Lignans are a group of phytonutrients that are found in healing foods like seeds, grains, and vegetables. A recent study suggests that boosting your nutritional health with these nutrients could help protect against cancer.

A research team at the German Cancer Research Center, in Heidelberg, Germany, examined whether lignans, the most important class of phytoestrogens in the Western diet, could protect against breast cancer. The reviewed studies were published between 1997 and August 2009. Then they calculated cancer risk estimates for total lignan exposure, dietary lignan intake, and status of tumors.

The researchers found 21 studies to incorporate into their review. They found that, in postmenopausal women, high lignan intake was associated with a significant reduced risk of breast cancer. In fact, in one of the studies, 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.

Breast cancer risk was also inversely associated with enterolignan exposure. They concluded that high lignan exposure may be associated with a reduced breast cancer risk in postmenopausal women.

The research team is unclear 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, take this health advice: add some to your diet now and gain the other health benefits these compounds have to offer.

Here are your top five sources of lignans:

• Flaxseed (particularly high in lignans)
• Sesame seeds (also very high in lignans)
• Green tea (another excellent source)
• Berries
• Whole-grain cereals

These five sources are probably your best options to boost lignan intake. Keep in mind that the healthful nutrients can also be found in whole grains, some other fruits, and a number of vegetables, such as broccoli and kale.

One final note: flaxseed yields about 800 micrograms/gram of lignans, but the oil has little or no lignans.

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