Eat Your Lignans

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Remembering to eat foods like broccoli, flax and berries is important for keeping your memory sharp. Several small studies have suggested that phytoestrogens from plants can play a role in maintaining mental abilities, and now a larger study from the Netherlands supports those claims for postmenopausal women.

The study’s most significant finding was the identification of the lignans as the most important group of phytoestrogens for cognitive functioning. Lignans are a specific type of phytoestrogens found in oilseeds such as flaxseeds, pumpkin seeds and sunflower seeds; whole grains; berries; tea; and vegetables, such as broccoli. The other major category of phyto-estrogens is the isoflavones, which mainly are found in soy and soy products, beans and peanuts.

Using a food frequency questionnaire, the dietary intake of phytoestrogens over the previous year was determined for 403 postmenopausal women. Known values of isoflavones and lignans were assigned to each food item on the questionnaire.

Cognitive function, which mainly involves memory and mental abilities, was determined using a questionnaire called the “mini mental state exam.” Decreased scores on this test are associated with Alzheimer’s disease and other age-associated memory problems.

Examination and statistical analysis of the data showed that higher dietary intake of lignans was associated with better cognitive function in postmenopausal women. Isoflavone intake, however, was not related to this increased cognitive function. The group who ate more lignans had a 49 percent higher rate of intact cognition, whereas the isoflavone group had only a 12 percent higher rate of intact cognition. This effect was more pronounced in women with a longer postmenopausal time span (20 to 30 years). In this group of women, increased consumption of lignans increased the rate of intact cognition by 103 percent, while increased consumption of isoflavones increased rates of intact cognition by only 14 percent. Researchers did not say exactly what amount of lignans was necessary for higher cognition. This study is still too preliminary to suggest a level.

Phytoestrogens found in plants have a chemical structure similar to that of the hormone estrogen, allowing them to have some similar effects in a woman’s body. A number of mechanisms are proposed for the action of phytoestrogens on the ability to think clearly. These include the ability of phytoestrogens to promote the health of the blood vessels, to act as antioxidants and to interfere with signal transduction mechanisms within the cell. Among other things, improving mental capacity is one reason why some women choose estrogen replacement therapy. Increasing dietary consumption of lignans may be sufficient for this purpose.

Source: Higher Dietary Intake of Lignans is Associated with Better Cognitive Performance in Postmenopausal Women. Franco, O.H., et al. The Journal of Nutrition. 135:1190-1195, 2005.

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