We report 50 “good” and 50 “bad” bacteria, which we have identified as having the strongest correlations with health based on data from tens of thousands of other ZOE members.

Your gut microbiome also contains many other bacteria, which have weaker correlations with health. That is why the percentages of the 50 “good” and 50 “bad” bacteria add up to less than the full 100% of all bacteria in your gut.