As reviewed in the journal Microbiology Spectrum on December 7, 2023, researchers reminded us of previous studies showing that postmenopausal women with high blood levels of lignans have reduced risk of breast cancer mortality. Women with the highest blood and urinary levels of lignans are generally women who regularly consume ground flaxseed, as flaxseeds are the richest source of these important protective phytonutrients.  More accurately,  flaxseed contains the precursor to these phytonutrients, known as enterolactone and enterodiol. When ground flaxseed enters the large intestine our gut bacteria metabolize these precursor (known as SDG – secoisolariciresinol diglucoside) into enterolactone and enterodiol, which are then absorbed into the bloodstream. After circulating to breast cells, enterolactone and enterodiol have been shown to exert anti-cancer effects, such as slowing down the rate of cell division and prompting cell death of emerging breast cancer cells (apoptosis).

In the December 7, 2023. issue of the Microbiology Spectrum journal researchers published data to show new mechanisms by which ground flaxseeds may help to reduce risk of breast cancer in women. In recent years researchers have discovered that microRNA (mi RNA) within our cells act as epigenetic switches that “turn on and off “certain genes. The “switching off” of certain genes in breast cells is emerging as a critical way to help reduce breast cancer and researchers have identified the mi RNA types that are now well established as biomarkers for increased risk of breast cancer and which mi RNA types are associated with decreased risk of breast cancer.

With this understanding these researchers used a murine model (mouse model) to show that feeding female mice ground flaxseed reduced the mi RNA forms that are linked to increased breast cancer, and it increased the mi RNA forms that are linked to decreased breast cancer. Mice fed the basal diet without ground flaxseed did not show this protective effect. More specifically, in the mice provided with ground flaxseed, they showed higher ground flaxseed metabolites in the blood and higher amounts of mi RNA that help protect against breast cancer, which are mi RNA-137 and mi RNA-340-5p.  These two micro-RNA’s “switch off” two important genes (Runx2 and Skp2) that in turn reduce the activity of key signalling pathways in breast cancer development and progression (PI3K-Akt-mTOR pathway).  Switching off the Runs2 gene also reduces the ability of breast cancer stem cells to regenerate. Evidence suggests that many cancers, including breast cancers, arise from breast stem cells. Inhibiting their ability to regenerate helps to mitigate breast cancer risk and breast cancer progression.

A consistent finding in human breast cancer studies is that the Runx2 and Skp2 gene expression is increased and levels of mi RNA -137 and mi RNA-340 are decreased. Consuming ground flaxseed is shown to reverse both risk factors. For many years I have suggested that women should consume 2 heaping tablespoons of ground flaxseed each day to help reduce risk of reproductive organ cancers. And with each decade that passes the evidence grows stronger that consuming ground flaxseed provides a heightened level of protection against breast cancer. The 2023 study in the journal Microbiology Spectrum has shown new mechanisms through which ground flaxseed may be protective, which involves important epigenetic influences over key genes that are intimately involved in breast cancer development. Similar findings apply to men with respect to risk of prostate cancer, as ground flaxseed consumption also slows down the rate of prostate cell division – an important aspect of preventing prostate enlargement and prostate cancer.

So, my recommendation remains the same. Most adults should consider ingesting 2 tablespoons of ground flaxseed daily to derive the multitude of benefits available from this intervention, as constituents in flaxseed also helps to keep cholesterol down and improve intestinal function in addition to their protective effects on our reproductive organs. I have provided the references for this information in the text below.

References:

Wu H et al. Cecal microbiota and mammary gland microRNA signatures are related and modifiable by dietary flaxseed with implications for breast cancer risk. ASM Journal/Microbiology Spectrum. December 7, 2023. https://journals.asm.org/doi/10.1128/spectrum.02290-23

Denmark-Wahnefried et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiology Biomarkers and Prevention J. 2008; 17(12): 3577-87. https://pubmed.ncbi.nlm.nih.gov/19064574/

Eat Smart, Live Well, Look Great,
Dr. Meschino