Can probiotics change birth control effectiveness?

Dear Don't Want a Grumbly AND Pregnant Tummy,

Now, before we get into the answer in more depth, here's what you want to know: Neither probiotics nor prebiotics have been shown to affect the effectiveness of birth control pills. Like antibiotics, probiotics do not affect hormone levels in the body, so your birth control should work just as well as it normally does (assuming consistent and correct use). Feel free to eat all the yogurt and miso soup you crave, or swallow those acidophilus tablets when you like — they will not affect that other little pill you take each day.

It is understandable that after a ten year track record of successful birth control use you would want to keep your tummy grumble- and baby-free. Before answering your question, a brief correction that may come as a happy surprise to you: In the vast majority of cases, antibiotics have not been shown to decrease effectiveness of the birth control pill. There is one exception — the antibiotic rifampin — but rifampin is used mainly to treat tuberculosis and is rarely prescribed in the United States. So, while taking antibiotics will hopefully kill whatever bacteria is making you sick, it doesn't have to kill your sex life. 

That correction out of the way, let's move onto the topic of pro- and prebiotics. Probiotics are live microorganisms often referred to as "friendly" or "good" bacteria. Probiotics are quite similar to the healthy bacteria naturally occurring in the human gut. Some people may wonder, um, why exactly would anyone ingest live microorganisms? People take them for a variety of reasons. Many take them following or during a course of antibiotics, to replenish the stock of friendly bacteria in the intestines that antibiotics tend to kill.

Probiotics are also used to:

• Ease the symptoms of lactose intolerance
• Boost the immune system
• Increase energy
• Treat diarrhea
• Prevent and treat urinary tract infections
• Treat irritable bowel syndrome

People take probiotics in the form of tablets, capsules, or powders (available at pretty much any health food store), while others consume them by eating plenty of fermented foods like yogurt, miso, tempeh, and kombucha (fermented tea), all high in probiotic content. Probiotics are considered safe, as there have been very few reports linking them to any adverse reactions. However, those with badly damaged GI tracts or at risk for opportunistic infections should consult a health care professional before starting to use them. Prebiotics are un-digestible components of food that stimulate the growth and/or activity of beneficial microorganisms that are already in the colon — a support system for probiotics, if you will.