AMES, Iowa (AP) -- Don't use a fat-free dressing on your salad, an Iowa State University researcher says. A bit of fat added to fresh vegetables helps bodies absorb cancer-fighting lycopene and alpha- and beta-carotenes, said Wendy White, an ISU associate professor of nutrition.

If vegetables remain free of fat, the body won't consume the essential nutrients that can help prevent cancer and heart disease, White's research shows.

About 2 fluid ounces, or four tablespoons, of salad dressing would be an adequate amount of dressing for a large salad, White said. Fans of add-ons such as cheese, bacon bits, fried chicken, egg yolk and avocados should opt for a fat-free dressing, she said.

"If a person is going to eat a brownie anyway with the meal, that's fine as long as it's done in moderation," White said. "In that case, I would go with fat-free dressing on the salad."

"That's good news for us," said Karen Boelling, who on Thursday was munching on a garden salad with a healthy dose of Parmesan dressing at Big Leagues Skybox Grill & Deli in downtown Des Moines. "I like the salad dressing. It makes it worth eating."

The results of the study, paid for by Procter and Gamble's Nutrition Science Institute, surprised Wells Fargo employee Laura Bock, who was eating a salad during lunch break Thursday.

"You always think of salad dressing as fattening and bad," she said.

White cautioned that too much dressing can lead to health problems.

"In the absence of fat, people are probably not deriving the benefits from the beta-carotenes and other carotenoids," White said. "They have to balance that knowledge, along with the knowledge that fat is excess calories, and excess body weight is a huge problem in America."

Nearly one-third of U.S. adults are obese, and 300,000 deaths each year can be linked to unhealthy eating and exercising habits, according to the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.

Copyright 2004 The Associated Press. All rights reserved.