Spring 2008

Research You Can Use Today

This quarter, we’re featuring four studies published in the last six months. Each is followed by commentary from Cancer Prevention Clinic physicians.

Low-fat diet and cancer trial

Is That So? Everything Does NOT Cause Cancer

Cancer Prevention Tip: Quit Smoking

Aspirin, folic acid, and prevention of recurrent colorectal adenomas

The goal of this study, which was published in the January 2008 issue of Gastroenterology, (134[1]:29-38), was to better understand if regular aspirin use and dietary folate reduced the risk for colorectal neoplasms, which can lead to colon cancer.

All patients had an adenoma removed in the six months before the study and were followed-up at four-month intervals with a second colonoscopy after approximately three years. For the 945 patients recruited into the aspirin study, 853 (90.3%) underwent a second colonoscopy. In total, 434 patients received 300 mg per day of aspirin and 419 received a placebo. The results: 99 (22.8%) of those who took aspirin had a recurrent adenoma as compared to 121 (28.9%) who took the placebo. A total of 104 patients developed an advanced colorectal adenoma; 41 (9.4%) of these were in the aspirin group and 63 (15%) were in the placebo group.

Folate supplementation was given in a similar method at 0.5 mg per day, but was found to have no effect on adenoma recurrence. The study authors concluded that 300 mg a day of aspirin, but not folate does reduce the risk of colorectal adenoma recurrence, with evidence that aspirin could have a significant role in preventing the development of advanced lesions.

CPC COMMENTARY: This study suggests that taking aspirin may reduce the risk of colon adenomas, which can change into colon cancers. We suggest discussing the risks and benefits of aspirin with your doctor before taking aspirin regularly for this purpose. There is no role for folate supplements to prevent colorectal cancer.

Fruits, veggies, tea and ovarian cancer risk

The International Journal of Cancer published a study last November [121(10):2225-32, 2007 Nov 15], that looked at flavonoids, the antioxidant compounds found in fruits, vegetables, tea, and ovarian cancer risk.

There has never been a study that looked at this antioxidant and ovarian cancer risk. So this study analyzed the association between five common dietary flavonoids and the incidence of epithelial ovarian cancer among 66,940 women in the Nurses’ Health Study. Their analysis included 347 cases diagnosed between 1984 and 2002, and 950,347 person-years of follow-up.

While there was no clear association between total intake of the five flavonoids examined and incidence of ovarian cancer, there was a significant decrease (40%) in ovarian cancer incidence for the highest versus lowest amount of kaempferol intake and a significant decrease (34%) in the incidence for the highest versus lowest amount of luteolin intake. Also, there was evidence of an inverse association with drinking non-herbal tea and broccoli, the primary contributors to kaempferol intake in our population.

The study authors concluded that eating or drinking certain flavonoids may reduce ovarian cancer risk, although additional studies are needed to further evaluate this association. If confirmed, these results would provide an important target for ovarian cancer prevention.

CPC COMMENTARY: Flavonoids are found in virtually all fruits, vegetables, herbs, and spices. They are also found in dry beans (they give red beans, black beans, and speckled beans their color), and grains. Products made from these foods (wines made from grapes, for example,) also typically contain a wide variety of fl avonoids. This study suggests that a diet rich in foods with high flavonoid content might help reduce one’s risk of ovarian cancer. We do not recommend flavonoid supplementation, however, beyond what can be obtained in a healthy diet.

Cereal fiber may reduce risk of gastric cancer

There have been several studies that suggest dietary fiber may reduce the risk of gastric cancer, but this has not been confirmed. One study reported reduced risk of one type of gastric cancer associated with cereal fiber, but not with fruit or vegetable fiber. To date, different food sources of fiber have not been examined with respect to other types of gastric tumors.

The International Journal of Cancer published a study [121(7):1618-23, 2007 Oct 1] that examined the association between fiber from different food sources and the incident of gastric adenocarcinomas (GC) among 435,000 people from 10 countries participating in the European Prospective Investigation into Cancer and Nutrition study. The subjects aged 25-70 years completed dietary questionnaires in 1992-98, and were followed up for a median of 6.7 years.

In that time, about 312 gastric cancers were observed. Intake of cereal fiber, but not total fruit or vegetable fiber, was associated with reduced gastric cancer risk and there was a strong inverse association for diffuse, but not intestinal type tumors. So, the study authors concluded that eating cereal fiber may help reduce the risk of gastric cancer, particularly diffuse type tumors. But, further study on different food sources of fiber in relation to gastric cancer risk is needed.

CPC COMMENTARY: Recent studies suggest that dietary fiber does not protect against colorectal cancer, but this large study suggests that cereal fiber might reduce one’s risk for gastric cancer. As gastric cancers are rare, we do not recommend increasing one’s cereal fiber intake solely to prevent this cancer.

Low-fat diet and cancer trial
The Women’s Health Initiative Dietary Modification (DM) Randomized Controlled Trial evaluated the effects of a low-fat diet on ongoing (chronic) diseases, with breast cancer and colorectal cancer as their primary focus.

Published in the Journal of the National Cancer Institute[99(20):1534-43, 2007 Oct 17], the trial also listed ovarian cancer and endometrial cancer as outcomes that may be favorably affected by a low-fat diet.

The study looked at 48,835 postmenopausal women who were randomly assigned during 1993-1998 and followed up for an average of 8.1 years. The intervention goal was to reduce total fat intake to 20 percent of energy and to increase consumption of vegetables, fruits, and grains. Cancer outcomes were verified by pathology report review.

The results showed that ovarian cancer risk was lower for women with a low-fat diet, but the risk did not differ until 4 years after the start of the diet. Risk of cancer of the endometrium did not differ between the groups. The estimated risk of total invasive cancer was slightly lower in the intervention group than in the control group and so the study authors concluded that a low-fat diet may certainly reduce the incidence of
ovarian cancer among postmenopausal women.

CPC COMMENTARY: A low fat diet may reduce a woman’s likelihood of developing ovarian cancer, but she must stick with the diet for many years to achieve a benefi t. As there are other reasons to have a low-fat diet, we recommend such diets for all of our patients.

Is That So? Everything Does Not Cause Cancer

There’s a strong misconception with Americans that “everything causes cancer.” Studies have also shown that Americans say cancer is their number one health concern yet they believe it is impossible to prevent. They believe cancer is beyond their control.

Nutrition Advisor Karen Collins from the American Institute for Cancer Research (AICR) calls these misconceptions “distressing.” “Popular frustration about cancer is on the rise. An ‘everything causes cancer’ mindset is taking hold, which causes Americans to throw up their hands and overlook the steps that can lower their risk.” According to a study the AICR conducted in 2007 called Facts vs. Fears Survey, most Americans don’t realize that they can lower their cancer risk by eating healthy foods, getting more exercise, and managing their weight.

Only a third of American adults in the United States realize that diets high in red meat increases one’s risk for cancer (most specifically, colon cancer). Nearly the same small number of people know that alcohol is also linked to cancer, (specifically colorectal, breast, esophageal, mouth, larynx, and pharynx cancer). Less than half of Americans realize that there is strong evidence linking being overweight and obesity as risk factors for eight different cancers, including colon, rectum, and breast cancer.

Most people believe that cancer is out of their control and that pesticides, food additives, and hormones in beef are the primary causes for cancer. Research however says the links between these factors and cancer is low and that there is a lot one person can do to minimize their risk for the disease.

AICR’s Second Expert Report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective, is the most comprehensive scientific analysis of cancer prevention and causation ever undertaken, authored by an international expert panel that reviewed 7,000 research studies and classified the accumulated evidence for specific diet-cancer links. The report is online at www.dietandcancerreport.org.

Cancer Prevention Tip

Quit Smoking “Tobacco is the most addictive substance on the planet and cigarettes are the most highly engineered consumer product on the market,” says Dr. Abigail Halperin, director of the UW Tobacco Studies Program and physician at SCCA’s Smoke-Free Life Program.

“Cigarettes are designed for maximum addiction. They are also the only consumer product that, when used as directed, kills half of its users.”

Help is available!
SCCA’s Smoke-Free Life Program is designed to help you quit smoking and stay that way. Call 206-288-SCCA (7222) or call the Tobacco Quit line for help at 1-800-QUIT-NOW or in Spanish, 1-877-2NO-FUME (266-3863).

April 2008


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