Friendly Bacteria

Probiotics are “good” bacteria and yeasts that live mainly in your digestive system. They help your intestines sustain a beneficial balance of microorganisms by reducing the growth of harmful bacteria.

“Probiotics are particularly helpful for maintaining normal bowel function and good digestive health,” says Bruce Eisendorf, M.D., a family medicine doctor at the Palo Alto Medical Foundation. “They also keep your immune system strong so you can fight and prevent infection.”

Some studies show that probiotics may also help prevent plaque, tooth decay, bad breath and gum disease by deterring the growth of infectious bacteria in your mouth.

Several factors can disrupt the delicate balance of your body’s “good” and “bad” bacteria, including:

• A diet that includes refined sugars and grains, processed food and hydrogenated fats and oils.
• Diarrhea, caused by antibiotics, viruses, bacteria or parasites.
• Infections, like vaginal yeast and urinary tract infections.
• Gastrointestinal conditions, such as inflammatory bowel disease, colitis and stomach flu.
• Certain medications, like antibiotics, aspirin, antacids, painkillers, laxatives ibuprofen, birth control pills and corticosteroids.

Probiotics live naturally in your body, so you don’t necessarily need probiotic foods or supplements to be healthy; but if your gut flora needs help, you can increase probiotics’ number by taking dietary supplements and eating cultured and fermented foods, such as kefir, yogurt, miso, tempeh, kimchi, sauerkraut and kombucha.

Probiotics and Prebiotics: Working Together

Probiotics work better when they don’t act alone. “To get the full health benefit of probiotics, prebiotics are part of the equation,” Dr. Eisendorf says.

Prebiotics are indigestible carbohydrates that feed probiotic bacteria and help them grow. They exist naturally in most whole grains and beans, especially oats, beans, bran, whole barley and whole-wheat products, as well as many fruits and vegetables, including most greens, garlic, bananas, artichokes, asparagus and chicory root. Even red wine offers some prebiotics.

The Future of Probiotics

Although probiotics research has exploded recently, some facts about their effectiveness remain unclear. For example, within the two main groups of probiotics—Bifidobacterium and Lactobacillus—doctors are still trying to pinpoint which strains are the most helpful and what’s the optimal amount to take.

If you’re a healthy adult, probiotic- and prebiotic-rich foods are safe to eat; but if you want to try a supplement, talk to your doctor first about brand, strain and dose, especially if you have a compromised immune system.