People in Africa and Southeast Asia depend on sorghum as a staple in their diets. Producers in the southern and central United States use it for livestock feed. It's available and fairly cheap, but not as nutritious as tannin-free grains.
"With a high-tannin diet, there can be as much as a 20 percent to 50 percent decrease in weight gain," Adeola says, who reported his findings in July at the national meeting of the American Society of Animal Science.
When Adeola investigated the problem, he found that tannins attach themselves to certain digestive enzymes bound to the membrane of the small intestine. Unfettered, the enzymes snag passing proteins and carbohydrates, break them down into amino acids and sugars, and make them available to go into the animal's bloodstream. When bound to tannins, however, the enzymes are unable to catch and break down passing food molecules. Potential nutrition passes through instead of being absorbed.
Adeola would like to foil the tannins. "Right now, any remedy is still speculative," he says. "But when we understand the whole picture, we may be able to look for agents that could reverse or decouple the binding between tannins and enzymes."
Writer: Rebecca J. Goetz