Should Men Take Flax Seeds to Lower the Risk of Prostate Cancer: Find Out What the Latest Medical Research Has To Say
Medical Studies Show Mixed Results
On October 25, 2007, a urologist writing in the Mayo Clinic’s online “Ask a Prostate Cancer Specialist” column said, “Overall, it remains unclear whether flaxseed or flaxseed oil has a role in the prevention or treatment of prostate cancer. Until more definitive studies are available, it’s probably best for men to avoid supplementation with high doses of flaxseed.” [Source: https://www.mayoclinic.com/health/flaxseed/AN01712
News Reports vs. Medical Newsletters
Adding to the confusion are popular newspaper reports that seize upon one study or findings of a “nutritional scientist” and run headlines like this one: “Whole flax seed not tied to higher cancer risk.” [Source: San Diego Union-Tribune, May 3, 2006.] In contrast, one of the most respected doctors and researchers on prostate cancer, Dr. Charles Myers, M.D., in his newsletter dated April 15, 2008, wrote, “A bulk of the evidence suggests that flaxseed oil may speed progression of prostate cancer. . . . human males largely lack the capacity to metabolize the omega 3 fatty acids found in flax to EPA and DHA, the omega 3 fatty acids that are generally regarded as responsible for suppressing cancer progression. Flaxseed represents a different problem. While it contains flaxseed oil, it also contains a range of other interesting compounds.” Differences between flax seed oil and flax seeds containing flax oil complicate the issue.
Some Research Suggests Flax Seeds May Prevent Prostate Cancer
Several important reports showing positive benefits for prostate cancer prevention are found in the medical literature. A clinical study on the topic was completed in 2006 but full results are not yet available to the general public. The principal investigator on the study was Wendy Demark-Wahnefried, Ph.D., with the Division of Urologic Surgery, Duke University Medical Center, Durham, NC. In a published article, Dr. Demark-Wahnefried reports on a pilot study exploring the effects of a low-fat, flax seed supplemented diet on benign prostatic epithelium and circulating PSA levels. She says, “Statistically significant decreases in PSA (8.47 +/- 3.82 to 5.72 +/- 3.16 ng/m and cholesterol 241.1 +/- 30.8 to 213.3 +/- 51.2 mg/dL) were observed.” Also, in thirteen men who underwent follow-up biopsy, “the proliferation rates in the benign epithelium decreased significantly from 0.022 +/- 0.027 at baseline to 0.007 +/- 0.014 at 6 months of follow-up.”
Her conclusion is important: “A randomized, controlled trial is needed to determine whether flaxseed supplementation, a low-fat diet, or a combination of the two regimens may be of use in controlling overall prostatic growth. While this study indicates positive results as far as prostatic epithelium proliferation rates (perhaps a beneficial effect on benign prostatic hyperplasia, it really says nothing significant about prostate cancer itself other than the lowering of PSA levels, which can be affected by prostate size itself. [Source: W. Demark-Wahnefried, et al., “Pilot study to explore effects of low-fat, flaxseed-supplemented diet on proliferation of benign prostatic epithelium and prostate-specific antigen,” [Source: Urology 63:5 (May 2004), 900-904.]
An earlier study by Demark-Wahnefried reported on dietary flax restriction and flax seed supplementation in men with prostate cancer before surgery. Total cholesterol decreased for men on the diet, while PSA levels went up slightly for the whole sample (baseline: 8.1 +/- 5.2 ng/mL and end of study: 8.5 +/- 7.7 ng/mL). However, for patients with Gleason sums of six or less, the PSA went down (7.1 +/- 3.9 ng/mL and 6.4 +/- 4.1 ng/mL). [Source: Demark-Wahnefried, et al., “Pilot study of dietary fat restriction and flaxseed supplementation in men with prostate cancer before surgery: exploring the effects on hormonal levels, prostate-specific antigen, and histopathologic features,” Urology 58:1 (July 2001), 47-52.] The problem with both these studies is knowing whether beneficial results came from low-fat restrictions or flax seeds or both. This particular scientist has been working on the question since the mid-1990s and from other comments does seem convinced that a combination of the two elements will lower prostate cancer proliferation rates
Other Research Suggests Flax Seeds May Increase Prostate Cancer Risk
One study that may have launched the concern about flax seeds and prostate cancer took place in Uruguay from 1994 to 1998. This was a case-control study on diet and prostate cancer to look at the relationship between fat intake and cancer. 217 men with advanced prostate cancer were matched with 431 controls based on age, residence, and urban/rural status. “Five of six studies that have examined the relationship between alpha-linolenic acid and prostate cancer yielded a positive association, which was significant in four studies. Thus, there appears to be evidence of a role of alpha-linolenic acid in prostate carcinogenesis.” [Source: E De Stéfani, et al., Alpha-linolenic acid and risk of prostate cancer: a case-control study in Uruguay,” Cancer, Epidemiology, Biomarkers Prevention 9:3 (March 2000), 335-338.]
A meta-analysis of five cohort studies, three clinical trials and nine case-control studies looked at alpha-linolenic acid intake, heart disease mortality, and prostate cancer. While high ALA intake was correlated with a reduced risk of fatal heart disease, there was “an increased risk of prostate cancer with high intake or blood level of ALA.” [Source: I.A. Brouwer, “Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis,” The Journal of Nutrition 134:12 (December 2004), 3385.]
Are Any Conclusions Possible?
At this point, given the mixed results from even very recent studies, it does not seem possible to make a definitive decision on whether men should use flax seeds as a health supplement. Many experts do seem to agree the beneficial results from fatty-acids (ALA, EPA and **DHA) `**can come equally well from fish oil. Flax oil by itself seems to get more negative reviews as far as prostate cancer risks or exacerbations. Flax seeds have mixed reports, although the positive ones do appear to couple the effects of ALA and low-fat diets. Also, there may be differences in the value of flax seeds between men who do not have prostate cancer and those who have been treated for the disease.
What should the health conscious man conclude? This article is certainly not the place to promulgate recommendations. Only medical doctors, particularly those who are actively studying the disease, can give a patient advice. At most, reading the above research and other materials, it might be said that if one is going to supplement with flax seeds, then the whole/ground seeds would be preferable to flax oil. Furthermore, the use of flax seeds might be safer when combined with a low-fat diet in general.
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