Twenty-one volunteers were given a course of antibiotics and then split into three groups. The first group were left to let the microbiome recover without any interventions, the second group were given probiotics and the third were given a fecal transplant of their own gut bacteria which was collected before the antibiotic treatment. The study found that the probiotics easily colonized the gut of the second group, but worryingly, rather than aiding the return of the normal gut microbiome, the probiotics actually significantly delayed it for months compared to both the group that had no intervention and the people who received a transplant of their own gut bacteria.
The research also showed that while probiotics colonised the gastrointestinal tract of some people, the gut microbiome of others just expelled them. There was no way of telling from their stool sample which category people fell into. “Some people accept probiotics in their gut, while others just pass them from one end to the other,” says Elinav. They found that the probiotic colonisation patterns were highly dependent on the individual. That tells us that the concept that everyone can benefit from a universal probiotic bought from the supermarket is empirically wrong, he says.
For example, yogurt is made with two “starter” bacterial cultures — Streptococcus thermophilus and Lactobacillus bulgaricus — but these bacteria are often destroyed by your stomach acid and provide no beneficial effect, Dr. Cresci explains. Some companies, though, add extra bacteria into the product, so check the labeling and choose products with bacteria added to the starter cultures, she advises.
If you are seeking non-dairy yogurt options, there are several that contain live probiotic cultures. Yogurts made from rice, soy and coconut milk are available on the market and also contain added probiotics that can provide the same benefits. Other alternative sources of probiotics include eating fermented foods like Brewer’s yeast, miso, sauerkraut, or micro algae. Whatever the source, always look for “live and active cultures” on the label.