More support that lignans may cut breast cancer risk

High intake of lignans from the diet could reduce the risk of breast cancer by almost 30 per cent, suggests a new epidemiological study from France.

Plant lignans, found widely in plants and seeds, such as flax seed, whole grain cereals, berries, vegetables and fruits, are metabolised in the colon by microflora into enterodiol and enterolactone.

Lignans are well-known phytoestrogens - active substances derived from plants that have a weak oestrogen-like action, and have been linked before to breast health, as well as offering benefits for postmenopausal women.

The new prospective study, published in the March issue of Journal of the National Cancer Institute, investigated the dietary intakes of four plant lignans using a self-administered diet history questionnaire in 58 049 postmenopausal French women not taking soy isoflavone supplements.

After an average of 7.7 years of follow-up, the researchers documented 1469 breast cancer cases. After adjusting for potential confounding factors, the researchers report that a daily intake greater than 1395 micrograms was associated with a 17 per cent reduction in breast cancer risk, compared to the lowest daily intake.

The inverse associations were limited to ER- and PR-positive breast cancer, said the researchers, with the highest intake of total lignans associated with a 28 per cent reduction of these cancers.

Last year a study published in the European Journal of Cancer Prevention (Vol. 15, pp. 225-232), reported that women with high plasma levels of enterolactone (above 12.96 nanomoles per litre), linked to high lignan intake, was associated with a 58 per cent reduction of breast cancer risk.

In addition, Lilian Thompson, a professor in the Department of Nutritional Sciences at the University of Toronto, is a world-renowned researcher in the area of lignans. In one of her recent studies published in the Journal Clinical Cancer Research, women with newly diagnosed breast cancer who consumed a daily muffin containing 25 grams -- two tablespoons -- of flaxseed had a significant reduction in tumour growth compared with those who ate muffins containing no seeds. The tumours were measured at the time of diagnosis and then again, at the time of surgery. According to the researchers, the effect of the flax on the cancerous cells was comparable with that seen using chemotherapy -- with no side effects.