Estrogens (female sex hormones) play an important role in the development of breast cancer. When the level of these hormones is too high, there is excessive stimulation of the growth of the mammary glands and a parallel increase in the risk of cancer (we then say that breast cancer is hormone-dependent). Some types of plants contain molecules that have an estrogen-like structure. These molecules, called “phytoestrogens” exert several positive effects on the metabolism of human estrogens, in particular by reducing the blood levels of these hormones as well as by preventing them from binding to the surface of the mammary cells. These combined effects reduce the negative effects associated with estrogen and, by extension, reduce the risk of breast cancer.
Lineages: phytoestrogens like no other
There are three main types of phytoestrogens:
1) isoflavones, present exclusively in soy;
2) coumestans, found in particular in alfalfa and clover
3) lignans, present in several fruits and vegetables as well as certain cereals.
However, the two main lignans, secoisolariciresinol and matairesinol, are particularly abundant in flaxseed, with levels up to 3,000 times higher than in other plant products.
Unlike other classes of phytoestrogens, lignans are not absorbed directly into the bloodstream, but rather must be metabolized first by the intestinal bacterial flora. The products of this metabolism, namely enterolactone and enterodiol, have a lower affinity for estrogen receptors than other phytoestrogens, but, on the other hand, have additional anticancer properties that could help counter the development of breast cancer. breast.
Eating flaxseed reduces the risk of breast cancer by 20%.
Such a protective effect of lignans is supported by a recent analysis of epidemiological studies relating to the impact of these molecules on the risk of breast cancer. By carefully examining the results obtained in the context of 13 studies carried out on postmenopausal women (the group most at risk of breast cancer), the researchers observed that women with the highest dietary intake of lignans had a risk of breast cancer nearly 20% lower than those who consumed very little.
These observations are in agreement with the results of several studies carried out on animals bearing mammary tumors where the addition of lignans to the diet is associated with a significant reduction in the development of these tumours.
Although most plant products contain lignans, regular consumption of freshly ground flaxseed is the best way to get a high lignan intake. However, other sources should not be overlooked, including cruciferous vegetables (broccoli,) or green tea, because, in addition to their lignan content, these foods also contain large amounts of other anti-cancer molecules that can actively participate in blocking the growth of breast cancer cells.
Milder et al. Br. J. Nutr.93: 393-402
Buck et al. Meta-analyses of lignans and enterolignans in relation to breast cancer risk. Am. J. Clin. Nutr. 92: 141-153.