How many probiotics do you need per day?
For irritable bowel syndrome, 1 to 4 billion live bacteria per day, maintained for at least four to eight weeks, has been shown to work. How long you keep it up is more important than the exact amount.
There is no universal daily dose of probiotics. How much you need depends entirely on the goal and the specific bacterial strain. A dose that works for one strain and one complaint is useless for a different strain. Without that strain-specific information, no meaningful number can be given.
For irritable bowel syndrome, participants in studies received between 1 and 4 billion live bacteria per day, for at least four to eight weeks. How long you keep it up mattered more than the exact amount. Which bacterial strain or combination works best is still unclear. Discuss this with your doctor.
For antibiotic-related diarrhoea, higher doses appear to work better than low doses, but again no single number can be given that applies to every product. The effect was also only seen in people with a moderate or high risk of diarrhoea; for those at low risk, there is no evidence that probiotics do anything. Discuss this with your doctor if you want to know whether this applies to your situation.
For goals such as weight loss, cognition in older age, or extending lifespan, the evidence is currently too thin or too one-sidedly funded by commercial interests to base a recommendation on. Probiotics for depression have only been studied in very small studies; those results are nowhere near ready for a dosage recommendation.
Look at the label for the bacterial strain, not just the number of bacteria. A high number means nothing if that strain has not been studied for your particular complaint.
This answer is based on three overview studies that summarise the available literature on probiotics. The researchers themselves emphasise that strain-specific validation is lacking for most goals, and that there is therefore no universal minimum effective dose. For people with irritable bowel syndrome, additional information comes from many studies combined that specifically examined dose dependence. The certainty of the evidence has been rated as low to very low for most applications.
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.
What is the difference between probiotics and postbiotics?
Probiotics contain live bacteria; postbiotics work with inactivated micro-organisms or their building blocks. Postbiotics are more stable and carry none of the risks associated with live bacteria.
Do prebiotics work just as well as probiotics?
Prebiotics and probiotics are comparably effective for constipation; for depression and blood sugar, probiotics have a slight advantage, though the effects are small. Focus first on getting more fibre through ordinary food.
Can probiotics improve your health in later life?
Probiotics can make a modest contribution in later life, but which product works best depends on what you want to improve. For cognitive health there are early positive results; convincing large-scale evidence is still lacking.
Do probiotics help with irritable bowel syndrome itself, or only when taken alongside antibiotics?
Probiotics reduce IBS symptoms even without antibiotics, with Bacillus coagulans and Bifidobacterium strains having the strongest supporting evidence. Discuss this with your doctor and give it at least 4 to 8 weeks.
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 people.