What is the difference between probiotics and postbiotics?
Probiotics are live bacteria; postbiotics are dead or inactivated variants of them. Postbiotics are safer and more stable, but whether they also work better clinically has not yet been sufficiently studied in humans.
Probiotics are live bacteria that, when taken in sufficient amounts, confer health benefits. They are active, living cells that reach the gut and get to work there. Postbiotics are the opposite: dead or inactivated micro-organisms, or fragments and by-products of them. The official definition (from an international scientific organisation dedicated to probiotic research) states that postbiotics must confer a health benefit without the involvement of living cells. That definition is not yet fully agreed upon, however: scientists do not always concur on exactly what does and does not fall under it.
The biggest practical difference lies in safety and stability. Live bacteria carry small risks: in theory they can cross the gut wall, transfer antibiotic resistance, and they die off if stored incorrectly. Postbiotics do not carry those risks. This makes them regarded as safer for vulnerable groups, such as infants, older adults, and people with a weakened immune system. They are also more stable during storage and transport.
Postbiotics contain bioactive compounds that also play a role in live bacteria, but are already present without the bacterium itself needing to be active. These include short-chain fatty acids (such as butyrate and propionate), which strengthen the gut wall and improve insulin sensitivity, as well as enzymes and protein fragments that regulate immune defences. Much of what we know about this comes from cell and animal research; clinical evidence in humans is still limited.
Interestingly, probiotics do not always have a favourable outcome. Laboratory research on human intestinal tissue showed that under certain conditions they can also act in a pro-inflammatory manner, even in people with intestinal inflammation. Postbiotics, by contrast, protected that same tissue against inflammation, including after exposure to a pathogen such as Salmonella. These are preliminary laboratory findings, not proof that this is always how things work in practice.
In metabolic diseases such as overweight and type 2 diabetes, both probiotics and postbiotics appear to have beneficial effects, but the best combinations and doses are not yet known. In teenagers with metabolic syndrome, no clear effect has been demonstrated for probiotics, prebiotics, or synbiotics; for postbiotics in young people, virtually no research exists.
This answer is based on several review articles and one laboratory study on human intestinal tissue. The definition of postbiotics has been described by an international scientific consensus group but has not yet been universally accepted. Clinical studies on the effects of postbiotics are scarce; most findings on mechanisms of action come from cell and animal research. The review authors themselves emphasise that optimal doses and formulations have not yet been established, and that evidence for specific applications in humans is largely lacking.
Do prebiotics -- the fibres that feed your good bacteria -- work just as well as probiotics?
Prebiotics and probiotics are comparably effective for some complaints, but probiotics appear to have a slight advantage for depression and blood sugar. Switch supplements or combine them only once you know which complaint you want to address, and focus first on getting more fibre through ordinary food.
How much probiotic do you need per day?
There is no universal daily dose for probiotics: how much you need depends strongly on the bacterial strain, the application, and your specific complaint. Always choose a product that has been studied specifically for your situation, and when in doubt consult your doctor or pharmacist.
Can probiotics improve your health in later life?
Probiotics can make a modest contribution to your health in later life, but which product works best depends on what you want to improve. For cognitive health there are initial positive results, for fighting infections and managing cholesterol there are somewhat more indications, but convincing large-scale evidence is still lacking.
Do probiotics help with irritable bowel syndrome itself, or only when taken alongside antibiotics?
Probiotics reduce irritable bowel symptoms without antibiotics, with Bacillus coagulans and Bifidobacterium strains having the strongest supporting evidence. Choose a specific product containing one of these strains and give it at least 4 to 8 weeks.
Do probiotic pills actually help your gut?
Probiotics genuinely help, but not for everything and not equally with every pill. The evidence is strongest for antibiotic-associated diarrhoea and irritable bowel syndrome; for Crohn's disease, they demonstrably do not work.
Are fermented foods and probiotics good for your gut?
Fermented foods, particularly yoghurt and kefir, show positive indications for gut health; for most other products such as kimchi and kombucha, this has not yet been demonstrated in humans.