There is still much to learn about gut flora and the countless microorganisms that live naturally in our digestive tract. Generally, it's believed that these friendly bacteria block disease-causing germs from seeping into the bloodstream, they break down cancer-causing agents, they produce acids that kill harmful bacteria, they make Vitamin K and B and they help us digest fiber and lactose.

Sometimes our system has an imbalance where bad bacteria outnumber the good. Antibiotics are notorious for accidentally clearing out some of the good bacteria along with the bad. Therefore, it’s recommended that we take probiotic supplements, either in food, powder or capsule format, to restore the good bacteria again. Here’s a rundown of the most common probiotic foods and probiotic products on the market.

Activa probiotic yogurt is one of the most widely accepted probiotic supplements. The idea of bacteria living inside dairy products has been around for years, so Americans aren’t so “creeped out” by it. You can eat one four-ounce yogurt containing bifidobacterium each day for a month for $20. This product claims to reduce gas and bloating, while restoring digestive regularity again. Dannon says that their research indicates the the average time for food to travel from one end of the GI tract to the other was reduced by 10-30 hours. The best probiotic food on the American market is Activa made by Dannon.

Kashi Vive Cereal is another one of the probiotic supplements you may try. For $27/month, you’ll get a daily dose of lactobacillus probiotic acidophilus. The cereal’s manufacturers promise “digestive balance and immunity.” Even though this is the first probiotic wellness cereal on the market, skeptics argue that there’s no demonstrated evidence that the probiotic acidophilus strain has these health benefits. The Kashi spokespeople argue that this probiotic survives digestion, which is why they chose to include it, even if survival doesn’t equate with end results.

Probiotic supplements like Culturelle ($20/month) are said to “help promote regularity” and “help reduce bowel and stomach discomfort.” Two studies looked at the lactobacillus gg strain in Finland and Poland. While there was no real evidence that it “promoted regularity,” it did prove to help prevent diarrhea in 70% of children taking antibiotics. However, the results weren’t as encouraging in adults. In 2001, the Mayo Clinic reported no difference between Culturelle Probiotic consuming adults and placebo-taking adults on antibiotics. In the end, probiotic supplements may work for you, or they may just be another convenient advertising ploy.