Prebiotics and Probiotics: The Bacterial Good Guys

Meet the bacteria that keep your digestive system humming.

Most of us do whatever it takes to banish bacteria from our homes. We scrub kitchen and bathroom surfaces with products containing bleach. We wash fruit and vegetables in plain water or use a specialized antibacterial produce wash. Our dishwashers scrub away all traces of grime, and we thoroughly wash our hands before we prepare food and eat.

Scientists estimate there are more bacteria in or on the human body (about 100 trillion bacterial cells)—representing 400 different types of bacteria—than there are human cells in it (about 10 trillion). Mary Ellen Sanders, PhD, an internationally known expert on probiotics, notes that laid end to end, the bacteria on our bodies would circle the Earth 2.5 times. Who knew?

Most of us don’t realize it, but not all the bacteria in our bodies are harmful. In fact, some actually help our bodies stay healthy.

Bacteria Wearing White Hats — The Good Guys

Bacteria in the gastrointestinal tract can be harmful, neutral, or helpful. In the large intestine, helpful bacteria complete the digestion process on any undigested food components, such as lactose in lactose-intolerant people, or fibers resistant to the enzymes in the small intestine. And some bacteria actually produce vitamin K, a fat-soluble vitamin important in blood clotting.

According to the International Scientific Association for Probiotics and Prebiotics, probiotics are live microscopic-sized organisms that can provide health benefits when consumed in adequate amounts, and prebiotics are nondigestible substances that help probiotics grow and thrive. In an optimal environment—for example, in your gastrointestinal tract—probiotics and prebiotics work together synergistically to play a role in maintaining your overall health.

Benefits of Probiotics

Not all probiotics are alike, and the health benefits are strain specific; each individual species and strain provides different health benefits.

The FDA requires that Streptococcus thermophilus and Lactobacillus bulgaricus are used to make yogurt. These two probiotics help decrease lactose intolerance and have been shown to prevent diarrhea caused by rotovirus, often common in children’s day care settings. But unless your yogurt label says it contains live and active cultures, you won’t get these benefits.

Lactobacillus rhamnosus GG (LGG) and Saccharomyces boulardii may be helpful in treating antiobiotic-associated diarrhea. Antibiotics are designed to destroy harmful bacteria but also kill off helpful bacteria, which can result in diarrhea. A study published in the Journal of Pediatrics in 2001 demonstrated that only 3% of hospitalized patients developed diarrhea when they used a supplement containing LGG, as opposed to 33% of the patients who received a placebo.

Lactobacillus acidophilus has been shown to help balance the vaginal pH level, reducing a woman’s risk of developing yeast infections. This particular strain of probiotics produces hydrogen peroxide, which creates an inhospitable environment for yeast. Think of using L. acidophilus as a sort of weed killer to prevent yeast infections from developing and you get the picture.

The Bifidobacterium lactis strain of probiotics is predominant in the gut of breast-fed infants and is believed to be at least partly responsible for their enhanced immune systems. One study among older adults showed that supplementing their diets with B. lactis enhanced their immune systems as well. There’s also research into possible cancer-preventive effects of some strains of probiotics. The only human study looked at using Lactobacillus casei fermented milk to prevent recurrence of superficial bladder cancer; the people who drank this milk were cancer free for almost twice as long as were those in the group that didn’t receive probiotics. More research is needed, but scientists are hopeful that probiotics may prove to be an effective tool in fighting cancer.

Lactobacillus reuteri protectis given to workers at Tetra Pak in Sweden decreased the frequency of sick days.Twenty-six percent of the workers who received a placebo reported sick for work, as opposed to only 11% who received the probiotics. Among the 53 shift workers in the study, 33% in the placebo group reported sick compared with none in the probiotic group.

There has been considerable research into the role of probiotics in treating the symptoms associated with irritable bowel syndrome and inflammatory bowel disease (gas, bloating, stomach cramps, and diarrhea). In one study of 362 people with irritable bowel syndrome, 62% of those who used Bifidobacterium infantis 108 reported a decrease in symptoms vs. 42% who received a placebo.

Role of Prebiotics in Health

According to Wendy Reinhardt Kapsak, MS, RD, director of health and nutrition at the International Food Information Council, prebiotics are basically food for probiotics. Whole grains, onions, bananas, garlic, honey, leeks, artichokes—foods that contain fiber—are natural sources of prebiotics. Prebiotics can also be isolated from chicory or synthesized from sucrose and added to foods. Inulin and fructo-oligosaccharides are two of the most common prebiotics added to foods. Reinhardt Kapsak notes that anyone who eats a healthy diet containing plenty of fruits, vegetables, and whole grains gets plenty of prebiotics.

What About Safety?

Prebiotics and probiotics are considered safe for anyone who is generally healthy. If your immune system is compromised—for example, if you have cancer and are undergoing chemotherapy or radiation treatment, or you have another disease that affects your immune system—check with your physician before using any product containing probiotics. It’s possible that instead of providing health benefits, probiotics may instead do harm to someone with an impaired immune system.

Getting Your Daily Dose of Probiotics
There are three sources of probiotics that you can consume on a regular basis:

1. In dairy or soy milk products that have been inoculated with probiotic cultures.

2. Added to milk-based products that are fermented and contain high levels of probiotics.

3. In a dried and concentrated powder, capsule, or tablet.

Dairy products are often the probiotic carrier of choice because milk buffers stomach acid, protecting delicate probiotics until they reach the friendlier climate in the intestines and because refrigeration helps keep probiotics alive and stable. Plus, we’re used to seeing the “contains live and active cultures” label on dairy products. It’s not as appetizing to think about a sirloin steak containing live and active cultures, is it?

The National Yogurt Association established a Live & Active Culture seal to identify yogurt products that contain live, active cultures. Yogurt that contains at least 1 trillion live lactic acid bacteria per gram and frozen yogurt containing at least 100 million live lactic acid bacteria per gram can use the seal. However, the seal doesn’t differentiate between strains of bacteria, leaving consumers in the dark about specific health benefits.
Food companies have jumped on the probiotic bandwagon, developing new products with higher levels of specific probiotic strains and marketing them to fit a health niche. The scientific research, however, produces contradictory results.

Dannon makes DanActive, which contains 100 trillion live L. casei per serving. Dannon claims that DanActive helps strengthen the body’s immune system, but an Italian study using this product was inconclusive. Dannon has a trademark for this particular probiotic that it calls L. casei Immunitas.

Dannon also makes Activia yogurt, containing Bifidobacterium animalis to help decrease gas and bloating. Dannon’s research shows that its yogurt decreases the time it takes food to travel through the gastrointestinal tract, which can decrease gas and bloating. Dannon also trademarked this probiotic, naming it Bifidum regularis.

Stonyfield Farms uses general yogurt starter culture bacteria, S. thermophilus and L. bulgaricus, along with L. acidophilus, Bifidus, L. casei, and L. rhamnosus. Remember the L. reuteri used in the Swedish workers to decrease sick days? Stonyfield Farms uses the same strain.

Knowledge = Power = Health

Since the particular strain of probiotics isn’t necessarily identified on food labels, consumers will need to contact companies to learn this important information. Ask about specific probiotic strains present in their foods, along with any research that proves the health benefit of these individual strains. It’s also important to ask about the amount of probiotic proven to be beneficial in the studies, since it can differ among different strains and even for different uses.

Reinhardt Kapsak emphasizes that prebiotics and probiotics boost health from the inside out, creating a healthy environment in the digestive tract that she likens to a beautiful garden. If you’re looking for general health, enjoy fruits, vegetables, and whole grains to increase prebiotics while at the same time choose one to two servings of dairy products that contain probiotics each day. But if you’re looking for a specific health benefit from probiotics, perhaps to reduce diarrhea or symptoms of irritable bowel syndrome, check with your physician and registered dietitian for specific guidance on which product to use.

— Lynn Grieger, RD, CDE, cPT