Saturday, July 13, 2024
Dr. Louise

What's the difference between prebiotics and probiotics


Last month, Maria was diagnosed with a bladder infection, and the urgent care physician prescribed an antibiotic. Unfortunately, that didn't fix her burning and urgency, so a second, more powerful antibiotic was prescribed. That cured her but triggered a different problem: cramping and intermittent diarrhea. She came to me for help. “I can’t go shopping without making several urgent trips to the nearest bathroom.” 

I suggested she start taking a probiotic, and she called back a week later to report that her bowels were finally returning to normal.

Probiotics are friendly bacteria, yeast, and parasites that live in our intestines and vagina. More than 400 separate strains of these organisms are vital in helping us break down our food and absorb its nutrients into our bodies. 

Probiotics have another important job: discouraging the growth of “bad” bacteria and other organisms that can make us sick. They do this by competing with them for the critical nutrients they need. Some probiotics produce lactic acid and other compounds that discourage the growth of other organisms and keep your intestines in balance.

Taking powerful antibiotics killed off the bacteria in Maria’s bladder, relieving her from her urinary urgency and burning. But while doing that, those medications also killed off her “good” intestinal bacteria, leaving room for the “bad” bacteria to take over. This caused her to have diarrhea, called antibiotic-associated diarrhea. Luckily, taking probiotics can decrease the risk of diarrhea by up to 70%. 

The three most common probiotics that help keep our intestines in balance are Lactobacillus, Bifidobacteria, and the fungus Saccharomyces. Some probiotics work by secreting antibacterial compounds like hydrogen peroxide, lactic acid, and acetic acid. 

Lactobacillus makes lactic acid, which increases the acidity of vaginal tissue. This helps protect you from both bacterial and yeast vaginal infections. The bacteria Gardnerella is an organism that usually lives in your vagina. 

An antibiotic can disrupt that balance and allow overgrowth of certain bacteria, causing inflammation and an infection called bacterial vaginosis. Lactobacillus bacteria secrete hydrogen peroxide inside the vagina, which is deadly to Gardnerella and helps keep it under control. 

The helpful fungus Saccharomyces, available without a prescription as Florastor®, has been shown to help prevent antibiotic-associated diarrhea. There is also evidence that combining Lactobacillus and Bifidobacteria bacteria when treating antibiotic-associated diarrhea is more effective than either organism alone.

Some strains of Lactobacillus are better than others at attaching to the lining of your intestine. Other strains are best for re-establishing themselves when the “bad” bacteria are already in place. One of the best at adhering to your gut lining is Lactobacillus GG, available over the counter as Culturelle®.

There is a lot of interest in using prebiotics as well as probiotics to help your intestines and vaginal tissue stay healthy. Prebiotics differ from probiotics because probiotics are actually living organisms, while prebiotics are carbohydrates. 

Prebiotics work as support staff to your probiotics, feeding them and encouraging their growth by the way they change your intestinal environment. Prebiotics work like “Miracle Grow®” to establish and support ideal conditions for beneficial bacteria and fungi growth. Prebiotics are less expensive than probiotics because they don’t have to be protected from excess heat and preservatives. 

Dr. Louise Achey, Doctor of Pharmacy, is a 44-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog,

©2024 Louise Achey


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