Probiotics and Prebiotics

Sources of Probiotics

Food
Fermented foods are made through the growth and metabolic activity of a variety of live microbial cultures. Many of these foods are rich sources of live and potentially beneficial microbes. Some fermented foods, such as sourdough bread and most commercial pickles, are processed after they are fermented and do not contain live cultures in the form in which they are consumed. Many commercial yogurts, another type of fermented food, contain probiotic microorganisms, such as Lactobacillus bulgaricus and Streptococcus thermophilus.

The live microorganisms used to make many fermented foods, including yogurt, typically survive well in the product throughout its shelf life. However, they usually do not survive transit through the stomach and might not resist degradation in the small intestine by hydrolytic enzymes and bile salts and, therefore, might not reach the distal gut. However, legitimate probiotic strains contained in yogurt or other foods do survive intestinal transit.

Fermented foods that contain live cultures but do not typically contain proven probiotic microorganisms include many cheeses, kimchi (a Korean fermented cabbage dish), kombucha (a fermented tea), sauerkraut (fermented cabbage), miso (a fermented soybean-based paste), pickles, and raw unfiltered apple cider vinegar made from fermented apple sugars.

Certain unfermented foods, such as milks, juices, smoothies, cereals, nutrition bars, and infant and toddler formulas, have added microorganisms. Whether these foods are truly probiotics depends on the microorganism levels they contain when they are eaten, whether they survive intestinal transit, and whether their specific species and strains have health effects.