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Flaxseed or linseed (Linum usitatissimum) is a product of the flax plant, an annual herb that is high in fiber and a substance called mucilage. Together these components have made flaxseed an effective laxative, a use for which it has been valued for millennia.
How Flaxseed Works
Flaxseed and flaxseed oil are also rich in an omega-3 fatty acid called alpha-linolenic acid (ALA), which has demonstrated health benefits regarding prostate cancer, benign prostatic hyperplasia, heart disease, high cholesterol, inflammatory bowel disease, arthritis, and other health problems. However, not all the studies for each of these conditions have been positive. For treatment of high blood pressure and reducing elevated blood sugar levels in people who have diabetes, the evidence has been convincing, and these benefits have been attributed to flaxseed’s high soluble fiber content. In the area of prostate health and prostate cancer in particular, the findings have been mixed.
Studies of Flaxseed and Flaxseed Oil
In a pilot study conducted at Duke University Medical Center, researchers explored the impact of a flaxseed-supplemented, low-fat diet on the proliferation rates in benign prostate epithelium. Fifteen men who were scheduled to undergo prostate biopsy were placed on a low-fat, flaxseed-supplemented (30 g daily) diet for six months. Investigators observed a statistically significant decrease in the benign epithelium, as well as in PSA and cholesterol levels when compared with the men’s baseline levels. The authors of the study suggested that a flaxseed-supplemented, low-fat diet may have a positive impact on controlling prostate growth. (Demark-Wahnefried 2004)
Researchers have found flaxseed to be effective in the fight against prostate cancer as well. In a controlled trial conducted at The University of Texas MD Anderson Cancer Center, investigators evaluated the impact of flaxseed supplementation and/or a low-fat diet on 161 men with prostate cancer who were scheduled for prostatectomy. For an average of 30 days before surgery, the men participated in one of four groups: control (usual diet), flaxseed supplemented diet (30 g per day), low-fat diet, or a flaxseed-supplemented, low-fat diet. When the researchers examined the tumors removed from the men during prostatectomy, they found that proliferation of prostate cancer growth was significantly lower in the men in both of the groups that included flaxseed. (Demark-Wahnefried 2008)
According to lead author Wendy Demark-Wahnefried, the omega-3 fatty acids in flaxseed appear to change how cancer cells lump together or bind to other cells, while the lignans (a phytonutrient/phytoestrogen) in flaxseed choke off the blood supply to the tumor, which helps stop cancer’s growth.
Other studies have challenged the claims that flaxseed is beneficial for prostate health. In a large review of available literature on flaxseed in humans, experts from Memorial Sloan-Kettering Cancer Center identified 13 categories in which flaxseed had been studied. The categories included prostate cancer, constipation, attention-deficit hyperactivity disorder, high cholesterol, atherosclerosis, breast cancer, cyclic breast pain, menopausal symptoms, diabetes, high blood pressure, lupus nephritis, and HIV/AIDS. Their conclusion was that nearly all the studies had been of poor quality and that “although flaxseed and flaxseed oil have several promising future uses, the available literature does not support recommendation for any condition at this time.” (Basch 2007)
One of the studies reviewed was published in the American Journal of Clinical Nutrition, and reported on work by researchers who explored the association between the risk of prostate cancer and intake of the omega-3s—ALA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)—and the omega-6 fatty acids linoleic acid and arachidonic acid. A total of 47,866 men were followed for 14 years.
The investigators identified 2,965 new cases of total prostate cancer during the follow-up period, and 448 of these cases were advanced. When the men’s intake of omega-3 and omega-6 fatty acids was analyzed, it was discovered that intake of ALA was associated with an increased risk of advanced prostate cancer, and that ALA from nonanimal sources such as flaxseed and flaxseed oil provided a greater risk than ALA from meat and dairy sources. Intake of EPA and DHA, however, was associated with a lower risk of prostate cancer, both total and advanced, and the omega-6 fatty acids were unrelated to prostate cancer risk. (Leitzmann 2004)
How To Take Flaxseed
Generally, the suggested amount of flaxseed to take daily is 1 tablespoonful, 2 to 3 times daily, or 2 to 4 tablespoons once daily. (University of Maryland) The seeds should be ground before they are consumed, as this improves their digestibility, and you should take them with a full glass of water. The ground flaxseeds can also be added to foods, such as oatmeal, salads, and smoothies.
Side Effects of Flaxseed
Possible side effects of flaxseed (ground or whole) include gas, heartburn, indigestion, and nausea. Flaxseed oil in large amounts may cause flatulence and loose stools.
References
Basch E et al. Flax and flaxseed oil (Linum usitatissimum): a review by the Natural Standard Research Collaboration. J Soc Integr Oncol 2007 Summer; 5(3): 92-105
Demark-Wahnefried W et al. Pilot study to explore effects of low-fat, flaxseed-supplemented diet on proliferation of benign prostatic epithelium and prostate-specific antigen. Urology 2004 May; 63(5): 900-4
Demark-Wahnefried W et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiol Biomarkers Prev 2008 Dec; 17(12): 3577-87
Leitzmann MF et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr 2004 Jul; 80(1): 204-16
University of Maryland Medical Center: http://www.umm.edu/altmed/articles/flaxseed-000244.htm
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