Latest Results From Two Large Diet-Cancer Studies

Main Category: Cancer / Oncology
Also Included In: Nutrition / Diet
Article Date: 03 May 2007 - 12:00 PDT

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Today, experts at the American Institute for Cancer Research (AICR) welcomed preliminary results from two ongoing investigations into the links between diet and cancer.

Scientists working on two different cohort studies, the NIH-AARP Diet and Health Study and the Hawaii Multiethnic Cohort Study, which track the diets and cancer rates of large groups of participants, announced new results at a cancer research conference in Los Angeles over the weekend.

In one study, eating more fruits and vegetables was associated with lower risk of head and neck cancers. In the other study, diets high in one specific type of compound that occurs in onions, apples and certain other plant foods were associated with lower risk for pancreatic cancer.

These new findings should be considered preliminary because they haven't yet been published in peer-reviewed journals, but they come from well-established cohort studies with proven track records.

"If these new results hold up after the review process, they will represent major contributions to our understanding of the diet-cancer connection," said AICR Nutrition Advisor Karen Collins, RD. "Both studies reinforce AICR standing advice, based on years of research, to consume a diet high in a variety of plant foods for optimal protection against cancer."

The NIH-AARP Diet and Health Study

In one set of results, from a survey of over 500,000 members of the American Association of Retired Persons (AARP), men and women over 50 who ate the most fruits and vegetables had less head and neck cancers (most of which arise in the tissues lining the mouth, nose and throat) than those who rarely ate those foods.

Five years ago, participants in the NIH-AARP study filled out a detailed survey about their food intake. Since that time, researchers have been keeping track of cancer incidence within this large cohort.

Those participants who reported eating six servings of vegetables and fruits for every 1000 calories they consumed in a given day had 29 percent less risk than those who ate just 1 and a half servings per 1000 calories they consumed per day.

Since most of us consume around 2000 calories per day, the 29 percent protection observed in the study would be expected to occur in individuals who eat 12 servings of fruits and vegetables per day, compared to those who eat just 3 servings per day.

Less than a quarter of Americans manage to eat just 5 servings of fruits and vegetables per day, according to USDA statistics.

The NIH-AARP researchers say that, if you eat an average of 2000 calories per day, adding just two servings of fruits and vegetables could lower your risk of head and neck cancers by 6 percent. That may not sound like significant protection (especially when compared to the enormous protection afforded by simply avoiding tobacco, the chief cause of these cancers) but keep in mind that these cancers are responsible for more the 13,000 deaths in the U.S. each year.

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The Hawaii Multiethnic Cohort Study

Another set of results announced over the weekend comes from a study involving over 183,00 residents of Hawaii and California. The participants filled out a detailed food frequency questionnaire, and researchers followed them for an average of eight years, over which time 529 cases of pancreatic cancer were reported.

When scientists analyzed the reported food intake of study participants, they found that those who ate the most foods containing natural compounds called flavonols had a 23 percent reduced risk of developing pancreatic cancer than those who at the least.

Among smokers, who are at a heightened risk for pancreatic cancer, the risk reduction was more pronounced about 59 percent.

The study was the first to examine intake of three specific flavonols in respect to pancreatic cancer: kaempferol (found in spinach) quercetin (found in apples and onions) and myricetin (found in berries and red onions.) These substances have displayed anti-cancer activities in laboratory investigations, but results from human studies have been inconsistent.

Generally, kaempferol was associated with the most "across-the-board" protection (i.e., for smokers and non-smokers alike) but total flavonol intake was more strongly associated with lowered risk among current smokers.

The results were presented at the Annual Meeting of the American Association for Cancer Research (AACR) in Los Angeles. AACR is a large professional organization with a membership of thousands of cancer researchers. It is not affiliated with the American Institute for Cancer Research (AICR), which is an independent cancer charity that fosters research on the diet-cancer link and educates the public about the results.

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The American Institute for Cancer Research (AICR) is the cancer charity that fosters research on diet and cancer and educates the public about the results. It has contributed more than $82 million for innovative research conducted at universities, hospitals and research centers across the country. AICR also provides a wide range of educational programs to help millions of Americans learn to make dietary changes for lower cancer risk. Its award-winning New American Plate program is presented in brochures, seminars and on its website, http://www.aicr.org. AICR is a member of the World Cancer Research Fund International.