Not only are probiotics typically safe to take every day, but some health experts recommend doing just that, according to the University of Maryland Medical Center. You'll find these "friendly" bacteria in fermented foods such as yogurt and Korean kimchi, as well as in a variety of over-the-counter supplements. For caution's sake, however, speak with your doctor before starting a probiotic regimen.

Probiotics are usually safe and already live in your digestive tract, Harvard Medical School notes. However, the U.S. Food and Drug Administration does not test nutritional supplements for safety, so stick with a reputable brand and research all supplement ingredients. UMMC also reports that doses exceeding 1 million to 2 million organisms may cause gas, diarrhea and upset stomach. In addition, the school warns that people with compromised immune systems, such as those on immunosuppressant drugs, should consult their physician before taking probiotics.

Taking probiotics may help ease diarrhea, especially cases caused by antibiotics, according to Harvard Medical School. Probiotics may also promote a healthy vaginal environment, balancing internal flora to help manage yeast buildup and urinary tract infections. Scientists are still examining these uses, however, and probiotics are not a substitute for professional medical care.