Microbe Helps Evaluate Dietary Fiber

Scientists at the Richard B. Russell Agricultural Research Center in Athens, Georgia, brought in a small, new consultant last summer for an inside job. The assistant was microscopic and lived in people's intestines. It did not shrink from its task: eating indigestible pieces of food. The humble, mild-mannered microbe helped the scientists identify the best foods for a high-fiber diet.

Nutritionists have long preached the gospel of including fiber in the diet. It helps with weight control and may protect the colon from certain cancers. But everyone knows fiber-rich diets can sometimes lead to bloating and gas.

Nutritionists are still debating which fiber will work best with the least discomfort.

Perhaps a bacterium could provide some of the answers, suggested Scott Martin, an anaerobic microbiologist with the University of Georgia at Athens.

He shared his thoughts with Agricultural Research Service microbiologist Danny E. Akin and chemist W. Herbert Morrison at the nearby Russell center.

The trio began designing experiments to use bacteria from the human gut to evaluate fiber quality.

The microbe they picked: Bacteroides ovatus. It is one of the few human-dwelling, fiber-digesting bacteria that's been isolated.

The researchers found that B. ovatus tore through oat bran, dissolving almost 75 percent of a sample in 3 days. That means the oat bran may not be the best fiber candidate. If fiber breaks down too quickly, it can't provide the bulking and cleaning roles in the gastrointestinal system that nutritionists say are critical to human health.

Maize or corn bran was slowest to break down, with 42 percent digestion over the same period. But slowest breakdown may not be best to avoid the discomfort of intestinal gas.

Wheat bran struck a middle ground.

Finding that balance in digestibility might someday provide fiber supplements for consumers who can't deal with a morning bowl of high-fiber flakes. Researchers said they hope their initial work will be valuable to food producers and nutritionists for this reason. --By Jill Lee, Agricultural Research Service Information Staff.

Danny E. Akin and W. Herbert Morrison are in the USDA-ARS Quality Assessment Research Unit, Richard B. Russell Agricultural Research Center, 905 College Station Road, Athens, GA 30605; phone (706) 546-3482, fax (706) 546-3607.

"Microbe Helps Evaluate Dietary Fiber" was published in the August 1998 issue of Agricultural Research magazine. Click here to see this issue's table of contents.