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.
For antibiotic-associated diarrhoea, probiotics are well supported by evidence. Taking them at the same time as antibiotics reduces the risk of that diarrhoea by an average of 37%. The effect is larger at higher doses, but no difference was found in people who already had a low risk of diarrhoea to begin with. Bacteria from the Lactobacillus and Bifidobacterium families appear to have the greatest effect.
For irritable bowel syndrome (IBS), probiotics also show positive results. The chance of symptom improvement is almost twice as high with probiotics as with a placebo. Which specific bacterial strain works best, however, is not yet clear. Notably, combinations of pre- and probiotics together showed no significant improvement in IBS.
For constipation, the picture is more mixed. A study in 250 adults showed that a probiotic formula improved stool consistency, but bowel movement frequency did not change significantly. Evidence in humans for the underlying mechanism in constipation is still thin; much of what we know comes from animal research.
Probiotics clearly do not work for all gut complaints. For Crohn's disease and acute pancreatitis, no benefit has been demonstrably shown. This is important, because someone with symptoms does not want to take something for years that does not help.
Safety is not an issue for most people, but a caveat applies to those with a severely weakened immune system. Because probiotics contain live bacteria, there is a small but real risk of infection. Always discuss their use with a doctor in that case. Another practical point: not every probiotic pill is the same. The strain, the dose and the condition determine whether there is any effect.
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 humans.
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.
Can probiotics improve your health in later life?
Probiotics may offer specific benefits for older adults, such as a better immune response and less constipation, but which strain, dose and person this applies to is not yet precisely known. Discuss it with your doctor if you have chronic complaints that fit the profile.
Do prebiotics, the fibres that feed your good bacteria, work just as well as probiotics?
Prebiotics alone are less effective than probiotics in the best-studied situations. For diarrhoea or immune support, probiotics are more useful, but even those effects are smaller than often assumed.
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.
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.