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.

Many alternative modalities of healing look to acidophilus for a wide range of health benefits. In addition to basic digestive assistance, acidophilus is thought to help bolster the immune system as a whole. It is also thought to provide some relief from intestinal problems, such as diarrhea.

The fungal infection of Candida albicans, more commonly referred to as a yeast infection when it affects the genital area, is thought by some to be controlled by acidophilus. Since acidophilus occurs naturally in the genitals, and plays a role in warding off such infections, some people advocate topical treatment. The topical application of yogurt, which contains acidophilus, is thought by many to help relieve and ultimately cure a yeast infection. Oral ingestion is also recommended, either of yogurt, or of an acidophilus supplement.

Because antibiotics kill the so-called probiotics, such as acidophilus, as well as harmful bacteria, many people feel that an antibiotic regime can lead to outbreaks of numerous problems, including yeast infections. It is recommended by many to take supplements of acidophilus and eat acidophilus-rich foods for a period of time after completing a regimen of antibiotics.