The term acidophilus is used to describe a number of bacteria which help in human digestion. These bacteria include L. acidophilus, L. casei, L. bulgaricus, among others. Lactobacilus acidophilus is one of the bacteria found in these mixtures, but the term acidophilus usually refers to a combination of L. acidophilus with other beneficial bacteria.
Acidophilus is touted for its many health benefits, some of which have been known about for thousands of years. The bacteria is found naturally throughout the human body, and most likely made its way into a food long ago, beginning a cycle of natural fermentation which people eventually learned to artificially duplicate.
When acidophilus are placed in a sugar-rich environment, they begin to eat the sugars they find there. They then convert these sugars into various things, including lactic acid. This adds a distinctive taste, and lowers the pH of the food or liquid so that other flora do not find it as friendly an environment, helping to preserve the food. Yogurt is probably the most well-known of foods that make use of acidophilus, and it is very easy to notice the sour taste of the lactic acid when eating this food. Other foods that contain acidophilus include sauerkraut, kombucha, kinchi, kefir, and many other fermented food products.
Acidophilus can help protect the body against harmful bacteria, parasites, and other organisms. As it breaks down, it releases things such as hydrogen peroxide that create a toxic environment for unhealthy creatures in the body, helping to drive them out. It also plays an important role in digestion, helping to produce a number of chemicals which aid in the digestion process.