Check out this answer from Consensus:
While the evidence from animal studies and some clinical trials is promising, more extensive and well-designed clinical trials are needed to establish the efficacy of flaxseed in preventing breast cancer. Nonetheless, the current findings suggest that flaxseed, due to its rich composition of beneficial compounds, holds potential as a complementary approach in breast cancer prevention and treatment.
Breast cancer remains one of the most prevalent cancers affecting women globally. With increasing interest in dietary interventions for cancer prevention, flaxseed has garnered attention due to its rich composition of omega-3 fatty acids, lignans, and fibers. This article explores the potential of flaxseed in preventing breast cancer, drawing on findings from various research studies.
Mechanisms of Action
MiRNA Modulation
Flaxseed and its components, such as flaxseed oil (FSO) and secoisolariciresinol diglucoside (SDG), have been shown to influence the miRNA signature in the mammary gland. These diet-specific miRNA signatures are associated with breast cancer and target genes involved in mammary gland development and cancer1. This suggests that early-life exposure to flaxseed could potentially reduce breast cancer risk by modulating miRNA expression.
Tumor Biomarkers
Clinical trials have demonstrated that dietary flaxseed can alter tumor biological markers. For instance, a study involving postmenopausal breast cancer patients showed significant reductions in tumor cell proliferation, c-erbB2 expression, and increased apoptosis in the flaxseed group compared to the placebo group2. These findings indicate that flaxseed may have a direct impact on tumor growth and progression.
Growth Factor Pathways
Flaxseed oil has been found to reduce the growth of estrogen receptor-positive human breast tumors by downregulating growth factor-mediated pathways. This includes the reduction of human epidermal growth factor receptor-2 (HER2) and epidermal growth factor receptor (EGFR) expression, which are critical in breast cancer development3. Additionally, flaxseed has been shown to inhibit the expression of insulin-like growth factor I (IGF-I) and EGFR, further supporting its role in reducing tumor growth and metastasis6.
Clinical Evidence
Systematic Reviews and Meta-Analyses
A systematic review of randomized controlled trials (RCTs) highlighted the potential benefits of flaxseed in breast cancer prevention. While some studies showed significant reductions in tumor biomarkers, others did not find any significant differences. The review concluded that current clinical research is too limited to make definitive recommendations but suggested that flaxseed appears to be safe with mild side effects4.
Animal Studies
Animal studies have provided substantial evidence supporting the anticancer properties of flaxseed. For example, flaxseed combined with tamoxifen significantly reduced tumor size in estrogen-dependent breast cancer models7. Another study demonstrated that flaxseed oil enhanced the effectiveness of trastuzumab in reducing the growth of HER2-overexpressing tumors8.
Potential Benefits and Safety
Antioxidant and Anti-inflammatory Properties
Flaxseed’s components, such as alpha-linolenic acid (ALA) and lignans, possess antioxidant and anti-inflammatory properties. These properties contribute to its potential in reducing cancer risk and mitigating the side effects of conventional cancer treatments10.
Apoptosis Induction
In vitro studies have shown that flaxseed extract can induce apoptosis in human breast cancer cells, suggesting its potential as a dietary supplement for cancer prevention9.
Can flaxseed prevent breast cancer?
Giovanni Colonna has answered Likely
An expert from University of Campania Luigi Vanvitelli in Biochemistry, Molecular Biology, Bioinformatics, Breast Cancer
Cancer is a proteiform disease. It continually changes the characteristics of its cells and in different individuals the same type of cancer can develop metastases with different cell characteristics. This often makes certain drugs useless. With very few exceptions, cancer is not yet curable because there is no cure. Only today is a window opening, but many drugs still allow only survival for a period, whose duration depends on many individual variables and always with high costs and unpleasant side effects. Therefore, the most powerful weapon we possess remains prevention, in all its forms. The fundamental reason for such a delay is the lack of knowledge that we still have today of cancer biology, of the structural organization of chromatin, and of the molecular and informational mechanisms involved, because cancer is an essentially informational disease
These facts have pushed the research to highlight the possible preventive (or curative) effects of substances contained in particular foods, commonly from the plant world. In many cases there are in vitro antitumor potentialities that are not always confirmed in vivo. All this feeds an extremely rich and flourishing world market of food supplements.
Flaxseed is one of the foods studied for its possible relations to breast cancer. As usual, we have mainly studies in animals and cell models, but still few clinical trials, moreover some studies are controversial.
Flaxseeds must be ground to improve the bioavailability of its nutrients, and they are considered a functional food containing nutrients with specific properties. In fact, in these seeds we find good amounts of α-linolenic acid and fibers, while they are very rich in omega-3 fatty acids and lignans, where the content of lignans is one of the most abundant. Also, flaxseeds are a source of zinc, magnesium, selenium, manganese, and vitamin B1.
The presence of omega-3 fatty acids seems associated to the reduction of breast cancer risk. Furthermore, some studies in animals show that α-linolenic acids is able to suppress growth and proliferation of breast cancer cells and also to promote the death of these cells.
Also lignans seem to play a role in cancer. They are digested and made bioavailable by the bacteria of the intestinal biome. In fact, some metabolic derivatives of lignans have shown antiestrogen activity because they are structurally similar to the human estrogen, thus, they can mimic the physiological hormone binding to specific cellular receptors, and, as a consequence, the cell growth decreases. For these reasons the lignans are considered phytoestrogens and can relieve the symptoms of menopause, balancing the effects of the physiological hormone.
Although many studies report that flaxseed intake may be related to the decreased risk of breast cancer and researchers have observed the potentiality of this food in reducing the growth of tumor in patients with breast cancer, mainly postmenopausal women, further clinical studies are needed to demonstrate benefits of the flaxseeds. Being cautious is a must, therefore at moment we must declare as potential the effects of flax seeds for the treatment of this cancer. We have yet to figure out which of the metabolites has a real action in vivo against cancer, how to isolate it, how to make it bioavailable and what are its side effects. However, inserting flax seeds into the diet certainly brings other beneficial effects due to the presence of omega 3 and to ability of fibers to reduce constipation.
Can flaxseed prevent breast cancer?
Michael Donaldson has answered Likely
An expert from Hallelujah Acres Foundation in Nutrition
Flaxseed is has been shown to reduce breast cancer risk in women, so it can be used to help prevent breast cancer. It is not a silver bullet treatment, but can be used as part of an overall comprehensive nutritional program to optimize health.
An abstract from a recent paper summarizes the evidence better than I can, so I will quote it here, putting it into layman’s terms as much as possible. See https://www.ncbi.nlm.nih.gov/pubmed/24869971 for the original text.
Flaxseed (FS), rich in the phytoestrogen lignans and α-linolenic acid-rich oil, has been suggested to have an anticancer effect. People still aren’t sure whether flaxseed or its lignan can help prevent breast cancer. Is flax seed safe to use after having breast cancer? To find answers we reviewed basic research as well as observational and clinical studies in women. The majority of studies in various rodent models show that 2.5%-10% FS diet or the equivalent amount of lignan or oil reduces tumour growth. In animal studies 10% FS and equivalent lignans not only don’t interfere with treatment but increase the effectiveness of tamoxifen (80 mg/day) while the 4% FS oil increases trastuzumab/Herceptin (2.5 mg/kg) effectiveness. Observational studies in women show that FS and lignan intake, urinary excretion, or serum levels are associated with reduced risk of breast cancer, particularly in postmenopausal women. Lignans reduce breast cancer and all-cause mortality by 33%-70% and 40%-53%, respectively, without reducing tamoxifen effectiveness. Short clinical trials show that FS (25 g/day with 50 mg lignans; 32 days) reduces tumour growth in breast cancer patients and lignans (50 mg/day; 1 year) reduces risk in premenopausal women. Mechanisms for reducing breast cancer risk include making breast cancer cells grow slower, reducing the growth of new blood supplies to the tumor and increased programmed cell death of tumor cells. This happens through normalizing estrogen metabolism and estrogen receptor and growth factor receptor signalling pathways. While more clinical trials are always needed, the current overall evidence indicates that FS and its components are effective in the risk reduction and treatment of breast cancer and safe for consumption by breast cancer patients.
Can flaxseed prevent breast cancer?
David Ma has answered Likely
An expert from University of Guelph in Nutrition
There is a body of research that supports the benefits of flax (whole and components) for breast cancer prevention in experimental (animal) and to a lesser degree humans. As mentioned by other experts, flax is not a magic bullet. Nutrition should be viewed as providing a supportive role in health just like building a house. If you build a house with high quality materials (like food and nutrients) you will have a house that lasts a long time.
One of the leading experts that has studied flax for breast cancer prevention is Dr. Thompson at the University of Toronto. Dr. Thompson has previousy conducted human research on flax and breast cancer https://www.ncbi.nlm.nih.gov/pubmed/15897583
Recently, our group has shown in experimental models that flax containing omega-3 fatty acids (alpha linolenic acid) is protective for breast cancer. In addition, we provide evidence for its relative effects in comparison to omega-3 (EPA/DHA) found in marine foods. Both are beneficial but omega-3s found in fish and seafood are 8-times more potent. Omega-3’s from plant sources including flax should be viewed like a mutual fund providing consistent benefit, which is a major source of omega-3s in the North American diet. https://www.ncbi.nlm.nih.gov/pubmed/29413488