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Should You Eat More Vegetables to Prevent Cancer?

The EPIC Study Questions Usual Diet Cancer Advice

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Updated March 14, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Purple and Red Tomatoes

Purple and Red Tomatoes Are Cancer Fighting Foods

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Headlines about the European Prospective Investigation into Cancer and Nutrition (EPIC) study question the age old advice to eat more vegetables:

  • "Fruits and vegetables have only weak effect in cancer prevention."
  • "Cancer protective effect of fruits and vegetables may be modest at best."
  • "Fruits and veggies have small effect on cancer risk."

If eating more fruits and vegetables doesn't prevent cancer, why bother? Before you go back to the meat and potatoes of years past, you'd better read the fine print.

Unconventional Diet Views Sell News

You hear one thing, then news comes saying something different. It's not shocking if you're confused. Remember this: Selling news is a business. Whatever sells wins the top headline spot. And "unexpected" headlines sell. So, some news -- particularly health news -- may be reported without context, or even hyped up (or downplayed) to an unfortunate extent.

Dr. Ralph Moss, PhD, who runs the well-respected Cancer Decisions website points out: "According to the EPIC study, conversion to a moderately high fruit-and-vegetable diet could ideally save hundreds of thousands of people from getting cancer each year. This astonishing fact was hardly conveyed by the negative press reports on the EPIC study."

The study suggests that one apple per day could prevent about 36,000 cancers per year. Moss asks, "Is it a small thing to keep more than 36,000 Americans from getting cancer at such a minimal cost?"

For those touched by cancer, preventing 36,000 cancers a year is a very big deal.

Do Reporters Know Their Stuff?

Most journalists are not trained scientists. That is not to say that prevents them from reporting on science accurately. Many are well-skilled in this regard and/or have fact-checking colleagues to confirm the accuracy of their work. Still, others may not have such knowledge or resources. And in this fast-paced media world, health news may get reported in a way that fails to put it into perspective.

There are thousands of studies on fruits and vegetables and cancer. The vast majority of media coverage on the topic suggests that the EPIC study is the definitive answer on diet and cancer prevention. It's not.

Which Cancer?

What about the type of cancer? EPIC looked at all cancers lumped together. Research shows that fruits and vegetables protect against some, but not all cancers.

If we lump all cancers together, including those least likely to be related to diet, we can't see an effect of fruits and vegetables on risk.

Cancers most convincingly related to diet include those of the colon and rectum, stomach, mouth, pharynx and larynx, esophagus, and lung.

Colorectal cancer alone takes the lives of approximately 50,000 Americans every year. It is the second leading cause of cancer death in the United States.

Have You Been There?

When I read a news story that pooh-poohs the benefits healthy habits for beating cancer, I consult Diana Dyer, MS, RD. She's a friend, colleague, scientist and dietitian.

Even more, Diana is a 3-time cancer survivor. After one childhood cancer and two instances of breast cancer, she knows a lot about cancer. In her blog about the EPIC study, Diana discusses things that people touched by cancer should consider:

  • Cancer is a tough task master.
  • Not all cancer is preventable.
  • Risk reduction is the name of the game.
  • Do not put all your eggs (or fruits and vegetables) in one basket.
  • Don't look for one 'magic bullet.'
  • Cancer risk reduction needs to be multi-focused by creating a healthy lifestyle that consists of quitting (please don't start!) smoking, working toward achieving or maintaining a healthy weight, daily exercise, finding an enjoyable way to handle the stresses in life (we all have 'em!), and eating a healthy diet filled with healthy foods.

She also stresses, "small percentages are real, and I'll take them."

Real Life Doesn't Lend Itself to Research

Consider that EPIC is an observational study. This means researchers collect information from study participants and follow them for a time to see who gets a particular condition or disease.

This is different from a controlled trial in which some people are "assigned" to a particular intervention, such as taking a medication or following a diet plan. Randomized controlled trials are the "gold standard." They yield results that are more likely to uncover a relationship between cause and effect, if it exists. Unfortunately, real life doesn't lend itself to randomized controlled trials.

Nearly all of the large-scale, randomized nutrition studies of the last few decades have had problems keeping the intervention group on the intervention diet. Sadly, almost nobody can be asked to eat a healthy diet for research purposes and actually stick to it.

We are left with observational studies, like EPIC. These are imperfect. They are, however, better than nothing. But we have to put them into context.

Regardless of the recent headlines, most research evidence points to fruits and vegetables for reducing risk of several cancer types. And heart disease. And stroke. And hypertension. And diabetes...

For nutrition and cancer prevention, solid advice still remains: Eat more vegetables!

Sources

American Institute for Cancer Research. In the News: Does an Apple (or Two) a Day Keep Cancer Away? Accessed April 15, 2010. http://www.aicr.org/site/News2/432850377?abbr=pr_&page=NewsArticle&id=18541&news_iv_ctrl=1102&fp20100407

Boffetta P, Couto E, Wichman J, Ferrari P, Trichopoulos D, Bueno-de-Mesquita HB, et al. Fruit and Vegetable Intake and Overall Cancer Risk in the European Prospective Investigation Into Cancer and Nutrition (EPIC). J Natal Cancer Inst. Epub ahead of print April 6, 2010.

Diana Dyer, MS, RD. Don’t Throw the Baby Out with the Bathwater! Accessed April 14, 2010. http://www.dianadyer.com/2010/04/dont-throw-baby-out-with-bathwater.html

The World Health Organization. Global Strategy on Diet, Physical Activity and Health. Cancer: diet and physical activity’s impact. Accessed April 15, 2010. http://www.who.int/dietphysicalactivity/publications/facts/cancer/en/

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