Flaxseed slows prostate cancer – more evidence

Flax is a contentious issue among prostate cancer researchers. Dr. Dean Ornish on WebMed cites Dr. Charles "Snuffy" Myers' view of flaxseed oil as virtual fuel for prostate cancer tumors. Recommending omega-3 fatty acids in fish, Ornish notes some "disturbing research published by Dr. Charles 'Snuffy' Myers at the University of Virginia Medical School in Charlottesville. He has evidence indicating that flax seed oil may promote the growth of prostate tumors. In someone with prostate cancer, I would avoid flax seed oil and instead take 2-3 grams per day of fish oil."

Yet Wendy Demark-Wahnefried, Ph.D., a researcher in Duke's School of Nursing, continues to turn up evidence that flaxseed -- not flax oil -- inhibits growth of prostate cancer.

Flaxseed is an edible seed that is rich in omega 3-fatty acids and fiber-related compounds known as lignans. According to the latest study by Dr. Demark-Wahnefried, it is effective in halting prostate tumor growth. She and her team found that the seed, which is widely sold in food stores and supermarkets and included in specialty breads and cereals, may be able to interrupt the chain of events that leads cells to divide irregularly and become cancerous."Our previous studies in animals and in humans had shown a correlation between flaxseed supplementation and slowed tumor growth, but the participants in those studies had taken flaxseed in conjunction with a low-fat diet," Wendy Demark-Wahnefried said. "For this study, we demonstrated that it is flaxseed that primarily offers the protective benefit."

The researchers presented their results on Saturday, June 2, at the annual meeting of the American Society of Clinical Oncology, in Chicago. The multisite study, which was funded by the National Institutes of Health, also involved researchers at the University of Michigan and the University of North Carolina at Chapel Hill.

The researchers examined the effects of flaxseed supplementation on men who were scheduled to undergo prostatectomy -- surgery for the treatment of prostate cancer. The men took 30 grams of flaxseed daily for an average of 30 days prior to surgery. Once the men's tumors were removed, the researchers looked at tumor cells under a microscope, and were able to determine how quickly the cancer cells had multiplied.

Men taking flaxseed, either alone or in conjunction with a low-fat diet, were compared to men assigned to just a low-fat diet, as well as to men in a control group, who did not alter or supplement their daily diet. Men in both of the flaxseed groups had the slowest rate of tumor growth, Demark-Wahnefried said. Each group was made up of about 40 participants.

Study participants took the flaxseed in a ground form because flaxseed in its whole form has an undigestible seed coat, she said. Participants elected to mix it in drinks or sprinkle it on food, such as yogurt.

"The results showed that the men who took just flaxseed as well as those who took flaxseed combined with a low-fat diet did the best, indicating that it is the flaxseed which is making the difference," Demark-Wahnefried said.

Flaxseed is thought to play a part in halting the cellular activity that leads to cancer growth and spread. One reason could be that as a source of omega-3 fatty acids, flaxseed can alter how cancer cells lump together or cling to other body cells, both factors in how fast cancer cells proliferate, Demark-Wahnefried said. The researchers also suspect that lignans may have antiangiogenic properties, meaning they are able to choke off a tumor's blood supply, stunting its growth.

"We are excited that this study showed that flaxseed is safe and associated with a protective effect on prostate cancer," Demark-Wahnefried said. She says she and her teams hope to next test the effectiveness of flaxseed supplementation in patients with recurrent prostate cancer, and ultimately to study its role as a preventative agent.

The controversy over whether flaxseed consumption protects against prostate cancer or, on the contrary, stimulates its growth will likely continue until other research teams undertake and complete human studies to compare with those led by Dr. Demark-Wahnefreid.

Flaxseed oil is high in Alpha-linolenic acid (ALA) , which is the most common omega-3 fatty acid in the Western diet. In the passage Dr. Ornish cites, Dr. Myer's writes in his publication Prostate Forum:

In tissue culture and in animal studies, flax seed oil does possess impressive anticancer activity, including activity against prostate cancer. However, the impact on human cancer is very different. Nine published studies analyze the impact of alpha-linoleic acid on the risk of developing prostate cancer or on disease progression. Seven of these demonstrate a significantly increased risk of prostate cancer or cancer progression associated with the increased consumption of alpha-linolenic acid. One (Anderson, et al) showed no effect. There are no studies in the literature that document the benefit of flax seed oil in prostate cancer patients. A study by W. Demark-Wahnefried from Duke University reported a favorable impact of whole flax seed [not flax seed oil] on human prostate cancer. Infortunately, this study examined the combined impact of a low fat diet and flax seed on prostate cancer. Recent evidence suggests that a low fat diet alone can prevent the progression of prostate cancer; therefore, it’s possible that the beneficial results seen in Demark-Wahnefried's study had nothing to do with the flax seeds and were related to the low fat diet exclusively . . . . In sum, flaxseed oil poses a possible risk of prostate cancer progression and is an inefficient source of the required omega-3 fatty acids.

Dr. Myers urges men affected by prostate cancer to obtain DHA and EPAby from "ocean (not farm-raised) fish, fish oil capsules, or the algae-based supplement Neuromins instead of alpha-linolenic acid rich oils such as flax seed."

According to a a study researchers at National Institutes of health, "The relation of dietary intake of ALA to prostate cancer risk remains unresolved." In 2006, the NIH scientists prospectively evaluated total ALA and ALA from specific food sources including animal, fish, and plant sources in relation to prostate cancer risk. This was undertaken as part of the the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, which has produced some startling results including evidence that tomato and lycopene have no effect protective effect against prostate cancer.

The study of Alpha-linolenic acid (ALA) followed 29,592 male participants (age 55-74 years) for an average of 5.1 years. Among these men in this period 1,898 cases of total prostate cancer were diagnosed, of which 1,631 were organ-confined cases (stage T1b to T3a and N0M0) and 285 were advanced stage cases (stage>or=T3b, N1, or M1).

The researchers saw "no association between total ALA intake and overall prostate cancer . . . . In addition, no relations were observed between ALA intake from any specific food source and the risks of total, organ-confined, or advanced prostate cancer. ALA intake also showed no association with low grade (Gleason sum<7; 1,221 cases) tumors (P for trend=0.23) or high grade (Gleason sum>or=7; n=677 cases) tumors."

"In this prospective study of predominantly Caucasian men who were screened annually for newly incident prostate cancer," they write, "dietary intake of total ALA and ALA from specific food sources was not associated with risk of total prostate cancer or prostate tumors that were defined by stage and grade."

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