Breast Cancer Risk and Treatment: A Review of Evidence from Flaxseed and Other Selected Foods

Breast cancer is a significant global health problem, with high incidence rates and associated mortality (DeSantis et al., 2019). The dietary intake of specific substances, such as flaxseed, broccoli, sesame seeds, phytoestrogens, lignans, pumpkin seeds, and beans, may influence breast cancer risk and progression. This article reviews the available evidence on these dietary substances, particularly focusing on flaxseed. We will also consider their potential interactions with breast cancer drugs and their role in the broader context of breast cancer management.

Flaxseed and breast cancer

Flaxseed (Linum usitatissimum) is a rich source of lignans and omega-3 fatty acids, both of which have been associated with anticancer properties (Adolphe et al., 2010). Its main lignan, secoisolariciresinol diglucoside (SDG), is metabolized in the gut into enterodiol and enterolactone, both showing antiestrogenic and antioxidant effects (Hutchins et al., 2001).

A recent review from the University of Toronto investigated the potential benefits of flaxseed and its constituents in reducing breast cancer risk and tumor growth (2023, yet to be published). The authors concluded that flaxseed intake seems to lower breast cancer risk and inhibit tumor growth in preclinical models. Furthermore, they found no evidence of negative interactions with breast cancer drugs like tamoxifen, potentially due to the synergistic effects of flaxseed lignans and these pharmaceuticals.

Other dietary substances and breast cancer

Phytoestrogens are plant-derived compounds with structural similarity to human estrogen, found in various foods such as soybeans, sesame seeds, and flaxseeds. Some phytoestrogens are classified as lignans, which have shown potential anticancer effects. Lignans may act as aromatase inhibitors, reducing the conversion of androgens into estrogens and thereby potentially decreasing breast cancer risk (Adlercreutz et al., 2002).

Similarly, substances found in broccoli, known as sulforaphanes, have been reported to inhibit breast cancer cell growth and proliferation (Liu et al., 2013). Pumpkin seeds, rich in phytoestrogens and other bioactive compounds, may also play a role in breast cancer prevention and treatment, though more research is needed in this area.