Fruits and Vegetables — Do More Really Matter for Cancer Prevention?
By Maggie Moon, MS, RD
Consuming more fruits and vegetables in the hopes of preventing cancer seems futile, at least according to media coverage of recent findings published in the Journal of the National Cancer Institute. With headlines running contrary to major public health campaigns encouraging people to eat more fruits and vegetables, it’s easy to see why some people might be confused. Here, RDs with expertise in cancer research and prevention put the situation in perspective.
The EPIC Study
The results in question come from the large European Prospective Investigation Into Cancer and Nutrition (EPIC) study, which involved nearly 480,000 people who were followed for an average of nine years. In the context of inconsistent results, the researchers set out to test the widely held belief that eating fruits and vegetables can reduce the overall risk of developing cancer. They looked at subjects’ cancer risk in combination with total fruit, total vegetable, and total combined fruit and vegetable intake from 1992 to 2000. They collected detailed diet and lifestyle information as well as cancer incidence and mortality data.
From a study population where only 20% met the recommendation to eat five servings of fruits and vegetables per day, eating an extra 1.5 to two servings of fruits and vegetables (200 g) was related to a statistically significant 2.5% risk reduction for any cancer. More benefits were seen in heavy drinkers, though only for the cancers caused by smoking and alcohol.
“Small percentages are real, and I'll take them,” says Diana Dyer, MS, RD, farmer and author of A Dietitian’s Cancer Story. In a blog response to the EPIC study, Dyer puts things in perspective: “I would rather be nuancing over the choice of variety of apple, how it tastes, whether it is locally grown or shipped in from another state, organically grown or not, etc, etc, in contrast to debating the side effects of various chemotherapy regimens that may also offer only a few small percentage points of potential benefit and/or difference between them (ugh—been there, done that, twice, not fun).”
Alice Bender, MS, RD, nutrition communications manager at the American Institute for Cancer Research in Washington, D.C., agrees that small percentages are meaningful, adding, “I’m surprised that reports on the study were so negative, considering that the benefits of reaching recommended fruit and vegetable intake would be up to 11%.”
“Even a modest preventive effect of fruits and vegetables is a good message,” says Denise Snyder, MS, RD, CSO, LDN, a clinical trials manager at the Duke University School of Nursing, whose research has involved lifestyle interventions in cancer survivorship over the past 10 years. “If we dig a little deeper, this study showed that among the people who ate the most fruits and vegetables (six-plus servings daily), they had a 30% decrease in heart disease or stroke in addition to the 11% reduced incidence of all cancers.”
The study’s strengths are that it is large, well designed, and tackles a topic that is of major interest to dietitians, nutritionists, and other health professionals, says Veronica McLymont, MS, RD, CDN, director of food and nutrition services at Memorial Sloan-Kettering Cancer Center in New York City. “However,” she says, “self-reported data in studies on dietary and lifestyle habits may have inherent biases.” Bender adds that lumping all cancers together may mute the benefits for specific cancers where fruits and vegetables have a strong role, citing cancers of the pharynx, mouth, larynx, lung, stomach, and esophagus.
McLymont notes that even though the results show only a small inverse association between the total intake of fruits and vegetables and cancer risk, “more important is that a healthy diet with plenty of fruits and vegetables has many other health benefits.” She would like to see the EPIC study results serve as a catalyst for deeper exploration of this topic and not used to change clinical practice.
As RDs, we know that more really does matter when it comes to fruit and vegetable intake, and the recent EPIC study findings don’t change that. As Bender notes, “It can be confusing for patients who see all these headlines shift, so it’s important for RDs to continue to put them into context.”
— Maggie Moon, MS, RD, is a nutrition writer based in New York City who also works as a supermarket RD, consultant, and guest speaker.
The American Institute for Cancer Research responds to the EPIC study: www.aicr.org/site/News2/432850377?abbr=pr_&page=NewsArticle&id=
Diana Dyer, MS, RD, farmer and author of A Dietitian’s Cancer Story, responds to the EPIC study: www.dianadyer.com/2010/04/dont-throw-baby-out-with-bathwater.html
Walter Willet, MD, PhD, of the Harvard School of Public Health, published an editorial that ran with the EPIC study: “Fruits, Vegetables, and Cancer Prevention: Turmoil in the Produce Section”: http://jnci.oxfordjournals.org/cgi/content/full/djq098