Men Over Forty Should Not Consume Flaxseed Oil
Food/Nutrition November 19th, 2007Flaxseed has two components: the oil and the fiber. Recent research suggests that flaxseed oil’s main component–alpha linolenic acid–is associated with an increased risk to prostate cancer. To see this research firsthand, go to PubMed, and enter these search terms all at once: “alpha linolenic acid prostate” Flax has many benefits. The oil and the fiber are great for women of all ages. Flaxseed fiber contains lignans that have pronounced anti-cancer effects in both men and women–especially women. Flaxseed muffins have significant benefit for women with breast cancer according to recent research. Flaxseed fiber also appears to have benefits for men, especially those over 40. Yet flaxseed oil for these same men should be avoided. Why? We don’t know. But a good deal of research suggests it’s a problem, and until we have the answer, men over 40 should avoid flaxseed oil. Here’s the Harvard group’s study: and the most important sentence inthe abstract is:”Tomato sauce (inversely) and alpha-linolenic acid (positively)intakes were strong predictors of advanced cancer among those withlow-grade cancers at diagnosis.”One can’t ignore that. Here is the whole abstract:Int J Cancer. 2007 Oct 1;121(7):1571-8.Risk factors for prostate cancer incidence and progression in thehealth professionals follow-up study.Giovannucci E, Liu Y, Platz EA, Stampfer MJ, Willett WC.Channing Laboratory, Department of Medicine, Harvard Medical Schooland Brigham and Women’s Hospital, Boston, MA 02115, USA.edward.giovannucci@channing
was not. Onlyfor high calcium intake was there a close correspondence forassociations among high-grade cancer, advanced and fatal prostatecancer. Tomato sauce (inversely) and alpha-linolenic acid (positively)intakes were strong predictors of advanced cancer among those withlow-grade cancers at diagnosis. Although the proportion of advancedstage cancers was much lower after PSA screening began, risk factorsfor advanced stage prostate cancers were similar in the pre-PSA andPSA era. The complexity of the clinical and pathologic manifestationsof prostate cancer must be considered in the design and interpretationof studies.Here is another paper, and one that suggests that fish oils are better for men than flaxseed oil:Am J Clin Nutr. 2004 Jul;80(1):204-16.Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer.Leitzmann MF, Stampfer MJ, Michaud DS, Augustsson K, Colditz GC,Willett WC, Giovannucci EL.Nutritional Epidemiology Branch, Division of Cancer Epidemiology andGenetics, National Cancer Institute, National Institutes of Health,Department of Health and Human Services, Bethesda, MD 20892, USA.leitzmann@mail.nih.govBACKGROUND: Laboratory studies have shown that n-3 fatty acids inhibitand n-6 fatty acids stimulate prostate tumor growth, but whether thedietary intake of these fatty acids affects prostate cancer risk inhumans remains unclear. OBJECTIVE: We prospectively evaluated theassociation between intakes of alpha-linolenic (ALA; 18:3n-3),eicosapentaenoic (EPA; 20:5n-3), docosahexaenoic (DHA; 22:6n-3),linoleic (LA; 18:2n-6), and arachidonic (AA; 20:4n-6) acids andprostate cancer risk. DESIGN: A cohort of 47 866 US men aged 40-75 ywith no cancer history in 1986 was followed for 14 y. RESULTS: Duringfollow-up, 2965 new cases of total prostate cancer were ascertained,448 of which were advanced prostate cancer. ALA intake was unrelatedto the risk of total prostate cancer. In contrast, the multivariaterelative risks (RRs) of advanced prostate cancer from comparisons ofextreme quintiles of ALA from nonanimal sources and ALA from meat anddairy sources were 2.02 (95% CI: 1.35, 3.03) and 1.53 (0.88, 2.66),respectively. EPA and DHA intakes were related to lower prostatecancer risk. The multivariate RRs of total and advanced prostatecancer from comparisons of extreme quintiles of the combination of EPAand DHA were 0.89 (0.77, 1.04) and 0.74 (0.49, 1.08), respectively. LAand AA intakes were unrelated to the risk of prostate cancer. Themultivariate RR of advanced prostate cancer from a comparison ofextreme quintiles of the ratio of LA to ALA was 0.62 (0.45, 0.86).CONCLUSIONS: Increased dietary intakes of ALA may increase the risk ofadvanced prostate cancer. In contrast, EPA and DHA intakes may reducethe risk of total and advanced prostate cancer.And another paper:J Nutr. 2004 Apr;134(4):919-22.Dietary alpha-linolenic acid is associated with reduced risk of fatalcoronary heart disease, but increased prostate cancer risk: ameta-analysis.Brouwer IA, Katan MB, Zock PL.Wageningen Centre for Food Sciences, Wageningen, the Netherlands.ingeborg.brouwer@wur.nlThe objective of this meta-analysis was to estimate quantitatively theassociations between intake of alpha-linolenic acid [ALA, the (n-3)fatty acid in vegetable oils], mortality from heart disease, and theoccurrence of prostate cancer in observational studies. We identified5 prospective cohort studies that reported intake of ALA and mortalityfrom heart disease. We also reviewed data from 3 clinical trials onALA intake and heart disease. In addition, we identified 9 cohort andcase-control studies that reported on the association between ALAintake or blood levels and incidence or prevalence of prostate cancer.We combined risk estimates across studies using a random-effectsmodel. High ALA intake was associated with reduced risk of fatal heartdisease in prospective cohort studies (combined relative risk 0.79,95% CI 0.60-1.04). Three open-label trials also indicated that ALA mayprotect against heart disease. However, epidemiologic studies alsoshowed an increased risk of prostate cancer in men with a high intakeor blood level of ALA (combined relative risk 1.70; 95% CI 1.12-2.58).This meta-analysis shows that consumption of ALA might reduce heartdisease mortality. However, the association between high intake of ALAand prostate cancer is of concern and warrants further study.
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