There are two ways to get more good bacteria into your gut: fermented foods and dietary supplements. Fermented foods are the best source, as probiotic supplements, which are typically sold over the counter, are reserved to treat specific ailments as suggested by your doctor, and not recommended for everyday use. Plus, supplements do not have the same FDA oversight as medications do.
So, a big question remains: How many probiotic foods do you need? That's not easy to answer.
There is no recommended daily intake for probiotics, so there is no way to know exactly which fermented foods or what quantity is best. Therefore, the general guideline is to just add as many fermented foods to your daily diet as possible.
Why fermented foods? Fermenting is one of the oldest techniques for food preservation. Mankind has been fermenting foods and drinks like beer and wine for centuries. Foods that are fermented go through a process of lactofermentation in which natural bacteria feed on the sugar and starch in the food, creating lactic acid. This process creates an environment that preserves the food and promotes beneficial enzymes, B vitamins, and omega-3 fatty acids, as well as various species of good bacteria.
Another way to look at fermentation is that it takes one type of food and transforms it into another kind. For instance, cabbage becomes sauerkraut, cucumbers become pickles, soybeans turn into miso, and milk can be made into yogurt, cheeses, and sour cream.
Not all fermented foods contain probiotics. Some foods undergo steps that remove the probiotics, as with beer or wine, or make them inactive, like baking and canning. However, most fermented foods are probiotic foods as well.
If there is a potential downside to fermented foods, it is that their taste and smell can be quite strong, which may be unpleasant for some people. The unique flavors and textures of fermented foods are due in part to the different species of bacteria used.
On the upside, there are many types of fermented foods from which to choose, so there is a good chance you can find something you will enjoy.
The most common fermented foods that naturally contain probiotics, or have probiotics added to them, include yogurt, kefir, kombucha, sauerkraut, pickles, miso, tempeh, kimchi, sourdough bread and some cheeses.
Yogurt is considered the most valuable player of probiotic foods because it has a flavor and texture that's generally appealing to Western palates. The number and type of bacteria species can vary depending on the yogurt brand. The probiotic content of yogurt products can range from 90 billion to 500 billion CFU per serving. (CFU stands for colony- forming units, which is how many bacteria are able to divide and form colonies.) Look for the words "live and active cultures" on the label.
How to use: Yogurt is easy to add to your diet. Besides having it for breakfast or a midday snack, you can substitute yogurt whenever you use mayonnaise in egg salad or potato salad, or in almost any baking recipe. Yogurt also can be the basis for sauces, salad dressings, or marinades.
To learn more about other foods containing probiotics as well as the role of probiotics in your overall health, read The Benefits of Probiotics from Harvard Medical School.