Originally published 3/14/2016
Judging by the relative scarcity of recent research papers on flaxseed, it seems that after some initial enthusiasm in the first decade and a half of the new millennium, interest in flaxseed has faded. Along with the Duke University study described in the blog below, several studies have shown an anti-prostate cancer benefit from dietary flaxseed. However, according to an Oncology Nutrition article, “Current observational research does not support that dietary flaxseeds can reduce the risk of developing prostate cancer.” While the American Institute for Cancer Research (AICR) lists the beneficial compounds in flaxseed known to have anti-inflammatory and anti-cancer properties, it advises, “Flaxseed’s potential influence on breast, prostate, and other hormone-related cancers has led to an interest in its role for the prevention and survivorship of these cancers. Results have shown mixed findings, and much more human research is needed.”
Though we were unable to find new human research, we discovered a 2018 report of an animal experiment involving exposure to tobacco smoke carcinogen (cancer-causing NNK) and the risk of lung cancer in mice.[i] Mice exposed to NNK were fed either a control diet or a 10% flaxseed-supplemented diet for 26 weeks. The mice on the flaxseed supplements had 78% less incidence of lung tumors and a lower incidence of adenocarcinomas than controls (prostate cancer is one type of adenocarcinoma). Based on pathology and genomic analysis, the authors theorized that flaxseed offered cancer protection by altering signaling pathways, reducing inflammation, and causing less oxidative stress. We support the AICR’s position that more human research is in order.
Many of my patients are very nutrition-conscious in terms of overall wellness. I have previously written about the benefits of heart-friendly diets because they also support prostate health (see https://sperlingprostatecenter.com/heart-healthy-choices-promote-prostate-health/). The basics of healthy eating include less red meat (more chicken and fish if you’re a carnivore), more fruits and vegetables (preferably organic), nuts, whole grains, less sugar, fat and alcohol, and plenty of antioxidants.
Recently, flaxseed has started gaining attention for the numerous benefits it offers. These include
- Dietary fiber
- High in antioxidants (help prevent heart disease)
- High omega-3 fatty acid content
- May help control blood pressure
- May help reduce the proportion of “bad cholesterol”
- High in plant lignans which may help prevent prostate cancer (PCa) from spreading
You are probably thinking, “Plant lignans? What are those and what do they have to do with PCa?” Lignans are chemicals found in plants. They are called phytoestrogens because their molecular structure is similar to the female hormone estrogen, so the connection with hormone driven breast and prostate cancer is of great interest to researchers. Lignans are found cereal grains (especially rye), cruciferous vegetables, apricots, berries, and sesame seed. However, flaxseed tops the list of foods rich in lignans.
A 2013 study from Duke University reported an excellent analysis of flaxseed supplements and the role they might play in controlling tumor cell growth by inhibiting PCa’s ability to build a new blood supply (angiogenesis).[ii] When flaxseed is consumed, certain substances called enterolignans that are known to inhibit tumor growth are released into the bloodstream. Eventually, higher levels of these substances show up in urine where they can be measured. The research team recruited 161 men scheduled for prostatectomy. For about 30 days before their surgery, they were randomly assigned to one of 3 groups:
- Group A (flaxseed group) consumed 30 grams/day of whole-ground flaxseed with or without a low fat diet
- Group B (low fat group) consumed less than 20% of daily calories from fat
- Group C (control group) made no dietary changes
For purposes of the study, the team took pre and post urine samples to measure changes in the enterolignan concentrations. At baseline, all groups had basically equal concentrations, but at the end of the study group, those who consumed flaxseed had much higher lignan levels. The research group also had access to tumor markers from the prostate specimens of 147 patients. They found that the men with the highest enterolignan concentrations (i.e. those who consumed flaxseed) had the lowest expression of genes that promote tumor growth. This is called an inverse proportion, in other words, the more of A, the less of B. In short, the patients who used flaxseed had reduced risk of prostate cancer proliferation. Depending on the biomarker, the risk reduction ranged from modest to moderate to significant.
There are cautions about suddenly adding flaxseed to your diet. The best form is organic ground flaxseed, which can be sprinkled into soups, salads, pasta, etc. It can also be baked into muffins or other baked goods. Ease into it, as the additional fiber can cause intestinal irritation leading to diarrhea, so it’s best to add it gradually. It may not be wise to go as high as 30 grams/day, since that amount was for clinical observation over a 30 day pre-surgery period. Most people who supplement with flaxseed take 1-2 tablespoons per day (about 7-14 grams), and gradually work up to that.
Avoid flaxseed oil. The oil does not contain the lignans, and because it’s pure fat, it may do more harm than good if you’re striving to reduce fat in your diet (except for healthy fats).
One last note: A member of the Duke U. research team, Dr. Thomas Polascik, has long been interested in focal therapy for PCa. I personally find the flaxseed research valuable in connection with our focal laser ablation (FLA) at the Sperling Prostate Center. As with all advances in understanding the relationship between what we put in our bodies and prostate cancer, there are particular implications for flaxseed supplementation and controlling the spread of prostate cancer. If you are considering focal therapy, talk to your own doctor or nutritional consultant on the merits of adding flaxseed to your nutrition.
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[i] Chikara S, Mamidi S, Sreedasyam A, Chittem K et al. Flaxseed Consumption Inhibits Chemically-induced Lung Tumorigenesis and Modulates Expression of Phase II Enzymes and Inflammatory Cytokines in A/J Mice. Cancer Prev Res (Phila). 2018 Jan; 11(1): 27–37.
[ii] Azrad M, Vollmer RT, Madden J, Dewhirst M et al. Flaxseed-derived enterolactone is inversely associated with tumor cell proliferation in men with localized prostate cancer. J Med Food. 2013 Apr; 16(4): 357–360.
About Dr. Dan Sperling
Dan Sperling, MD, DABR, is a board certified radiologist who is globally recognized as a leader in multiparametric MRI for the detection and diagnosis of a range of disease conditions. As Medical Director of the Sperling Prostate Center, Sperling Medical Group and Sperling Neurosurgery Associates, he and his team are on the leading edge of significant change in medical practice. He is the co-author of the new patient book Redefining Prostate Cancer, and is a contributing author on over 25 published studies. For more information, contact the Sperling Prostate Center.
