Last Updated: 2003-06-04 10:00:05 -0400 (Reuters Health)

CHICAGO (Reuters Health) - Most Americans know there are ways to lower their risk of cancer, but many are confused about how to do it, according to a survey released at a major cancer meeting this week.

Among the 1,000 adults surveyed, the majority recognized that diet may play a role in cancer, but only 38 percent "strongly" agreed that they could reduce their cancer risk by eating a diet high in vegetables, fruits and fiber -- even though there's evidence that such healthful eating habits can cut the risk of some cancers.

Only about half of Americans surveyed agreed that they could reduce their risk of developing certain cancers with exercise.

"There is good evidence that exercise may play an important part in some cancers such as colon and breast," Dr. Bernard Levin, head of the American Society of Clinical Oncology's (ASCO) Cancer Prevention Committee, told Reuters Health.

Results of the survey, a joint effort by ASCO and the Cancer Research and Prevention Foundation, were released at ASCO's annual meeting here this week.

Only one-third of respondents felt that maintaining a healthy weight was important in cancer prevention.

On the contrary, maintaining a healthy weight is one of the best ways to reduce the risk of a number of cancers, including those of the colon, pancreas and breast, according to Levin. Recent research suggests that as many as one-third of all cancers may be related to obesity.

But Levin was particularly disturbed by the survey findings on sunscreen. Only about one-third of respondents said they always put on sunblock before going to the beach or pool.

"We know that skin cancer is one of the most preventable cancers and, in some parts of the country, one of the fastest growing," Levin said.

Thirty-four percent of those surveyed strongly agreed that they are at increased risk of developing cancer if a family member has had cancer, and nearly two-thirds said they or an immediate family member has had cancer.

On the vitamin front, nearly 30 percent felt strongly that taking vitamins or herbal supplements will reduce their risk of getting cancer.

"But, in fact, there are no scientific studies on herbal supplements that show they have any effect on reducing cancer risk," Levin said. "In general, the best way to get these nutrients is from their natural source, which is in the diet."

When it comes to tobacco, the vast majority of respondents knew that tobacco plays a role in causing cancer. However, 39 percent of those who said they have smoked continue to do so.

This shows a clear "discrepancy between belief and practice," Levin said.

Overall, according to Levin, the survey shows that "Americans need clear information on what they can do to reduce their risk of cancer."