—by Cate Stevenson, BA
Lignans are a group of phytonutrients that are found in seeds, grains and vegetables. Flaxseed is one of the richest sources of plant lignans. A recent review of clinical trials suggests that these lignans could help protect against cancer.
In an analysis of 21 studies published in the past 13 years, researchers found that postmenopausal women who reported the highest intakes of dietary lignans were 14% less likely to develop breast cancer than those with low intakes.
For the study, a team of scientists at the German Cancer Research Center combined the results of 21 previous studies on lignan intake and breast cancer risk. For some of the studies, researchers also took blood or urine samples to measure participants’ levels of enterolignans — compounds created when intestinal bacteria interact with dietary lignans.
Although the researchers found no relationship between women’s lignan intake and their risk of breast cancer, when they separated the women by menopause stage, they found that high lignan intake showed a lower risk of breast cancer.
In one of the studies, for example, a quarter of the women with the highest lignan intake were 17% less likely to develop breast cancer during the study period compared with the one-quarter with the lowest intake. These results remained consistent even after the researchers accounted for a number of other factors in breast cancer risk including age, family history, weight and history of estrogen exposure from birth control pills or hormone replacement therapy.
The researchers suggest that lignans (and other phytoestrogens) might protect against breast cancer by inhibiting the body’s own estrogen activity. Another possibility is that these healthy compounds have powerful antioxidant effects.
The research team is unclear as to why lignan intake would have different effects in pre- and postmenopausal women. One possibility, they suggest, is that any protective lignan activity is only effective when women’s natural estrogen levels are relatively lower, as they would be after menopause.
Although more studies need to be conducted to prove a definitive link between lignans and cancer prevention, add some to your diet now and gain the other health benefits these compounds have to offer. Flaxseed and sesame are particularly high in lignans and are probably your best sources to boost intake. Lignans can also be found in whole grains, berries and some other fruits, as well as a number of vegetables such as broccoli and kale, and green tea.