PHILADELPHIA -- A study has found the first direct evidence that the nutrient that makes tomatoes red may protect men against prostate cancer by shrinking tumors and slowing their spread.

The nutrient, lycopene, has emerged as one of the trendiest of all nutritional supplements in recent years.

Large population surveys have suggested that those who eat plenty of tomatoes -- the primary natural source of lycopene -- are less likely to get prostate cancer and some other malignancies.

To see if tomatoes are truly the reason why, researchers from the Karmanos Cancer Institute in Detroit gave lycopene capsules to men who were about to undergo surgery to remove their cancerous prostate glands.

The study involved 33 men who were randomly assigned to take lycopene or nothing for 30 days before their prostate operations. Before surgery, the volunteers showed no obvious signs that their cancer had spread.

After surgery, the doctors found that cancer tissue was less likely to extend clear to the edges of the lycopene users' prostate glands. And pre-cancerous cells in their prostates were less abnormal-looking.

"This suggests that lycopene results in a decrease of the tumor size and makes the cancer less aggressive," said Dr. Omar Kucuk, who directed the study.

The findings were presented in Philadelphia yesterday at a meeting of the American Association for Cancer Research.

Kucuk warned that his study is small, and cautioned against routine use of lycopene supplements without further evidence.

Lycopene pills are widely available.

In the study, financed by the Karmanos institute, volunteers were given two daily 15-milligram capsules of Lyc-O-Mato, a lycopene extract made by LycoRed Natural Products of Israel.

Kucuk said this is the amount of lycopene found in about a pound of tomatoes. However, since lycopene is not easily absorbed from raw tomatoes, it might take two or three pounds to actually raise blood levels as high as were seen in the study.

"The results are significant," said Dr. Frank Rauscher of the Wistar Institute. "It's remarkable that lycopene may have both therapeutic and preventative value."

Prostate cancer is the most common malignancy among American men. The American Cancer Society estimates that 179,300 men will be diagnosed with prostate cancer this year, and 37,000 will die from it.

Among the study's findings:

Cancer had spread to the very edge of the prostate gland or beyond in seven of the 21 men on lycopene, compared with nine of the 12 in the comparison group.

Levels of PSA -- prostate specific antigen, a measure of tumor activity -- fell 20 percent between the start of treatment and surgery in the lycopene patients. They were unchanged in the comparison group.

Pre-cancerous but worrisome tissue in the lycopene patients was also less abnormal-looking.

"If this is real, I would expect to see a decrease in the relapse rate and increased survival in these patients" taking lycopene, Kucuk said.

One of the most influential pieces of research on tomatoes and cancer was a large Harvard study released in 1995. It followed the eating habits of 47,000 men for six years. Those who had at least 10 weekly servings of tomato-based foods were up to 45 percent less likely to develop prostate
cancer.