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Cancer: The Promising Potential of Omega-3s
8/15/2005
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Customer letter and new studies prompt a review of omega-3s’ broad anti-cancer benefits

by Craig Weatherby



Fiscal year 2006 will be one of the few in which federal cancer research funding will not increase.


Yet, according to the American Cancer Society, cancer now exceeds heart disease as the top cause of death among Americans under 85, with some 476,000 people dying from one form or another every year.  Close to half of all American men, and one-third of American women, will develop cancer.


The war on cancer: diet looms larger than ever

Given the limited control individuals can exert over environmental pollution and other societal risk factors, diet is looming ever larger as a factor that we can use to reduce the risk of cancer.


According to the author of a recent review of the scientific literature, published last year in the Journal of Nutrition, diet can play a big role in cancer prevention and treatment (sections underlined for emphasis):


“It has been estimated that 30-40 percent of all cancers can be prevented by lifestyle and dietary measures alone. Obesity … concentrated sugars and refined flour products… low fiber intake, consumption of red meat, and imbalance of omega 3 and omega 6 fats all contribute to excess cancer risk… abundant portions of fruits and vegetables will lower cancer risk.…


The author concluded his review with this encouraging estimate: “When a diet is compiled according to the guidelines here it is likely that there would be at least a 60-70 percent decrease in breast, colorectal, and prostate cancers, and even a 40-50 percent decrease in lung cancer, along with similar reductions in cancers at other sites. Such a diet would be conducive to preventing cancer and would favor recovery from cancer as well.”


Omega-3s: a promising cancer-fighter

Readers of our series on vitamin D may recall the comments by a Harvard researcher to the effect that the sunlight-generated vitamin—for which fish are the best dietary source—is unsurpassed as a natural anti-cancer agent.


However, a large body of research indicates that the long-chain omega-3s in fish and fish oil offer the nutrient serious competition with regard to prevention.


And, unlike vitamin D, marine omega-3s can also enhance the effectiveness of chemotherapies and radiation, and ease wasting symptoms.


We were prompted to put all the information in one place when we received this email message from Vital Choices reader P. Gilmore:  “I never see any special recipes for people with prostrate cancer or any other cancers. Surely there must be recommended foods for those on chemo or other therapies.”


So here it is, all in one place: an overview of the anti-cancer benefits of fish and fish oil, which summarizes all of our past articles on the subject, and adds some new information on omega-3s for breast cancer and omega-3s as an adjunct cancer therapy. This is sound information everyone should have... please forward it to all those you care about.


Omega-3s in cancer treatment

Since reader Gilmore’s letter prompted this review of the research on cancer and omega-3s, let’s start with their role in cancer treatment.


A review article published in the December, 2004 issue of the Journal of Nutrition supports the proposition that omega-3 fatty acids can offer an effective, non-toxic adjunct to toxic radiation and chemo therapies. According to the article’s authors, dietary omega-3 fatty acids perform three valuable functions:

  • Omega-3s can slow progression of cancers of the lung, colon, breast and prostate (animal studies).
  • Omega-3s can improve the efficacy of toxic cancer drugs such as doxorubicin, epirubicin, CPT-11, 5-fluorouracil, as well as the efficacy of tamoxifen and radiation therapy (animal studies).
  • Omega-3s—specifically, EPA—may improve the quality of life in people with cancer by combating cancer-associated appetite loss, physical wasting, and malnutrition.  We emphasize that omega-3s may help because the positive results of earlier studies of omega-3s in wasting were contradicted by more recent findings. The jury seems to be out on this aspect of adjunct therapy with omega-3s.

The available research results indicate that omega-3 fatty acids can constitute a credible alternative therapy for the minority of patients unable to withstand radiation or chemotherapy. It goes without saying that no one should attempt to fight cancer alone, without the guidance of an experienced oncologist.


General cancer-prevention power of omega-3s

The results of animal, test tube, and human population studies indicate strongly that omega-3s discourage certain cancers from starting: especially leukemia, and cancers of the breast, prostate, and uterine endometrial tissue.


Before we look at the evidence for individual cancers, we should start with an overview of why omega-3s help keep some common cancers from starting and growing.


Likely explanations for the benefits of dietary omega-3s include their ability to increase the propensity of cancer cells to undergo apoptosis (cellular “suicide”), modulation of estrogen signaling (i.e., reduce breast cancer promotion), and damping of the low-level inflammation known to initiate or accelerate the growth of common cancers, including prostate cancer.


In a metabolic sense, omega-3s pour cold water on the inflammatory fire underlying certain cancers.


As Andrew Weil, M.D. told an audience of physicians during his May, 2005 Nutrition & Health Conference at the University of Arizona, inflammation is now seen as key to promotion of many cancers:  “Classically, cancer has been considered as … separate from the degenerative conditions, but the same hormones that up-regulate inflammation also up-regulate cell division, and any time cell division increases, risk of malignancy is increased.”


It was once thought that omega-3s exert anti-inflammatory effects only by balancing pro-inflammatory metabolic factors—including the omega-6 fatty acid arachidonic acid—but we now know that omega-3s dampen inflammation in several distinct ways.


For example, recent in vitro (test tube) research shows that omega-3s alter expression of inflammatory genes.  Cell culture studies show that in particular, the marine omega-3 called EPA prevents activation of a nuclear transcription factor called NF?B.  This indicates that omega-3s reduce expression of inflammatory genes associated with cancer promotion.


This broad spectrum of anti-inflammatory effects explains why omega-3s may help prevent and ameliorate diseases with an inflammatory component, including diabetes, Alzheimer’s, cardiovascular disease, and many cancers.


As many researchers have said, it seems logical that a nutrient that slows cancer growth via proven physiological effects should also help reduce cancer risk.


Breast cancer: Singapore study supports preventive potential of omega-3s

The groundbreaking results of a study published in 2003 offer real hope of reducing breast cancer risk with dietary omega-3s.


Researchers at the University of Southern California and the National University of Singapore examined data from the Singapore Chinese Health Study to see whether there was any relationship between dietary fats and breast cancer risk.


After reviewing the dietary diaries and medical records of the 35,298 participating women, the researchers reported these encouraging findings: “…high levels of dietary n-3 fatty acids [omega-3s] from fish/shellfish (marine n-3 fatty acids) [EPA and DHA] were significantly associated with reduced risk.… To our knowledge, these are the first prospective findings linking the intake of marine n-3 fatty acids [omega-3s] to breast cancer protection.”


More specifically, the study showed that postmenopausal women who consumed an average of about 1.5 to 3 ounces of fish or shellfish daily were 30 percent less likely to develop breast cancer, compared with women who ate less than one ounce of seafood per day


Breast cancer: mouse study points up preventive value of maternal omega-3s

The results of two animal studies published in 2005 indicate that omega-3s are potent allies in the fight to prevent breast cancer.  And, the results of one of these investigations even indicates that pregnant and nursing women may reduce the chances of their daughters developing breast cancer by eating foods rich in omega-3s.


Researchers at Ohio State University tested the effects of omega-6 and omega-3 fatty acids on breast cancer in mice that had been given an anti-cancer drug. To their surprise, the drug (rosiglitazone) had no effect on mice bred to be prone to breast cancer, while the omega-3s had a dramatic positive effect.


As they reported, “…fish oil-based diets markedly suppressed breast tumor incidence (57% of mice vs. 87% of corn oil-fed mice) as well as tumor multiplicity… and mammary gland dysplasia… These findings demonstrate a potent preventive effect of [omega-3s] …”


In the second study, conducted at Louisiana State University, the risk of breast cancer in female mice varied greatly, depending on the type of fat that predominated in their mothers’ diet.


The mice in the LSU study were bred to have a genetic predisposition to breast cancer, and the mothers were fed diets high in either omega-6 fatty acids or omega-3 fatty acids, both during the gestation period and while breast-feeding their female young.


After weaning, one group of female offspring was placed on a high-omega-6 diet and the other was fed mostly omega-3.


The young mice exposed only to omega-6 fatty acids in utero, during nursing, and after weaning showed mammary gland tumors by six months of age.


In contrast, less than 60 percent of the offspring that ate a high omega-3 diet either in the womb or post-weaning had formed mammary tumors by the age of eight months.  Better yet, of the offspring that received omega-3s from the womb through to weaning, only 13 percent had developed tumors by the age of eight months.


The decreased incidence of cancer seen in the offspring of the mother mice placed on an omega-3-rich diet is likely linked to the fact that dietary omega-3s tend to decrease maternal estrogen levels.


Conversely, diets high in omega-6s increase maternal levels of estrogen: an effect linked to increased incidence of breast cancer in female offspring.


The author’s conclusion says it all: “Regular consumption of n-3 fatty acids may reduce risk of breast cancer. Increased consumption of n-3 fatty acids during pregnancy and lactation may be a viable dietary means for reducing the risk of breast cancer in the next generation.”


Unfortunately, omega-6 fatty acids are overabundant in the standard American diet, being found in foods like meat, eggs, poultry, cereals, breads, baked goods, vegetable oils, and margarine.


As study author Elaine Hardman, Ph.D. of LSU said in a press release, "Inadvertently, we may be setting up our daughters to develop breast cancer 50 years from now."


Prostate cancer

The results of a large, long-term study by researchers from the National Cancer Institute show that men who consume ample amounts of the fish-derived omega-3 fatty acids EPA and DHA have a reduced risk of prostate cancer. (Prostate cancer is second only to lung cancer as the most lethal cancer among men.)


This study authors examined 47,866 men between 40 and 75 years of age, who had no prostate cancer when the study began. After fourteen years, 2,965 men (six percent) had prostate cancer.


The men with the highest combined intake of EPA and DHA were 11 percent less likely to develop prostate cancer and 26 percent less likely to develop advanced prostate cancer.


And, the study also showed that eating too much LA—the omega-6 fatty acid that is overabundant in most diets, thanks to its prominence in cooking oils and processed foods—may increase the risk of being diagnosed with advanced prostate cancer.


Surprisingly, given the bad reputation of red meats, the researchers found that eating too much omega-3 ALA from plant sources (vegetable oils, nuts, seeds, etc.) increased the risk of advanced prostate cancer twice as much (100 percent increase in risk) as eating too much ALA from meat and dairy sources (50 percent increase in risk).


Leukemia and other blood-cell cancers

In 2004, Canadian researchers published their analysis of a previous population study, and found data suggesting that omega-3s may help prevent several cancers affecting white blood cells, including leukemia, multiple myeloma, and non-Hodgkin lymphoma.


The results indicated that the respondents who ate fish most often and derived the highest percentages of their total energy or fat from fish were significantly less likely to have one of these cancers of the blood.


Between 1994 and 1998, researchers from the Canadian Cancer Registries Epidemiology Research Group examined the responses of 2,624 people with one of these white blood cell cancers who’d been asked about their diet.  The scientist also examined the responses from 4,200 healthy "controls" who’d taken the survey.


Interestingly, an earlier study based on the same interview found that people in occupations associated with beef cattle—a source of omega-6 fatty acids associated with increased cancer risk—suffer an increased risk for developing leukemia and lymphoma, while workers who handle fish on the job had a decreased risk of leukemia and lymphoma.


In conclusion: a plea for prevention
In spite of the billions of dollars spent annually to beat cancer, statistics indicate that, with the exception of certain cancers, we are making little headway.  Perhaps the problem is that most of this money is spent trying to cure cancer, when more of it should be directed toward figuring out how we can avoid it in the first place.  
 
The encouraging results of a fast-growing body of research suggest that sound dietary choices offer a potent defense against this menacing, life-destroying adversary.



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