A diet high in flavonols — chemicals found in broccoli, onions, apples and berries — cut the risk of pancreatic cancer by 23 percent compared with people who ate the least, said a study of 183,500 people living in California and Hawai'i presented Sunday at the Los Angeles meeting.

Smoking is known to increase risk of pancreatic cancer, according to the study's lead author, Ute Nothlings, a researcher at the German Institute of Human Nutrition Potsdam- Rehbruecke. To see which foods may be protective, people filled out questionnaires, then were followed an average of eight years. Pancreatic cancer kills about 32,000 people a year, according to the American Cancer Society.

"Short of stopping tobacco use, it has been difficult to consistently show lifestyle factors that might help protect against this deadly cancer," Nothlings said in a statement.

Pancreatic cancer is one of the most deadly of cancers because it spreads rapidly and is rarely diagnosed early, according to the Mayo Clinic Web site. The only way to eliminate the cancer is through surgery.

Head and neck cancer

Another study of 500,000 people age 50 and older presented at the meeting found those who said they ate one extra serving of fruits and vegetables a day reduced their risk of developing head and neck cancer.

Researchers from the National Cancer Institute said people who ate the most fruits and vegetables, about 12 servings a day for people who take in 2,000 calories a day, had a 29 percent lower risk of getting head and neck cancer than people who consumed the least amount, one and a half servings a day.

One medium size fresh fruit, or six ounces of fruit juice equals one serving.

The study, sponsored by the National Institutes of Health, used questionnaires from AARP members and followed them for five years. It produced a large volume of data, with about 800 respondents who developed head and neck cancer, said Neal Freedman, cancer prevention fellow at the National Cancer Institute.

Head and neck cancer is the sixth-leading cancer killer worldwide, causing 350,000 deaths a year, according to the National Cancer Institute.

"The more people consumed, the less their risk was," said Freedman, lead author of the study.

Breast, ovarian cancer

A separate study at UCLA found that two chemicals in broccoli and soy stopped the spread of breast and ovarian cancer cells in laboratory studies.

The chemicals, called DIM and genistein, interfered with proteins that act like engines for migration of breast and ovarian cancer in the body, researchers said. If proven in further tests in animals and humans, researchers said the vegetables could enhance existing treatments.

The amount of chemicals used in the tests was comparable to a high dose of supplements, researchers said. People likely would not be able to eat enough of the foods to get the protective effect, researchers said.