The "live active cultures" in yogurt may sound like a good source of probiotics, but there's no guarantee they contain enough of those good bacteria to benefit your health.
Photo by Indi Samarajiva
Although good bacteria are critical to health, scientists are still trying to understand which probiotics work and how well. If you'd like to try probiotics, you're better off buying supplements like pills instead of assuming you can get the dose you need from yoghurt. Melinda Wenner-Moyer explains at Slate:
if your reaction to all this is whatevs, I'll just feed my kids yoghurt, you should know that Sonia Michail, a pediatric gastroenterologist at Children's Hospital Los Angeles, told me that although it can be healthy, yoghurt is "not a consistent or reliable source for probiotics." Even if yoghurt leaves the factory teeming with bacteria, the low pH of the mixture may kill them: A 2010 study found that after 10 days in the fridge, 70 per cent of the probiotics in various types of yoghurt had died. Indeed, while many yoghurt brands tout that they contain "live active cultures," they generally don't say how many are there, and research suggests that foods need to provide between 106 to 108 live cultures per gram — that's a massive amount — to have a beneficial effect.
Supplements that have been used in studies, with good results, include Culturelle and Florastor to counteract diarrhoea from stomach bugs. There's a more complete list of what bacteria have been shown to help with various illnesses in Table 1 of this paper from the Journal of Clinical Gastroenterology. Check out the link below for more on probiotics, including the question of whether they're good for healthy kids.