The study, appearing this week , is based on interviews with 238 men with prostate cancer and 471 men who were free of the disease.

Men in the study, all residents of Shanghai, China, were asked how frequently they ate 122 food items.

The results showed that those who ate more than a third of an ounce (nine grams) a day from the allium food group were about 50 percent less likely to have prostate cancer than those who ate less of the foods. The allium food group includes garlic, scallions, chives, leeks and onions.

Scallions seemed to be the most protective. According to the study, men who ate about a tenth of an ounce or more a day of scallions reduced their prostate cancer risk by about 70 percent. For garlic consumption of the same amount, the prostate cancer risk was reduced by about 53 percent.

"The reduced risk of prostate cancer associated with allium vegetables was independent of body size, intake of other foods and total calorie intake and was more pronounced for men with localized than with advanced prostate cancer," the study authors reported.

The authors acknowledged that there were "several potential limitations" to the study, including its dependence on self-reported food consumption data.

The study was conducted by researchers at the National Cancer Institute, one of the National Institutes of Health, and at the Shanghai Cancer Institute in Shanghai, China.

(Agencies, November 7, 2002)