Feed Your Flora
Saturday, February 23, 2008 (18:35:31)

Posted by Cougar

Feed Your Flora

By Lisa Turner

Have a gut feeling that something’s not quite right in your intestinal world? You may benefit from a good dose of friendly bacteria. Maybe you’re familiar with probiotics, beneficial bacteria that live in the intestines. But you may not know about prebiotics, certain types of soluble fiber that help those beneficial bacteria multiply. Compelling studies show that prebiotics are equally as important as probiotics. “Without prebiotics, probiotics couldn’t live for long or do their job as well,” says Gary Huffnagle, PhD, professor of internal medicine and microbiology at the University of Michigan and author of The Probiotics Revolution (Bantam Dell, 2007). “At the most basic level, prebiotics promote the growth of probiotics in the body by providing nutrients they need to survive and multiply. And science is beginning to recognize that microbes that live within us are crucial to our health.”

Normally, a healthy gut teems with microbes, both “good” ones—like Lactobacillus acidophilus and L. bulgaricus—and “bad” ones, like pathogenic bacteria, viruses, and fungi. The harmful bacteria don’t cause trouble, so long as they’re kept in check by friendly flora. But when the beneficial bacteria are killed off—often by the use of antibiotics, stress, or a diet high in processed, refined foods—the harmful microbes thrive. That’s when problems arise, such as diarrhea, constipation, nausea, bloating, ulcers, and other gastrointestinal woes, as well as yeast infections, reduced immunity, and more serious illnesses, like colorectal cancer.

Probiotics like lactobacilli and bifidobacteria prevent these maladies in several ways: They make the intestines less habitable for harmful bacteria by changing the chemistry of the gut; they produce antimicrobial compounds that destroy pathogenic microbes; and they “crowd out” bad bacteria by competing with them for nutrients and for surface area along the walls of the intestines. Probiotics also appear to enhance our own immune function, says Mary Ellen Sanders, executive director of the International Scientific Association for Probiotics and Prebiotics. They do this, in part, by stimulating the production of infection-fighting white blood cells.

Food for flora
But like any living organism, probiotics need nourishment. That’s where prebiotics enter the picture. In the broadest terms, prebiotics are indigestible ingredients you eat that stimulate the growth of beneficial bacteria by serving as “food” for them. The most common prebiotics are inulin and fructo-oligosaccharides (FOS), types of soluble fiber similar to oat bran, psyllium, and pectin in apples. Prebiotics differ from these soluble fibers, however, in that they specifically encourage the growth of probiotics, especially bifidobacteria and lactobacilli, in the gut. Inulin and FOS also confer some of the same health benefits associated with other types of soluble fiber, such as providing bulk to move waste through the intestines and helping to sweep out potential carcinogens.

You can add prebiotics to your diet naturally by eating foods high in these soluble fibers. Inulin and FOS are found mainly in asparagus, artichokes, onions, bananas, garlic, leeks, and chicory in small amounts, says Glenn Gibson, PhD, professor in the Food Biosciences Department at the University of Reading, England. Some fortified foods, like fermented dairy drinks, yogurt, and Attune granola bars, have prebiotics added to them. All these promote healthy flora in the gut.

If you’re trying to treat a specific condition, however, you may want to go with prebiotic and probiotic supplements to ensure a higher and more accurate dose. Five to 8 grams a day (spaced throughout the day) is standard, says Gibson. Larger amounts can cause gastrointestinal discomfort, like bloating or flatulence. Supplements like FOS or inulin generally come in capsules or powder, but you’ll also find them combined with probiotics in a single formula. Since prebiotics are shelf-stable and naturally resistant to digestion, you don’t need to worry about enteric coating, refrigeration, or special delivery issues.

Beyond fiber
Although the standard definition of prebiotics focuses on soluble fiber that “feeds” the growth of beneficial bacteria, some experts think this definition should be expanded to include foods that promote gut flora in other ways. “We now understand that fiber isn’t the only food component that supports probiotic growth,” says Huffnagle. “Prebiotics work in a variety of other ways, including acting as selective antibiotics that slow down the bad microbes that good bacteria compete against for survival.”

According to Huffnagle, other main sources of prebiotics include:
• The fiber in oats, oat bran, barley, rice bran, apples, berries, and legumes acts as food for probiotic bacteria. “Different microbes eat different things,” says Huffnagle. “Probiotics tend to like soluble fiber, while harmful bacteria don’t.”
• Dietary phenols. According to Huffnagle, phenols support friendly flora by inhibiting the growth of harmful bacteria. They’re found in legumes, tea, red wine, fruits, berries, and dark chocolate.
• Polyunsaturated fatty acids. Some animal studies suggest that polyunsaturated fatty acids may function as prebiotics to a small degree, again by inhibiting the growth of pathogens. Examples of food sources include nuts, seeds, several vegetable oils (such as soy, safflower, corn, and sunflower), and fatty fish, like salmon, tuna, and herring.
These foods, as well as those high in inulin and FOS, provide an ample feast for friendly flora to thrive on. And probiotics are one dinner guest you want to stick around.

The Prebiotic Advantage
Prebiotics keep us healthy in myriad ways: They encourage the growth of beneficial bacteria; work hand-in-hand with probiotics to reduce the risk of several diseases; and also have specific actions of their own. Some highlights:

Intestinal health. Prebiotics increase fecal bulk, shorten transit time in the intestines, and relieve constipation. They also help treat Crohn’s disease and other inflammatory bowel diseases by reducing inflammation and encouraging the growth of lactobacilli and bifidobacteria.
Lower cholesterol. Research suggests that prebiotics enhance the cholesterol-lowering actions of probiotics, and help reduce cholesterol and blood lipids in their own right. “Prebiotics help probiotics break down cholesterol in the gastrointestinal tract, but also since some prebiotics are forms of fiber, they have the same cholesterol-lowering effects as soluble fiber,” says Huffnagle. The fiber does this, most likely, by binding to cholesterol and escorting it from the body, he says.

Colorectal cancer. “Prebiotics may help reduce harmful microbes that are causing inflammation or producing carcinogens,” Huffnagle says. Also, by binding up carcinogens in the gastrointestinal tract and stimulating peristalsis and elimination, prebiotics further help prevent and treat colorectal cancer.
Immune system. Some preliminary studies suggest that prebiotics can improve resistance against infection, says Glenn Gibson, PhD, professor of food microbiology and head of the Food Biosciences Department at the University of Reading, England. They accomplish this by providing food for probiotics, which make the immune system function more efficiently by “training” it to mount a speedy response to pathogens, clear them from the body, and then “calm down” again.

Bone health. Inulin in particular appears to enhance the uptake of calcium, probably both by increasing water in the bowel and boosting the volume of fluid in which calcium can dissolve and by acidifying the colon and, thus, raising the concentration of calcium.