02/01/2024
Breast cancer Cure/What do you think?
Flaxseed and the Lignans
Flax (Linum usitatissimum), also known as linseed, belongs to the Linaceae family which originates from Europe, Asia, and the Mediterranean region. Flaxseed can be divided in two species: brown and golden. Golden flax develops in very cold climates, while brown flax develops in warmer and more humid climates. The latter must be ground to be better digested and absorbed by the body, thus increasing the bioavailability of the nutrients. It is considered a functional food that has nutrients with specific properties (antioxidant and/or antitumorigenic functions), such as omega-3 fatty acids, α-linolenic acid (LA), lignan, or fibers that are beneficial to one’s health, preventing some diseases, such as cancer and cardiovascular diseases, among others (14–16). Flaxseeds are rich in fiber and are suggested for situations of constipation, as they help to improve the intestinal function. They have omega-3 fatty acids that promote the reduction of cholesterol levels, thus preventing cardiovascular diseases. Additionally, they are still a good source of magnesium, phosphorus, manganese, vitamin B1, selenium, and zinc.
Although they are defined as one of the richest plant sources in omega-3 fatty acids, these seeds are also characterized by their lignan content. Although lignans are found in a variety of vegetable sources, such as whole grains, sesame seeds, vegetables, and fruits, flaxseeds have approximately 100 times more lignans than other foods (9, 17, 18).
Lignans are phytoestrogens that relieve the symptoms of menopause and can balance the effects of estrogen in the body by connecting to their receptors, as they have a very similar chemical structure as to an estrogen molecule (19).
The predominant lignan in flaxseeds is secoisolariciresinol diglucoside (SDG), making up around 95% of the seed’s lignan content. The remaining 5% consist of lariciresinol, pinoresinol, and matairesinol. After SDG lignan ingestion, bacteria in the colon act by converting the lignan into mammalian lignans, enterolactone, and enterodiol. These are structurally similar to estrogen, and have antioxidant activity and a weak estrogenic action (Figure (Figure1).1). It also works as an antiestrogenic because its structure is very similar to the main form of estrogen, which allows its binding to the cell’s receptors, thus inhibiting the growth of cancer cells (9, 20–23).
image.png
Breast tumors that contain estrogen receptors are called estrogen receptor positive (ER+) and tumors that lack estrogen receptors are estrogen receptor negative (ER−). Women who have ER+ tumors are more likely to respond to hormonal treatments than women with ER− tumors (24).
In our body, the biological active form of estrogen is estradiol, which is oxidized mainly in the liver to estrone. Estrone can be converted to two metabolites with different biological effects: 2-hydroxyestrone (2OHE1) and 16α-hydroxyestrone (16OHE1). While the first one has a small biological activity, the latter will increase the estrogen’s activity, promoting cell proliferation (growth of cancer cells) (Figure (Figure2)2) (25, 26). Women who produce more 16OHE1 are likely to have an increased risk of breast cancer (27).
image.png
Two clinical trials concluded that 28 postmenopausal women, who followed a diet including 10 or 25 g of ground flaxseed for 7 or 16 weeks, witnessed an increased level of excretion of 2OHE1 in their urine, without an increase in the excretion of 16OHE1. These studies imply that flaxseed can have some protective effects in postmenopausal women (28).
Omega-3 Fatty Acids and Breast Cancer
Polyunsaturated fatty acids (PUFAs) can be composed of omega-3 and omega-6. Linolenic acid and arachidonic acid (AA) are the main components of omega-6. The α-linolenic acid (ALA) is the precursor of the PUFA omega-3 family which forms eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (29, 30).
Omega-3 and ALA are also constituents of flaxseed. Flaxseed is considered as the best plant source of the essential omega-3 fatty acid. Studies suggest that the omega-3 fatty acid may have anticancer properties while omega-6 fatty acid can contribute to the development of cancer. Currently, in a regular diet, there is a higher amount of omega-3, than omega-6 (29, 30). Studies have revealed that PUFA omega-3 ingestion is associated with the reduction of risk of breast cancer (31). In animal studies, the ALAs have been shown to be able to suppress the growth, size, and proliferation of cancer cells. An increase in the death of these cells has also been observed (32, 33).
