Nutrition Connection: "Good" Germs in Food • Winter 2007
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Bacteria aren’t all bad. Even though the most harmful bacteria, such as E. coli, Staphylococcus, and Salmonella capture headlines, there are many beneficial bacteria in action behind the scenes. Today, health scientists are looking closely at what good bacteria can do.
If you have studied nutrition, you may already know that bacteria in the intestinal tract produce some of the vitamins we need every day. In the human intestinal tract, about 500 types of bacteria may exist at any one time, and not to be ignored—they number 100 trillion!
They thrive in mini-populations or “colonies,” and each is influenced by environmental conditions that favor or hinder growth. These populations actually compete with each other for survival, each trying to dominate in the intestinal tract.
Increasing research on the benefits of breast milk for infants points to a long-chain form of galactose (carbohydrate) naturally present in the milk, which favors growth of a species called Bifidobacteria. In turn, these bacteria protect against rotavirus infection, one of the most prevalent and serious causes of diarrhea in young children.
This is just one example. Bifidobacteria, Lactobacillus, and others are turning up as major players in preventive health. They’ve taken on the name probiotics, meaning “for life,” or compounds that promote health. The United Nations Food and Agricultural Organization and the World Health Organization define “probiotics” as live microorganisms, which, when administered in adequate amounts, confer a health benefit.
Some of the interest in probiotics was triggered just 18 years ago by a suggestion from a Nobel-prize winning scientist, Elie Metchnikoff, who hypothesized that Bulgarian peasants lead very long lives due, in part, to fermented milk products in their diets.
Food for Germs
A big factor influencing which bacteria thrive in our intestines is the food we provide them. (Remember, bacteria have to eat, too!) Many forms of carbohydrate, especially indigestible carbohydrate or “fiber,” are prized by health-promoting microbes. For example, inulin, classified as a soluble dietary fiber with about 1.5 calories per gram, is popular food for probiotic bacteria.
Inulin occurs in plant foods such as onions and asparagus, and is also used as a food additive, where it serves as a fat replacer or bulking agent. Inulin is used in cheese, baked goods, icings, whipped cream, fillings, and even processed meats.
Inulin is an example of a prebiotic, which means a carbohydrate that nurtures the growth of specific probiotic bacteria in the colon. In other words, a prebiotic (carbohydrate) is anything that serves as food for probiotics (bacteria).
Even without intake of live bacterial cultures, simply consuming prebiotic carbohydrates such as inulin can promote growth of “good” germs in the intestines.
Some of the benefits believed to come with flourishing populations of “good germs” in the intestinal tract include:
Cancer prevention. Probiotics seem to inactivate certain cancer-causing substances in the intestines, probably helping to prevent cancer in the colon, as well as in other parts of the body. In addition to their direct effects, probiotics have their own metabolism, producing compounds such as short-chain fatty acids that may also help prevent cancer.
Treatment for irritable bowel syndrome. Research suggests regular consumption of probiotics may help keep this and other chronic intestinal conditions, such as Crohn’s disease and ulcerative colitis, under control.
Protection against intestinal illness due to aging. Older individuals are particularly susceptible to changes in bacterial populations due to changes in the intestinal tract (e.g., decreasing immunity in the intestinal mucosa and decreasing acid production). This means harmful bacteria can take over. Among some elderly individuals, diarrhea due to the bacteria Clostridium difficile can become problematic, and consuming foods high in probiotics seems to help.
Help for diarrhea resulting from antibiotics. At any age, a person taking antibiotics is also susceptible to changes in bacterial populations, because the medicine destroys many bacteria and upsets the healthy balance. Consuming live probiotic bacteria can prevent or minimize intestinal illness, according to research.
Urogenital health. Probiotic intake may help prevent yeast infections and urinary infections. Preliminary research indicates probiotics may help prevent kidney stones, too.
Healthy immune system. Researchers suggest that probiotics contribute to a healthy immune system, helping to prevent a range of illnesses. For example, one study shows that employees taking probiotics had fewer sick days over an 80-day period than those who did not.
Allergy. Adding probiotics to the diets of infants appears to offer protection against allergy, eczema, and asthma.
Weight gain. For children with AIDS, probiotics may promote weight gain.
While the research is exciting, the practical application has some provisos. Scientists caution that it may be important to match specific strains of beneficial bacteria to the case in order to achieve health benefits, and the advice isn’t all in as of yet.
Choosing a product
Generally, probiotics are available in fermented diary foods, such as yogurt with “live cultures,” and a yogurt-like beverage called kefir. Exact strains of bacteria range from one product to another.
Also, probiotics are available in pill forms as “supplements”. Some microbiologists encourage the choice of food over pills, warning that labeling requirements do not require a manufacturer to prove the bacterial content of their products. A consumer cannot be certain all products contain live cultures in effective amounts.
Probiotic-containing foods, such as yogurt and kefir, fall under “food” rather than “drug” regulations, so regulation is not as stringent as it could be, notes the American Academy of Microbiology, adding, “At present, the quality of probiotics available to consumers in food products around the world is unreliable, though some manufacturers have been better able to deliver high quality than others.” (see report under More Info below).
Scientists raise only very few safety concerns about probiotics. Occasionally, a probiotic can aggravate an illness. For example, despite the value of probiotics in Crohns diseases, there have been cases where probiotic intake has made Crohns symptoms worse rather than better.
American Academy of Microbiology Report. Probiotic Microbes: The Scientific Basis: www.usprobiotics.org/docs/AAM%20
Canfield, W. Your Health: Probiotics and Prebiotics. USDA: http://ars.usda.gov/News/docs.
Harvard Medical School. Health benefits of taking probiotics: http://www.health.harvard.edu/fhg/
US Probiotics: www.usprobiotics.org
A Healthy Balance
The upshot is that fostering a healthy balance of the trillions of bacteria in the intestines can support good health. There are two ways to reap the benefits:
- Consume plant foods high in dietary fiber, especially in prebiotics such as inulin. Food choices include onions, asparagus, and many others.
- Consume foods with live cultures of health-promoting bacteria, e.g., yogurt or kefir.
The “good germs” story is one of many examples of the sophistication of today’s nutrition science, proving that a healthful food is more than just a set of human nutrients. A dietary manager can safely incorporate yogurt and other fermented milk products into the diets of healthy clients.
By Sue Grossbauer