Veggies defending themselves with valuable phytochemicals

By Pam Sowers
HS News & Community Relations

Brussels sprouts, grapefruit, cabbage, kale, mustard greens, arugula, spinach, dark chocolates, red wine and a lot of other typical Thanksgiving leftovers are proven to contain dietary phytonutrients. These nutrients have been associated with cancer prevention and other health benefits. As a review by a UW researcher shows, because these trace chemicals taste bitter, acrid or astringent, the food industry has devoted decades of work to removing these phytonutrients.

Dr. Adam Drewnowski, director of the UW Nutritional Sciences Program based in the School of Public Health and Community Medicine, says in a research review published this week by the American Journal of Clinical Nutrition that when it comes to phytonutrients, the demands of good taste and good health may be wholly incompatible.

“Many people don’t like to eat vegetables - and the feeling is mutual,” Drewnowski said. “Plants protect themselves against being eaten by secreting natural pesticides and other bitter-tasting toxins. In small amounts, the phenols, flavnoids, isoflavones and other chemicals are proving to be good for us.”

Unfortunately, a dislike of these flavors has been ingrained in most people by nature. Humans and other animals have long associated bitter or sour flavors with spoiled or poisonous food. That is why food manufacturers routinely remove these compounds from plant foods through selective breeding and a variety of debittering processes. Drewnowski said this is where science and gastronomy must come together.

The solution, Drewnowski said, is in using the wisdom found in Mediterranean cuisine. For generations, cooks in Greece, Italy and France have coped with bitter vegetables by seasoning them lightly with salt and dashes of olive oil. The oil in particular blunts the bitter flavors of phytonutrients.

The fact that the amount of bitter plant compounds in the current American diet is so small is a reflection of the achievements of the agricultural industry. Debittering foods, either chemically during processing, or by breeding bitterness out of such things as broccoli and zucchini, has been a focal point of the industry for decades.