This information on Probiotics is from Dr Joel Fuhrman’s book “Super Immunity”. I can’t recommend this book highly enough. I have it on my ipad using the Kindle app.
Also take a look at the section Did You Know? on this blog for further valuable well researched information.
The term “probiotics” is used both for the beneficial bacteria that are native to our intestinal tract and for supplemental live bacterial organisms that are thought to be beneficial when ingested. However, the (limited) bacteria in supplemental probiotics and fermented foods are not the same as the indigenous bacterial flora that live in the gut. Supplemental probiotics serve a beneficial role—but mostly when the normal native bacteria have been harmed or removed with antibiotic use or perverted with a diet of sweets and processed foods.
There is no published evidence that probiotic supplements are able to effectively replace all the functions of the body’s natural flora when these have been killed off. Probiotics are useful after taking antibiotics, as noted; but it can still take months to reestablish the normal type and amount of gut flora. Healthy foods promote healthy bacteria to live in the gut; unhealthy foods promote unhealthy bacteria and yeast forms. However, unless a healthy diet, rich in various fibers, is continually maintained, the probiotic bacterial levels achieved by supplements drop within days when supplementation ceases. So what we eat is still the most important factor in maintaining our intestinal flora.
“Good” bacteria feast on fiber and resistant starch, while “bad” bacteria and yeast feast on refined sugar and animal fat. There is no substitute for a healthy diet; and if you are eating health-promoting foods and avoiding junk foods and antibiotics, it is not necessary for you to take probiotics or fermented foods. Your body will grow the right kind of bacteria automatically.
Fuhrman, Joel (2011-09-20). Super Immunity: The Essential Nutrition Guide for Boosting Your Body’s Defenses to Live Longer, Stronger, and Disease Free