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.
Yes, probiotic pills genuinely help, but only for the right condition and with the right bacterium. The evidence is strongest for antibiotic-associated diarrhoea: taking probiotics at the same time reduces the risk by an average of 37%. Choose a capsule or powder containing Lactobacillus or Bifidobacterium strains, listed on the label as a species name together with the number of CFU (live bacteria) per dose. Choose the highest dose the product offers and take it throughout the entire antibiotic course. If your personal risk of diarrhoea is low to begin with, there is no evidence that it helps and it is not worth the money.
For irritable bowel syndrome (IBS) it is also worth trying: in research, the chance of improvement is almost twice as high as with a placebo. Use a capsule, powder or drops containing live bacteria, 1 × 10⁹ to 4 × 10⁹ CFU per day, for at least 4 to 8 weeks. Which strain works best has not yet been established; the level of the dose proved less important in research than the duration of treatment. Check the label for Lactobacillus, Bifidobacterium, Bacillus or combination preparations. Because IBS is a medical condition, discuss this with your doctor. A combination of probiotics and prebiotics (food for the bacteria) showed no significant advantage over probiotics alone in IBS.
For constipation, it is worth trying cautiously. One study in 242 adults showed that a mix of Bifidobacterium animalis subsp. lactis HN019 and Lacticaseibacillus rhamnosus HN001, taken for at least 4 weeks, softened stools. How often you visit the toilet did not change. The CFU dose is not stated on the packaging of the products studied; make sure the label does specify the exact strains. That study was sponsored by the manufacturer, which makes the evidence less robust.
For Crohn's disease and pancreatitis, probiotics demonstrably do not work; do not use them for those conditions. A note of caution applies to people with a severely weakened immune system: because probiotics contain live bacteria, there is a small but real risk of infection. Always discuss use with your doctor in that case.
The answer draws on several large summaries of dozens of studies, including a review of 42 studies involving more than 11,000 participants on antibiotic-associated diarrhoea, and a network meta-analysis of 54 studies on irritable bowel syndrome. For constipation, human evidence is more limited: one randomised study in 250 adults and otherwise mainly animal research. The researchers rate the quality of the evidence for the strongest applications (diarrhoea, IBS) as high, but emphasise that differences in strain and dose have a large influence on outcomes.
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.
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.
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.
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.
Does eating flaxseed help your gut?
Through its fibre and lignans, flaxseed has a plausible positive effect on the gut, but for the gut as a specific target the evidence in humans is still limited. If you want to take concrete action, opt for at least 30 grams of ground flaxseed per day.