertiliser for good bacteria such as Lactobacillus, Bifidobacterium, and Akkermansia. Feeding these microbes helps them flourish, producing metabolites (like short-chain fatty acids) that reduce inflammation and nourish the gut lining. A broad range of prebiotic compounds exist, including inulin, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS). In practice, a diet high in varied plant fibres promotes microbial diversity, which is generally linked to better health. In contrast, low diversity (microbial “dysbiosis”) is associated with conditions like obesity, type 2 diabetes, inflammatory bowel disease, and even mood disorders.

Prebiotic Foods

Whole grains (oats, wheat, barley, rye)
Pulses and legumes (beans, lentils, chickpeas)
Vegetables like onions, garlic, leeks, asparagus, and chicory
Bananas and other fruits

Polyphenol-rich Foods

Berries (blueberry, cranberry), red grapes
Green tea/oolong, coffee, and cacao

Fibre Targets

Aim for 25–35 g of fibre daily from a variety of plants
Gradually increase intake if your diet is low in fibre (15–20 g)

Probiotics: Live Cultures to Support Your Gut Microbiome

Probiotics are the living microbes (bacteria or yeasts) that can benefit our gut when we eat them in sufficient amounts. By occupying space and consuming nutrients, probiotics help crowd out pathogens and prevent infections. Many also produce lactic or other acids, which naturally inhibit harmful microbes and support the gut barrier. Each strain has specific effects, such as relieving constipation, boosting immunity, improving mood, or regulating blood sugar.

Clinically, dozens of trials show that probiotics can strengthen intestinal barrier function and reduce inflammation. A 2023 meta-analysis of 26 trials found that probiotic supplements significantly improved gut barrier measures and lowered inflammatory proteins. In practice, the easiest sources of probiotics are fermented foods. A ten-week study in healthy adults showed that eating more fermented foods steadily increased gut microbial diversity and decreased blood inflammation.

Fermented Probiotic Foods

Yogurt (especially with live cultures), kefir, probiotic cheeses
Fermented vegetables (sauerkraut, kimchi, pickles)
Fermented soy (miso, tempeh)
Sourdough bread

Probiotic Supplements

Multi-strain capsules with well-studied strains such as Biome Restore
Evidence-backed CFU for specific goals (immunity, mood, constipation)
Always follow product instructions for dosage

Postbiotics: The Health Benefits of Microbial By-Products

Postbiotics are the beneficial by-products and components of probiotics, including short-chain fatty acids (SCFAs), peptides, cell wall fragments, and even dead microbial cells. The ISAPP consensus defines a postbiotic as inactivated microbial cells (or their components) that still confer health benefits.

Examples and Benefits

SCFAs: acetate, propionate, butyrate – support gut barrier and colon cells
Peptides, cell wall fragments, dead microbial cells
Act as signaling molecules in gut–brain axis and vaginal microbiome

How to Get Postbiotics

Eat prebiotics (plant fibres, polyphenols) to feed gut microbes
Consume fermented foods (yogurt, kefir, sauerkraut, kimchi)
Optional: targeted postbiotic supplements under medical guidance (e.g., butyrate capsules)

Gut-Healthy Foods: A Biotic Shopping List

Variety of Plants

Eat a rainbow of fruits, vegetables, whole grains, herbs, and spices
Aim for 30+ different plant types per week
Target 25–35 g of fibre daily from vegetables, legumes, whole grains

Daily Fermented Foods

Include at least one serving per day (yogurt, kefir, kombucha, sauerkraut, etc.)
Higher intake increases microbial diversity and lowers inflammation

Phytonutrient-rich Foods

Berries, greens, nuts, garlic/onion, tea, cocoa
Polyphenols boost key gut bacteria (e.g., Akkermansia)

Limit Processed Foods

High sugar/fat, low fibre diets reduce beneficial bacteria
Minimise ultra-processed foods

Mindful Supplementation

Consider evidence-based supplements if needed (prebiotic fibre powders, probiotic strains)
Priority is always food first

Gut microbiome science is evolving rapidly, but the bottom line for wellness is clear: eating a variety of plant fibres and fermented foods feeds beneficial bacteria (prebiotics & probiotics) and yields valuable metabolites (postbiotics). This triad supports a resilient gut barrier and balanced immunity, promoting overall health from digestion to mood.

Sources: Authoritative reviews and clinical studies outline the definitions and roles of prebiotics, probiotics, and postbiotics, and their effects on human health.