Feed your 'good' bacteria
There's a lot more going on in your gut than just digestion, absorption and excretion. Trillions of microorganisms inhabit your intestines. In fact, there are 10 times more bacterial cells than human cells in your whole body. And these little beneficial bugs are busy! Scientists are beginning to unravel how friendly bacteria can protect your health and how the foods you eat can nourish them.
Fiber-rich plant foods give bacteria a fighting chance. Fiber feeds the healthy, hungry microbes, so that's one of many reasons you should have lots of high-fiber plant foods, including grains, legumes, fruits and vegetables, on your plate.
Medications, hygiene, age, health status, and diet can influence your microbe balance. Eating wisely is likely your best strategy for boosting the beneficial bugs. We see hints of the effects of food on intestinal bacteria when we examine diets around the globe.
In populations that consume a largely plant-based, fiber-rich diet, such as those in Africa and Asia, the predominant microbes are the beneficial ones, such as bifidobacteria and lactic acid bacteria, commonly known as probiotic bacteria. These crowd out the bad guys.
Fermented foods provide healthy bacteria. Eating fermented foods which contain live cultures can add healthy microbes to your intestines, explained Jeannie Gazzaniga-Moloo, PhD, RD, spokesperson for the Academy of Nutrition and Dietetics. Some of the foods you eat directly increase the quantity of healthy bacteria in your gut.
Many cultures throughout the world eat fermented foods. For example, sauerkraut is fermented cabbage common in German cuisine, and kimchi is a spicy version of fermented cabbage eaten in Korea. Fermented corn and millet are common in parts of Africa, and the Japanese use miso, a thick paste made from fermented soybeans. The most common fermented food in the U.S. is yogurt.
Read labels carefully when adding fermented foods to your diet, cautions Gazzaniga-Moloo. Some, but not all, contain live cultures.
"For example, sourdough bread is baked and fermented and meats are often smoked or cooked, rendering the once live cultures in the food product inactive. Filtering fermented beverages such as wine or beer effectively removes live cultures," she explained. When buying fermented foods, look for the word "live" such as "live cultured" pickles, sauerkraut or yogurt. If you're unsure, call the manufacturer to ask if the product has live cultures or if the food was processed in a way that kills or removes any beneficial bacteria." Heating or washing with chlorine will kill the good microbes, she adds.
Consuming probiotics-- live "friendly bacteria and yeasts" that are added to foods or taken as a supplement -- is another way to bolster your gut's population of healthy microbes. For probiotics to work, however, there must be a sufficient number of live bacteria present, and they must survive the hostile environment of the stomach, including its acidity, and reach the large intestine. The presence of the prebiotics, which act as food to nourish friendly bacteria in the large intestine, will ensure their growth and colonization.
Friendly bacteria unlock powerful nutrients. Unlike people, bacteria have the digestive enzymes needed to break down fiber for energy. In the process, the helpful bacteria produce gases and various acids that benefit the intestine and other body systems. The acids reduce the pH of the colon, making the environment less suitable for the pathogenic bacteria.
One of the acid byproducts, butyric acid, may help prevent colon cancer by feeding the cells that line the colon and helping them to grow into healthy cells, explained Rao. And another acid turns off a key enzyme in cholesterol synthesis, thus lowering blood cholesterol and decreasing the risk of cardiovascular disease. Better glucose control may be another benefit.
Bacteria in the gut also release trapped phytochemicals -- health-protective compounds in plants -- that otherwise would be unavailable to affect disease pathways. For example, the phytochemicals may be bound to fiber, or require metabolism by the bacteria to convert to an active compound. Compounds in broccoli, cabbage and other cruciferous vegetables, for instance, seem to have anti-inflammatory effects and decrease the risk of several cancers.
These vegetables contain glucosinolates which must be activated into the biologically active form called isothiocyanates either by chewing the raw vegetable, or if cooked, through the action of the intestinal bacteria, explained Johanna W. Lampe, PhD, RD, a nutrition scientist and associate division director, Public Health Sciences Division at the Fred Hutchinson Cancer Research Center, Seattle, Wash.
Isoflavones in soy may also exert anti-cancer effects. They're mostly in an inactive form when they enter the colon, but the gut bacteria convert them to an active form.
"Then the bacteria can also metabolize the isoflavone to additional bioactive compounds that we would never be exposed to if it weren't for our bacteria," adds Lampe. The interaction of the intestinal bacteria and the human body is anything but simple. Scientists have much more to learn.
Some studies suggest that exposure to soy foods in childhood may offer cancer protection in adulthood. One theory that requires additional research is that interactions between the intestinal microbes and isoflavones in the developing gut could affect development of the immune system and the long-term microbiotic environment of the individual.
Commit to diet changes
Changing the makeup of your intestinal bacteria requires long-term commitment, said Rao. It takes about three to six months of eating the right foods, such as high-fiber plant foods and fermented foods to see a difference. Even then, the composition will return to its previous profile if the diet is not maintained.
How can you tell if you've got an ideal composition of microbes in your gut? One hint is to look at your feces.
"We can characterize people into either floaters or sinkers, depending on how their fecal material behaves," he said. Feces that float suggest healthy fermentation in which a lot of carbon dioxide gas is produced and trapped into the fecal matter. Sinkers represent poor fermentation with little trapped carbon dioxide and poorer health consequences, he explained.