Does Flaxseed Offer Any Benefit in Breast Cancer?

Success in breast cancer treatment and survival continue to improve. Greater public awareness, exercise, healthy eating and positive lifestyle changes clearly contribute. While trying to modify environmental factors, obtaining accurate information from reliable sources is equally important. For example, should flaxseed be recommended to breast cancer patients?

The Latin name of flax means very useful and is Linum usitatissimum. Flax fibers are used to make linen; its oil, rich in omega 3 fatty acids and known as linseed oil , is used in painting, while the defatted seeds are used as animal feed.

Health Effects of Flaxseed

Flaxseed contains lignans are the name of its hormone-like compounds; it is a highly concentrated source of phytoestrogens (soybeans are another source of phytoestrogens). Sesame seeds are also rich in lignans. Phytoestrogen means plant-derived estrogen: molecules structurally very similar to estrogen produced by the body. Flaxseed containing lignans has some positive effects on menstrual irregularities and menopausal symptoms, probably through hormonal effects. In addition, in polycystic ovary syndrome one study reported benefits through reduced androgen levels. Flaxseed contains alpha-linolenic acid (ALA), a building block of omega-3 fatty acids. Flaxseed or its oil is claimed to aid weight loss or lower cholesterol, but clinical trialshave not produced results proving these claims.

In breast and prostate cancer development, flaxseed can affect intracellular signals as has also been demonstrated. Because flaxseed has phytoestrogenic effects, patients with estrogen receptor -positive (ER +) breast cancer should not use it. Contrary to claims in online news, flaxseed supplementation is not therapeutic in breast cancer; rather, it poses potential danger to breast cancer patients.

Where Did the Idea That Flaxseed Might Help in Breast Cancer Originate?

Laboratory studies have observed anticarcinogenic (tumor-shrinking) effects of flaxseed lignans independent of their phytoestrogenic effects.

In humans, lignans are metabolized by intestinal flora (microbiome) into enterolactone. A few studies suggested that people with higher serum enterolactone levels had lower breast cancer risk. These findings raised the question of whether flaxseed might help in breast cancer.

Based on these findings, should we encourage breast cancer patients to supplement with lignan-containing foods such as flaxseed and sesame?

A similar debate occurred with beta-carotene and lung cancer. Some studies in the 1980s suggested that beta-carotene was useful in lung cancer treatment. These early studies encouraged more frequent and greater consumption of beta-carotene-containing fruit and vegetables. However, larger studies showed that beta-carotene supplements, far from protecting against lung cancer, increased its likelihood particularly in smokers. Many lives were arguably saved when larger studies overturned approaches supporting beta-carotene supplementation.

In conclusion, It is important to understand how and to what extent serum enterolactone levels reflect dietary lignan intake. The amounts of lignans obtained from different foods are also not yet fully understood. We do not know how lignans interact with smoking, alcohol and other dietary factors. There are therefore no satisfactory study findings supporting dietary lignan supplementation to increase serum enterolactone concentrations. Given their phytoestrogenic structure, potential risks should be considered, and people diagnosed with breast cancer in particular should avoid flaxseed supplements.