Text B. Scientists Explain Why Vegetable Recipes Skimp on Spices

Text A. Tea Aids Oral Health

Divide into two groups. Each group should read either Text A or Text B about two unusual methods of fighting bacteria. Then in pairs discuss your text with the partner. Try not to miss any details.

Exercise 6. Fighting Bacteria.

By Sarah Graham

A spot of tea may offer more than just a pleasant way to pass the afternoon. Research findings presented this week at the 103rd General Meeting of the American Society for Microbiology in Washington, D.C. suggests that it can help fight bad breath and may boost the powers of toothpaste.

Christine Wu and Min Zhu of the University of Illinois at Chicago College of Dentistry isolated chemical components of tea leaves known as polyphenols and tested them against three species of bacteria known to cause bad breath. The researchers found that the compounds, specifically catechins and theaflavins, inhibited growth of the oral bacteria over a 48-hour incubation period. What is more, lower concentrations of the chemicals interfered with the enzyme that catalyzes the production of hydrogen sulfide, which has the notorious smell of rotten eggs, and reduced its production by 30 percent. The compounds studied by the scientists are present in both green tea and black tea, although they are more abundant in the latter.

In a second study, researchers reported that green tea may provide additional benefits. Milton Schiffenbauer of Pace University and his colleagues tested tea's ability to fight bacteria that cause infections such as strep throat and dental caries. They found that green tea extracts and polyphenols--particularly those from caffeinated beverages--inhibited bacterial growth. Adding these agents to toothpaste and mouthwash, he notes, may make them more effective at combating microbial agents. (From Scientific American Online, May 21, 2003)

By Kate Wong

Several years ago, a team of researchers from Cornell University proposed that the spices used in traditional meat-based cuisines originally served not as flavor, but to stave off bacteria and fungi. Now new research is providing further food for thought: findings reported in the June issue of Evolution and Human Behavior explain why vegetable-based dishes tend to lack such spiciness.

Plants, it turns out, don't require so much protection against microorganisms as meats because they have their own natural chemical and physical defenses, which continue to function after cooking. Cornell neurobiologist Paul W. Sherman and undergraduate Geoffrey Hash thus predicted that if spices first served as antimicrobials, especially in warmer climates, vegetable recipes in the same countries surveyed for the meat research should feature fewer spices. Subsequent investigation bore this out. Analyzing 2,129 traditional vegetable recipes from 36 different countries, the team found that spice usage was far lower than that found in meat-based dishes from the same cultures. Indeed, of the 41 spices considered, 38 appear more frequently in meat recipes; the three that don't fit this pattern - sesame, caraway and sweet pepper - offer little protection anyway.

"Humans have always been in a co-evolutionary race with parasites and pathogens in foods, and our cookbooks are the written record of that race," Sherman asserts. "We haven't had to 'run' as hard when we ate vegetables. We haven't had to use extra pharmaceuticals to make vegetables safe for consumption." (From Scientific American Online, July 11, 2001)

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