Probiotics are live microorganisms (bacteria or yeast) that are particularly well-suited to your digestive system. For example, lactic acid bacteria is a common probiotic that gives sourdough and yogurt their characteristic sour flavor. In your colon, lactic acid bacteria digest the sugar known as lactose and may even prevent inflammation and inhibit cancer.
However, there’s a catch. As you’ve seen, your large intestine is quite far down in your digestive system. For a probiotic to make it to its new home, it needs to pass through the inhospitable acidic environment of your stomach. Pharmaceutical companies are experimenting with special coatings that help probiotics make the hazardous journey intact, but in the meantime it’s hard to tell how effective probiotic-fortified foods really are.
Prebiotics are substances that your healthy, colon-dwelling bacteria like to munch on. Supply these bacteria with more prebiotics, and you can encourage a small population to grow. Prebiotics are naturally present in fruits and vegetables, but don’t expect to find any in a box of macaroni and cheese.
The bottom line is that both probiotics and prebiotics are based on valid nutritional science that recognizes the value of good gut bacteria. But their success as products is less clear, and it’s a good guess that you’ll get more benefit from a diet that emphasizes fruits and vegetables than one that focuses on convenience foods and nutritionally fortified drinks, no matter what miraculous new additives manufacturers toss in.
Source of Information : Oreilly - Your Body Missing Manual