The Effect of Flaxseed in Breast Cancer: A Literature Review

Abstract

Breast cancer is one of the most common cancers and the second most responsible for cancer mortality worldwide. In 2014, in Portugal approximately 27,200 people died of cancer, of which 1,791 were women with breast cancer. Flaxseed has been one of the most studied foods, regarding possible relations to breast cancer, though mainly in experimental studies in animals, yet in few clinical trials. It is rich in omega-3 fatty acids, α-linolenic acid, lignan, and fibers. One of the main components of flaxseed is the lignans, of which 95% are made of the predominant secoisolariciresinol diglucoside (SDG). SDG is converted into enterolactone and enterodiol, both with antiestrogen activity and structurally similar to estrogen; they can bind to cell receptors, decreasing cell growth. Some studies have shown that the intake of omega-3 fatty acids is related to the reduction of breast cancer risk. In animal studies, α-linolenic acids have been shown to be able to suppress growth, size, and proliferation of cancer cells and also to promote breast cancer cell death. Other animal studies found that the intake of flaxseed combined with tamoxifen can reduce tumor size to a greater extent than taking tamoxifen alone. Additionally, some clinical trials showed that flaxseed can have an important role in decreasing breast cancer risk, mainly in postmenopausal women. Further studies are needed, specifically clinical trials that may demonstrate the potential benefits of flaxseed in breast cancer.

Complementary and Alternative Medicine (CAM) Usage in Breast Cancer

“…Flaxseed possesses anti-estrogen activity, and its chemical component is able to bind to cell receptors resulting in a decrease in the cell growth. Certain studies have demonstrated that flaxseed may have an important role in decreasing the risk of breast cancer [39]. However, further studies, especially clinical trials, are required to confirm this.…”

The effects of flaxseed and tamoxifen on the inflammatory microenvironment in normal breast tissue and in breast cancer

“…Studies have shown that phytoestrogens suppress the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), alter the expression of proteins that control the cell cycle and apoptosis in breast cancer cell lines, and interfere with estrogen converting enzymes (68). Furthermore, flaxseed contains fatty acids, such as omega-3, which may have anticancer properties (76). An experimental model showed that flaxseed oil attenuated breast cancer growth and reduced cancer cell proliferation (77).…”

Phytoestrogens and the Intestinal Microbiome

“…Lignans are found in many plants. The most important source of precursors for enterolactone is flaxseed (Adlercreutz 2007, Calado et al 2018. The estrogenically active flavonoid 8-prenylnaringenin and its precursors are part of a complex of phenol compounds found in beer (Štulíková et al 2018).…”