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Last Updated: Nov 12th, 2006 - 20:38:00 |
World's Most Comprehensive Cancer Study
is Finding Connections Between
Dietary Patterns, Risk for Cancer
So Why Haven't You Heard of it?
WASHINGTON, DC -- The most far-reaching study of the relationship between diet and cancer ever conducted has been going on for over a decade, has produced over 70 published scientific papers (including 17 so far in 2006) and is exposing links between specific dietary patterns and the risk for getting cancer.
And no one in the US knows about it.
To the cancer experts at the American Institute for Cancer Research (AICR), the nation's leading authority on the link between diet and cancer, the EPIC study is vital. Although AICR is not involved with the huge, ongoing study, they look with great interest to its findings, which appear regularly, if quietly, in U.S. scientific journals.
"We believe this study represents a unique opportunity to find and map the specific connections between diet and chronic disease that other, smaller studies have had a harder time detecting," said Ritva Butrum, Ph.D., AICR Scientific Advisor. "It's time this ambitious project got the US attention it deserves."
The study is called the European Prospective Investigation into Cancer and Nutrition, or EPIC. A cohort study initiated in 1992, EPIC is currently tracking the diets and disease rates of an unprecedented 521,483 individuals in 10 different European countries. (See Table I to compare EPIC's size and methods to its better-known US cousins.)
Europe as "Vast, Living Laboratory"
Diet-cancer cohort studies work best, Butrum says, when two conditions are met:
1. there are enough participants to allow a comparatively rare disease like cancer to show up in sufficiently large numbers of study subjects, and
2. the participants' diets are different enough from each other to make comparing their intakes of specific foods possible.
Given EPIC's over half million participants, the grim truth is that nearly 40,000 cancer cases have already occurred in the study population, a figure which will continue to rise as the study continues.
And unlike the US diet, which features uniformly narrow ranges of intake for many foods, the European diet is a study in contrasts.
"The fact that diets differ so greatly across Europe -- think of Norway vs. Greece, for example -- makes the continent a vast, living laboratory, perfect for studying the effect diet on disease," says Elio Riboli, Ph.D., of Imperial College in London. Dr. Riboli coordinates the EPIC project, which is based in 24 centers throughout France, Greece, Norway, Denmark, Germany, Sweden, the Netherlands, the United Kingdom, Italy, and Spain.
Blood Samples Are Key
But it isn't simply the sheer size and international scope of the EPIC project that excites AICR researchers. They praise EPIC's comprehensive method of collecting dietary information and its rigorous study design, which includes internal methods of verification such as food diaries to help EPIC researchers standardize and validate their results.
The AICR experts note that, in addition to collecting information about diet and body measurements, EPIC researchers also collected blood samples from each one of its participants
"Collecting and storing blood samples is a daunting and expensive task, and that's why US cohorts tend to stick to questionnaires only, or collect from small subsets of study participants," said Butrum. "EPIC researchers have access to over half a million blood samples, and this vast store of data allows for an unprecedented level of analysis."
Specifically, the EPIC researchers are using the blood data to:
· Verify the diets of subjects by checking their self-reported dietary intake against blood levels of various food components;
· Correlate blood levels of specific food components (such as carotenoids or fatty acids) with cancer rates;
· Determine, through DNA analysis, how the subtle genetic differences that occur among individuals influence susceptibility to cancer;
· Reveal, for the first time, the role of newly emerging factors that affect cancer risk, such as hormones other hormone-like substances in the blood;
Major Findings Strengthen Diet-Cancer Link, More to Come
Since the very first results from EPIC were made public in 2001, nearly 80 studies growing out of EPIC have been published in such scientific journals as the Journal of the National Cancer Institute, the Lancet, the Journal of Nutrition, and many others.
These papers have examined associations between a host of factors in addition to specific aspects of diet, including hormone levels, body weight, genetic variation, air pollution and levels of physical activity.
Earlier this year, in a paper published in the March 1 issue of the Journal of the National Cancer Institute, EPIC researchers published data on meat intake and risk for stomach and esophageal cancers.
The researchers concluded that consumption of meat sharply increased risk of stomach cancer and esophageal cancer. For every 100 grams of meat consumed by subjects, risk for stomach cancer more than tripled. (Note: 100 grams of meat is approximately 3 ½ ounces.) In addition to total meat, intakes of red meat and processed meat were each independently associated with incidence of stomach cancer, though less strongly.
The authors also found that the association between meat intake and stomach cancer was considerably stronger among subjects with populations of H. pylori bacteria in their stomachs. For every 100 grams of meat consumed by subjects with H. pylori, their risk of stomach cancer was 5 times higher. (Although about 2/3 of the world population is infected by H. pylori, in Europe and the U.S. the infection rate is thought to be closer to 25 percent.)
Another recent finding from EPIC was published in the July 5, 2006 issue of the Journal of the National Cancer Institute. In the article, EPIC researchers found that two indicators of abdominal obesity, waist circumference and waist-to-hip ratio, were strongly associated with colon cancer risk in both sexes. Men with the largest waist circumference had 39 percent higher risk of colon cancer than men with the smallest, for example, while women in the study with the largest waist circumference has a 48 percent higher risk than women with the smallest waists.
A study appearing in the August 1, 2006 issue of the International Journal of Cancer analyzed the blood of 1,141 EPIC participants with breast cancer and compared it to the blood of 2,204 matched subjects without breast cancer. Among women over 60 whose blood was given under "non-fasting" conditions, high levels of serum C-peptide – a state of affairs that could reflect "insulin resistance," long suspected of contributing to cancer risk – was associated with a doubling of breast cancer risk.
In a study scheduled for publication in September, EPIC researchers will report that risk for oral and pharyngeal cancers drop by 9 percent for every 80 grams of vegetables and fruits consumed per day. (Note: 80 grams is approximately a single serving. The average American consumes approximately 4 servings, or 320 grams, of vegetables and fruits per day.)
As these data begin to mount, Dr. Riboli is already noticing the emergence of some definite trends.
"Certainly we can say that globally, diets that are high in fruits, vegetables, fiber and fish are associated with greater protection against cancer in general," he says.
"We also see that obesity and sedentary lifestyles are shaping up to be much larger factors in increasing cancer risk that was previously thought," Riboli continues. Diets high in meat, especially processed meats such as cold cuts, hot dogs, bacon and sausage are also consistently associated with higher risk, he says.
Riboli admits that the associations between diet and cancer observed so far haven't been uniformly strong, but points to the fact that the study only published its first results in 2001. As time goes on and occurrences of cancer increase in the study population, it's likely that links will become easier to observe. He also stresses EPIC's unique ability to analyze "multi-factoral" models – overall dietary patterns – in addition to links to specific foods in isolation such as fish, vegetables, meat, etc.
Major International Findings Have a Tough Time Making Their Way Stateside
Asked why so few Americans have heard about the largest diet-cancer project ever undertaken, Riboli is philosophical. "We don't do this for the attention," he says with a shrug.
For their part, the AICR experts who follow EPIC so closely suspect that in science, as in most things, Americans tend to adopt a "Made in America" mindset. Research conducted in the US generates buzz and attention, while major international studies can sometimes get discounted, or dismissed outright.
"Despite its breathtaking scope, EPIC is a study that's only now coming into its own," said AICR's Butrum. "It doesn't yet have the track record of the better-known US cohorts, but it's building it up, paper by paper. Now is the time to start paying attention."
* * *
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 $78 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, www.aicr.org. AICR is a member of the World Cancer Research Fund International
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