Research Beginning to Reveal Clues About Impact of Diet on Cancer Survivors, Scientists Say
American Institute for Cancer Research
Survivors, Researchers Share Knowledge, Concerns at AICR Conference for Nutrition After Cancer
Hundreds of cancer survivors met today with some of the nation's top cancer experts to discuss the latest science on how diet and lifestyle affect the chance for cancers to return. At a conference called "Nutrition After Cancer," sponsored by the American Institute for Cancer Research (AICR), scientists told a roomful of cancer survivors, health professionals, policy makers and members of the media that science is beginning to uncover important answers.
Over the course of the daylong conference, survivors in attendance learned what science does - and does not - know about diet's ability to influence recurrence, secondary cancers, and late effects of cancer treatment. Conference speakers listened attentively to the specific concerns raised by survivors during extended Q and A sessions and vowed to renew and revise current research efforts.
"There are now over 8.5 million people living after cancer in the US alone," said Jeff Prince, Vice President for Education at AICR. "This number will continue to rise as efforts to screen and treat cancer continue to improve.
"Decades of research have revealed convincing evidence that diet, exercise and weight management can influence the risk of first cancers. Now, at last, science is beginning to focus on how these same factors may help survivors keep healthy and free of disease. We at AICR will do all we can to advance this long overdue and still woefully underfunded agenda."
At the conference, Prince announced that AICR, long known for its work in the area of diet and cancer prevention, is championing efforts to increase national awareness - and research funding - for nutritional strategies that may help prevent cancer recurrence and secondary cancers.
Some of the other speakers at the conference spoke about the dietary issues currently attracting the most attention and controversy in the survivor community: soy, flaxseed, exercise and body weight. One speaker outlined the overall research completed to date and highlighted areas that demand further attention. The conference was concluded by a UCLA researcher who offered survivors the scientific bottom-line: a daily plan for continued good health based on the most current science.
Survivor/Dietitian Lays Out Her "Personal Action Plan"
Diana Dyer, a registered dietitian and three-time cancer survivor who has written widely on survivor issues, began the conference by speaking at length about how she translates the science about diet and survivorship into a "personal action plan" for healthy living.
"Cancer treatment brings about profound physical and emotional changes," she said. "Most survivors come out of this very difficult experience determined to do whatever it takes to stay healthy. [After my most recent cancer treatment] I wanted everything I ate or drank to have some component that was going to reduce the cancer process if not help eliminate it. That meant my food was going to have to come from plants."
Dyer described her efforts to increase her already considerable consumption of vegetables, fruits and whole grains, outlined her daily exercise plan, and her avoidance of meat and alcohol. She noted that recent findings about fats have caused her to reassess some of her previous professional attitudes.
"It used to be so simple," she said. "Dietitians and doctors used to tell people to reduce the amount of fat in the diet, period. Well, now we understand that it is probably more important to look at the type of fat in the diet, not just the total amount."
In particular, monounsaturated fats found in olive or canola oil, as well as omega-3 fats from certain fish and flaxseed, are "important fats to have in the diet to reduce the cancer process. It's the other types of fat - saturated and trans-fats - that I'm trying to eliminate from my diet."
Dyer said she has established an endowment at AICR to specifically fund projects that will study nutritional strategies after a cancer diagnosis, to optimize odds for long term survival.
Researcher Presents "State of the Science"
At the AICR conference, Richard Rivlin, MD, Senior Vice President of the American Health Foundation, began his remarks by charting the tremendous progress that has been made in the prevention, early diagnosis and treatment of cancer in recent decades.
It was this very progress, Dr. Rivlin said, that has led to the emergence of the entirely new area of medicine, research and social policy called cancer survivorship. "The number of American cancer survivors now exceeds the annual number of new cancer cases and deaths," he said. "And as more and more people survive cancer, more and more practical questions arise."
Dr. Rivlin then outlined the new survivor-related dietary issues that scientists have begun to tackle in just the last few years.
Questions have recently arisen around antioxidants, he said, because cancer - and cancer treatment - can change some of the ways the body reacts to these substances. Research has shown that the same process for which these substances are prized (the so-called "scavenging" of potentially hazardous metabolic by-products, which has been linked to lower cancer risk) may actually increase the damage done by certain therapeutic agents.
Foods that have been shown to be cancer-protective for individuals who have never had cancer may prove to offer greater or lesser protection for survivors, Rivlin said. He added that scientists are paying particular attention to studies involving soy foods, flaxseed, selenium, and vitamin C. New information is emerging about the importance of exercise, weight management, and how closely body-fat percentage correlates with cancer incidence, and Rivlin believes this information will soon impact the dietary advice given to cancer survivors.
In the meantime, he referred survivors to the advice contained in AICR's Diet and Health Guidelines for Cancer Prevention (see below). Dr. Rivlin concluded his remarks by lauding AICR for its "research programs that are committed to providing evidence-based knowledge to enhance survivorship," but stressed that more organizations, more researchers, and greater funding are desperately needed.
Speakers Spotlight Current Controversies
Widely known soyfoods expert Dr. Mark Messina of Loma Linda University addressed the conflicting information about soy's role in the diet of cancer survivors.
"There are two opposing claims: soy is protective and should be recommended for consumption by breast cancer patients and soy is harmful and should be avoided by women with a history of or at high risk for breast cancer. No convincing data exist either way," he said.
"For years I suggested that women with breast cancer not consume soy, but I have changed my opinion in light of the most recent data on this topic. In my view, if women enjoy partaking of soy, I think it is reasonable for them to continue to partake of it. Unfortunately, however, I don't think there are sufficient data to specifically recommend that breast cancer patients begin to consume soy solely for the purpose of enhancing survival."
Messina went on to summarize the "intriguing but limited" animal and human data suggesting that soy may decrease risk of prostate cancer. "I think prostate cancer patients can certainly be encouraged to consume at least two servings of soy per day, " he said.
Following Dr. Messina's presentation, Dr. Wendy Demark-Wahnefried, a Ph.D. and registered dietitian at Duke University Medical Center, discussed new data on flaxseed. Flaxseed has only come under study in the last ten years, chiefly because it contains high concentrations of both omega-3 fatty acids and lignans, two substances that have shown dramatic anti-cancer potential in laboratory studies.
Recently, those preliminary results have been confirmed by clinical data, in which the presence of flaxseed in the diet reduced the growth of breast tumors in patients with estrogen-negative breast cancer. "But other trials involving patients with breast, prostate, colon and skin cancer have yielded mixed results," said Dr. Demark-Wahnefried, "and all studies to date have been short-term."
For this reason, she recommends that "cancer patients, particularly those with estrogen-receptor-positive cancer and those taking drugs like tamoxifen should eat flaxseed with caution. It is prudent that only moderate amounts of flaxseed - about one tablespoon per day - should be added to a healthy diet that is based on a large amount of plant foods and low amounts of fat and meat."
A review of research on body weight and its relationship to cancer development and cancer patient outcome was presented by medical oncologist Rowan Chlebowski, MD, PhD, of the Harbor-UCLA Research Education Institute.
"By conservative estimates based on observational studies, hundreds of thousands of otherwise avoidable, potentially lethal cancers in the US may be directly related to obesity."
Dr. Chlebowski outlined several possible biochemical explanations to explain how obesity impacts cancer risk and cancer survival, including changes in how the body regulates insulin and other hormones.
"A recent study out of the University of Toronto found that the risk of developing a breast cancer recurrence increases exponentially as body mass increases," he said. Chlebowski believes that avoiding overweight and obesity may be one of the most direct and dramatic ways for a cancer patient to influence their risk of recurrence for the better.
Best, Science-Based Dietary Advice for Survivors
Dr. David Heber, Chair and co-founder of the Center for Human Nutrition at UCLA, concluded the conference by delineating practical, everyday steps that survivors can take that may help to reduce their risk of cancer. Variety and moderation are key, he said.
"The weight of evidence is convincing that a diet rich in a variety of vegetables, fruits, whole grains and beans helps reduce cancer risk among individuals who have never had cancer," he said. "There are no guarantees, of course. But these foods do contain potent vitamins, minerals and phytochemicals that seem to come to the body's aid to fight against and even halt the cancer process."
Although only a limited amount of research has specifically explored the role of diet among survivors, Dr. Heber and his colleagues at the conference believe it reasonable to assume that healthy dietary choices can significantly reduce the risk of recurrence and secondary cancers also.
"Eating a predominantly plant-based diet, drinking alcohol only in moderation or not at all, and avoiding tobacco completely - these are some of the simple, everyday steps that fortify the body's defenses. Such steps assume an even greater importance in the lives of survivors, whose systems may need a bit of extra help."
Nutrition and lifestyle inhibit the inflammation, oxidative damage and unregulated cell growth that are common mechanisms promoting the growth and spread of cancer, Heber said. And nutrition is one of the few things cancer patients and cancer survivors can control themselves.
"Many different plant foods provide health benefits, and the best way to take advantage of that fact is to eat a large variety. Loading up on any one food, or food substance, is never advisable," said Dr. Heber.
"There remains much - too much - we don't know about diet, nutrition and cancer recurrence," said Dr. Heber. "While we're waiting for more information, however, we do have some reliable, hard-won advice that will help to point our way."
AICR's Diet and Health Guidelines for Cancer Prevention
- Choose a diet rich in a variety of plant-based foods.
- Eat plenty of vegetables and fruits.
- Maintain a healthy weight and be physically active.
- Drink alcohol only in moderation, if at all.
- Select foods low in fat and salt.
- Prepare and store food safely.
- And always remember: Do not use tobacco in any form.
For more information, or to contact American Institute for Cancer Research, see their website at: www.aicr.org
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