Probiotics — “good bacteria” — are thought to boost the immune system and may help with gut troubles, including diarrhea. They also repopulate your gut with the good bugs after a bout with a stomach illness — and it’s possible they may even lower the risk of type 2 diabetes.

If you’re tempted to get your fill through probiotic supplements, you could be in for a disappointment. That's because relying a pill may not give you the full variety of healthy bacteria that food sources do.

Another issue with supplements is that the “good” bacteria may not survive the trip through your stomach to the important destination: your large intestine, aka colon.

Related: Take Good Care Of Your Colon

Also, there's no guarantee that the pill contains what the label says it does. Nor does it guarantee that the live bacteria are, in fact, still alive, says Robynne Chutkan, MD, an integrative gastroenterologist and author of “ The Microbiome Solution.”

A supplement from a reputable company may be helpful, but getting a variety of good bacteria to your gut is best done the old-fashion way — through food — says microbiologist Maria Marco, PhD, an associate professor at the University of California, Davis. That's because food helps support the survival of healthy bacteria as they move through the digestive tract, she explains.

Best probiotic foods

Want to add more probiotics to you dinner plate? Look to fermented or cultured foods, which teem with beneficial bacteria. Eating a variety gives you a healthy mix of microbes for your "microbiome," which Chutkan defines as "the collective name for the trillions of bacteria that live in the digestive tract."

Related: 5 Tasty Ways to Eat More Yogurt

Here are six foods that deliver.

  1. Yogurt. Microbiologist Marco and her colleagues at UC Davis found recently that dairy products like yogurt not only effectively support the survival of “good bacteria” in the intestinal tract but may also improve the bacteria's capacity to provide health benefits. All yogurts with live bacteria contain Lactobacillus bulgaricus and Streptococcus thermophiles but you can get even more strains in some yogurts. Elizabeth Somer, RD, author of “Age-Proof Your Body,” says, "Skip those that list less than five kinds of bacteria."
  2. Kefir. This fermented milk drink is made with yeast and lactic acid bacteria cultures. Dairy products are not required to list the types of bacteria on the label, but at the very least "live and active cultures" should be on the label of kefir. If drinking a cupful is more tartness than you can stomach, choose a fruit flavored kefir. (Check the ingredients list to be sure it contains little or no added sugar, advises Somer.) Another option is making a smoothie with kefir and delicious ripe fruit. "You can even add [kefir] to instant pudding mixes," says Somer.
  3. Buttermilk. Traditionally, buttermilk is the sour-tasting liquid that remains after the cream in milk is churned into butter. Today, the buttermilk you buy is low-fat milk that has been cultured with Lactococcus lactis or Lactobacillus bulgaricus.
  4. Sauerkraut. Chop or shred cabbage, add salt, store in a mason jar and let the bacteria on the surface of the cabbage leaves do their thing. In a few weeks you have got probiotic-rich sauerkraut (instructions courtesy of thekitchn.com). Don’t count on getting probiotics from most store-bought sauerkraut, though. Processing done in the United States to ensure the safety and palatability of sauerkraut, pickles and other pickled vegetables destroys the live microorganisms. When choosing the store-bought kinds, look in the refrigerated section of the health food store or grocery. Those are more likely to contain living, healthy microorganisms.
  5. Kimchee. Kimchee is the Korean version of sauerkraut. It's made with Napa cabbage and other ingredients, such as scallions, red pepper, garlic ginger, daikon radish and fish sauce. For a recipe visit chow.com.
  6. Tempeh. This is fermented soybeans that have been placed in a mold to form a rectangular shape. Tempeh can be sliced and diced and added to almost any dish. It has more protein than tofu, so it's an especially good meat replacement. Since tempeh is kept refrigerated, the live bacteria created during the fermentation process are alive and well when you eat them. (Fermented soy products such as miso, natto, and some soy sauces also contain some healthy bacteria, though not nearly as much.)

Kombucha is another possible source of probiotics, but watch out. When this tea, fermented with sugar, yeast and bacteria to make a fizzy drink, is pasteurized for safety reasons, the healthy bacteria are destroyed. Unpasteurized kombucha is available, but there are reports that drinking it may cause stomach upset and other problems if it has been contaminated during processing.

Related: Kombucha, Kefir and Other Fermented Drinks: Bottoms Up?

You can ensure that the bacteria in kombucha are alive and well by making it yourself. But you must be meticulous and brew it in sanitary conditions. Since there is a risk of contamination, home made or unpasteurized kombucha is not safe for pregnant women or people with a compromised immune system. The Centers for Disease Control and Prevention advises anyone with a health condition to consume no more than 4 ounces of kombucha a day.

Give those "good" bugs something to eat

"Bacteria have a short lifespan, so it's important to feed them the right food so that they can multiply in the gut," says Chutkan, who is also founder of The Digestive Center for Women, in Chevy Chase, Maryland. The right foods or "probiotics," she explains, are those with soluble fiber. Good ones include asparagus, bananas, garlic, leeks, onions, green peas, lentils and white beans.

Related: Why Am I So Gassy?

Dianne Lange is a Lake Tahoe-based freelance writer specializing in health and travel. She is the author of four books on cancer and a former editor at SELF, Health, Natural Health and Prevention. Her work has appeared on websites such as RealAge.com, SymptomFind.com, WebMD and Everyday Health.