Interest in probiotics is higher than ever in the United States, according to a 2008 article published in the journal "Clinical Infectious Diseases." The benefits of these “good bacteria” are well documented and include improved digestion and immune function, improved vitamin synthesis and reduced risk of diseases including Crohn's and ulcerative colitis.

Yogurt is a rich source of probiotics, but be careful: Not all yogurt contains probiotics. Most brands that do will advertise this fact on the label. Powerful strains of probiotics found in yogurt include lactobacillus and bifidobacteria. The more different strains of these bacteria, the better, so look for this information on the label and compare brands when possible. Though store-bought yogurt does contain probiotics, some of these bacteria are inevitably destroyed by the pasteurization process. For a product containing the most live and active cultures, making yogurt at home with raw milk is ideal.

Kefir is a product very similar to yogurt; it is usually made from milk but can be made with other liquids such as coconut milk or water. Kefir, though, has the advantage of being 99 percent lactose free, making it a good option for those who are lactose intolerant. Additionally, kefir is among the richest sources of probiotics available, with three times the amount of probiotics typically found in yogurt. It can be purchased in most grocery stores; however, to produce a kefir containing the highest levels of probiotics, raw milk is ideal.

Fermented vegetables are probiotic-rich foods that easily can be made at home. Some common examples that can be purchased at the grocery store include sauerkraut and pickles. However, you may not get much benefit from commercially fermented vegetables such as sauerkraut, because much of the healthy bacteria and enzymes in these foods have been destroyed. The fermenting process is simple and only requires salt, water, a jar and your choice of vegetables grown in healthy, organic, bacteria-rich soil.

Kombucha tea is produced by fermenting sweet black tea with a flat culture of bacteria and yeasts known as the kombucha mushroom. The result is a probiotic-rich beverage with dozens of reported health benefits, including boosting the body's immune system. The American Cancer Society acknowledges the widespread reports of such claims, but says that none are supported by science, and in fact warns that kombucha tea has caused complications and even death in a few cases.