The bacteria in your gut come from food, the long-term fix is to eat a better diet. Unfortunately, this is quite confusing for most people because you can't see the microbiome in your food, and the only practical way to sense what kinds of bacteria you're promoting with your diet, is to ask yourself "how do you feel" which can be affected by all sorts of unrelated things. I mean, most people don't even really think about how they feel, they wouldn't be able to answer the question.