For people with irritable bowel syndrome, probiotics show a concrete effect on abdominal pain and bloating, as shown by an analysis of 43 studies with more than 5,500 participants. For healthy people without complaints, convincing evidence for general gut health benefits is lacking. The choice of the specific strain is decisive in this regard.
Whether a probiotic is worth taking depends almost entirely on why you want to take it. For people with irritable bowel syndrome (IBS) there is solid ground: a large analysis of 43 studies involving more than 5,500 participants showed that certain strains clearly reduce abdominal pain and bloating. That is not a vague 'good for your gut', but a concrete effect in a specific condition.
Are you taking it purely as daily maintenance, without any complaints? Then it is fair to say that the studies provide hardly any convincing evidence for that. The claims about improved immunity or a more general gut health in healthy people run far ahead of what research has demonstrated so far.
If you have IBS symptoms and want to try something, the choice of strain is the only thing that really matters: choose a product whose specific strain has been studied for your complaint, not a jar with an impressive number on the label. Probiotics are safe for most healthy people and simply available over the counter. If you are seriously ill or taking medications that suppress your immune system, have a quick word with your doctor before you start.
Moderate evidence, 1 source(s); the direction is likely but not firmly proven.