DEAR DR. BLONZ: I am considering buying a yogurt that emphasizes that it is made with special types of bacteria. Being old-school, I admit that the idea of bacteria in food being a good thing doesn't go down easy. Can you help explain this? And if I am unable to have this yogurt that often, should I take these bacteria as a dietary supplement? -- T.W., San Francisco, California
DEAR T.W.: Despite having a reputation for contributing to ill health, most are unaware that there is a vast colony of "friendly" bacteria living in the lower portion of our digestive system. Indeed, there are 10 times more of these bacteria in the colon than human cells in our bodies.
Referred to as our "intestinal flora," these microorganisms can be important to our general health. Scientists continue to learn about the extent of the flora's influence. While more or less stable, the flora can be affected by what you eat, the medications you take, and any of a number of stressors and lifestyle factors. Whenever the flora undergo a shift, there can be temporary discomforts such as cramps, diarrhea, bloating or gas.
The "diet" of the flora consists of the undigested food we eat. This helps explain why their makeup can be affected anytime we make big changes in our diet, such as the addition or removal of substances that are not efficiently digested, such as fiber. Digestive upsets can be minimized when dietary changes are gradual.
Physical or emotional stress can change our ability to digest the foods we eat, and this, in turn, can change what makes it down to the lower intestines where the flora live. Some researchers speculate that stress and shifting eating times might impact the flora and predispose the body to the discomfort and diarrhea often experienced by travelers and shift workers.
Nothing, however, affects the flora more than antibiotics. When taken to eliminate an illness-causing bacteria, antibiotics destroy friend and foe alike. This permits yeast organisms, normally kept in check by the friendly flora, to grow in greater numbers. That's one reason why those prone to yeast infections often experience flare-ups during and after taking a course of antibiotics.
Foods such as yogurt can contain the "probiotic" bacteria that can help strengthen the friendly flora. That means that one way to maintain healthy flora is to keep sources of friendly bacteria, like yogurt, acidophilus milk, or a flora-containing supplement in your diet.
Yogurt is made from milk that is usually cultured with two different bacteria: Streptococcus thermophilus and Lactobacillus bulgaricus. It tends to be tolerated by people who have lactose intolerance, because the yogurt bacteria produce their own lactose-digesting enzyme. Some refrigerated yogurts and many brands of frozen yogurt also contain added acidophilus and bifidus bacteria. These two types have special value because they can establish themselves as long-term residents in the intestinal flora.
Probiotic food supplements can be a convenient way to supply flora. Keep in mind that an effective supplement requires more than the mere presence of a "healthful" strain of beneficial bacteria; there has to be enough of it to make it through the human digestive system in sufficient numbers to have an impact. I encourage you to read more on the topic. A good start is this article on probiotics from the National Institutes of Health: tinyurl.com/hv5clnx.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.