WebMD and the Global Healing Center website list several natural probiotic foods. Some of these foods include unpasteurized sauerkraut, soft cheeses, green pickles, kimchi and kefir.
The Global Healing Center also lists ocean-based microalgae such as spirulina and blue-green algae. One of the most commonly known natural probiotic foods is yogurt, although yogurts filled with sweeteners and flavors usually do not contain the same amounts of good bacteria as completely plain yogurt made from regular milk and goat's milk.
Men's Fitness also provides a list of probiotic foods. The list is specifically targeted at men but contains many of the same foods as the aforementioned lists.