New scientific study has demonstrated a connection between mental health and the balance of bacteria in the stomach. Did you know that your intestines are home to trillions of bacteria? Yes – although in one sense you are an individual, you are also an entire ecosystem. 😉 It’s ok: Gut bacteria play an important role in maintaining homeostasis or balance in the body. There are “good” bacteria that help keep the body functioning at optimal levels – and if these are compromised it can not only weaken the body against pathogens, but also alter the body’s fundamental chemistry in ways that influence wellbeing on a deep level.
Probiotic strains of bacteria have been proven to have beneficial effects on health, which contributes to the increase in probiotic drinks and snacks in the market. However, gut bacteria are greatly affected by our diet – as well as by accidental consumption of pathogenic (harmful) strains. When gut bacteria are altered, it can also have drastic effects on health. 
Read more at herbs-info.com