The human intestine is inhabited by billions of bacteria. Most are good, or “beneficial bacteria.” Good bacteria live in your intestine and consume the food you eat. They actually do most of your digestion for you. You want a diverse variety of beneficial gut bacteria. The collection of bacteria inside a person's intestine is called the “human microbiome.” A diverse microbiome is absolutely necessary for a you to have healthy digestion and an overall healthy life. Research in this area is new, but current studies suggest that people need to eat a healthy mix of good bacteria to thrive. We call foods that contain a healthy mix of bacteria “probiotic.”
Your traditional cultural foods may already have the bacteria you need.
Virtually all traditional diets include foods that contain healthy beneficial bacteria. Most are pickled or fermented foods. Fresh fruits and vegetables have bacteria on them from the soil in which they grow. Traditional cooks make pickles by putting fresh vegetables in salty water, called brine. As the vegetables pickle, the good bacteria on them grows, while most bad bacteria die off. The good bacteria make lactic or acetic acid, which tastes sour -- like a pickle. This method is how cooks make olives, kimchi, sauerkraut, pickled turnips, and other traditional foods. These foods are probiotic.
Breads and yogurts can also contain beneficial bacteria. For example, sourdough contains good bacteria. A bit of dough containing the living bacteria is kept from past sourdough batches, and added as a starter to grow more bacteria for each new batch of dough.
The traditional market vs. the modern American supermarket.
Foods containing beneficial bacteria are fragrant, even smelly. Imagine walking into a traditional Italian grocery store. You are surrounded by barrels of tangy olives, sour pickled peppers, sweet pickled tomatoes. Peppery hams, spicy salamis, and pungent cheeses hang from the ceiling. Each of these traditional foods contains its own unique blend of healthy bacteria. The bacteria produce volatile organic esters; we smell them as complex delicious odors. Their living bacteria can help keep us healthy. Probiotic foods are alive.
In contrast, the modern American supermarket is designed to be clean, odor free, and house shelf stable foods. The processing to make food sealed-up and odor-free kills all the bacteria, both good and bad. Pickles or olives that have been boiled, so they can sit for years in jars or cans, are sterile. These foods are dead.
Just a little is enough.
The key to getting healthy probiotics is not quantity, but variety. For example, traditional Korean cooks make dozens of types of kimchi by fermenting many kinds of vegetables with herbs and spices. Typical Korean meals include small amounts of several kinds of kimchi at a single meal. You don't need to eat huge quantities of fermented foods. A pickle and some olives with lunch is enough. A little fresh sauerkraut on your hot dog is enough.
Where to get your probiotics, food or supplements.
Some health and specialty markets have real probiotic fermented foods available. If you can find them, begin to add them to your meals. If not, you can buy refrigerated probiotics at health food stores. Take probiotic supplements at the beginning of your meal. Just as with food, variety is the key. Buy a brand that has different kinds of bacteria— a large quantity is not necessary. If you can't decide which brand to buy, rotate among a few different kinds. Don't consistently take the same brand because you want as much variety as you can get.
Finally, eat your vegetables! The bacteria in your intestine, your personal “human microbiome” wants to eat vegetables. Feed your bacteria by eating a variety of fresh, high fiber vegetables. Eating fruits and vegetables is important for healthy intestinal function and regular bowel movements. For a healthy life, eat lots of vegetables and some probiotic foods every day.