Americans spend millions of dollars on anti-bacterial soap, sponges, moisturizers, disinfectants and a whole array of cleaning products to kill germs, yet microbes -- far from being public enemy number one -- actually provide essential health benefits. The concept that tiny organisms, such as bacteria and fungi, can have health benefits is not new. For thousands of years, people have benefited from foods, such as yogurt and cheese, that are rich with microorganisms. Only recently however, has modern nutrition come to understand the health benefits of certain microorganisms when added to foods or taken as dietary supplements.

The human intestinal tract is a complex ecosystem of microbes, many of which live in harmony with their human hosts and do not promote disease or illness. Microbes that are health-enhancing are called "probiotics." Probiotics maintain the health of the cells lining the small and large intestine, which boosts the digestive tract's ability to absorb nutrients and fight unwanted toxins. Medical researchers are now looking into the various uses of probiotics to prevent and treat gastrointestinal disorders such as antibiotic-induced diarrhea, irritable bowel syndrome, "traveler's diarrhea," and other bacterial and viral infections. A recent issue of the Journal of the American Medical Association highlighted information from the World Congress on Pediatric Gastroenterology, Hepatology and Nutrition on the use of probiotics to improve health and fight disease.

Lactobacillus acidophilus (L. acidophilus) is a probiotic that has been well studied by scientists. L. acidophilus lives in the intestines and vagina and prevents bacterial disease, partly through the production of lactic acid. It also produces lactase, the enzyme that breaks down milk sugar (lactose) into simple sugars. People with lactose intolerance may benefit from the lactase produced by the microbes.

The primary dietary sources of L. acidophilus include the following:

• Acidophilus milk
• Yogurt (with live L. acidophilus)
• Miso
• Tempeh
• Fermented dairy products
• L. acidophilus is also available in freeze-dried granules, powders, capsules, and liquid form.

To be health-enhancing, orally ingested probiotics must endure a tough ordeal -- they have to survive the digestive process, implant in the gut, and multiply. Unfortunately, most yogurts and fermented milks contain a strain of probiotics that are lucky to make it out of the digestive process alive. If they do survive, their effects are rarely long lasting. This is why the most effective probiotics are taken as dietary supplements, such as lactic acid bacteria bifidobacterium sp. and lactobacillus sp.

Part of the mutual benefit between microbes and humans is the ability of the lactobacilli in the colon to break down carbohydrates, such as insulin and fructoliogsaccharide (FOS) to short-chain fatty acids, which provides fuel for the cells in the colon. Carbohydrates like FOS are called prebiotics and serve as food for the "friendly bacteria." Sources of prebiotics include onions, bananas, tomatoes, honey, barley, garlic and wheat.

Prebiotics should be taken along with the probiotics, as food or in a capsule form. It is important to note however, that adverse interactions between medications and some supplements are common. For example vitamins and minerals that exceed recommended dietary allowances may be harmful. Some common foods, including nuts, dairy products, fish, and eggs, may trigger allergic reactions, which may require emergency medical care. If you are considering taking dietary supplements or dramatically changing your diet, it is important to first consult with your healthcare provider or nutritionist.

For more information on nutrition, including a helpful a rating guide to nutrition sites on the Internet, contact the Tufts University Nutrition Navigator at www.navigator.tufts.edu. Another helpful source is the American Dietetic Association in Chicago, Illinois at 800-877-1600 or visit them on the web at www.eatright.org.

Reference

Friedrich MJ. A bit of culture for children: probiotics may improve health and fight disease. JAMA. 2000;284(11):1365-1366.