To Your Health

What are lignans?

Q. What are lignans? The maker of my vitamin E supplement "improved" it by adding sesame lignans. How do they help vitamin E to work and do they have any other benefits?

A. Lignans are among the many phytonutrients, beneficial plant compounds that are not classified as vitamins. There are numerous plant sources of lignans such as sesame seeds, pumpkinseeds, cranberries, and black or green tea, but easily the richest and most studied lignans are from flaxseeds.

The friendly bacteria in our intestines convert all the various plant lignans into one of two other "human" lignans that have weak estrogen activity, similar to the isoflavones derived from soy products. When there is very little estrogen in the body, for instance after menopause, these weak lignan estrogens make up some of the insufficiency. When natural estrogen is abundant, lignan estrogens appear to reduce the activity of natural estrogen by occupying the estrogen-binding sites on cell surfaces without having much estrogen effect. As a result, recent research indicates that lignans may be capable of inhibiting the formation of cancers such as many breast and colon cancers that depend on estrogen to start and develop.

Early evidence suggests that lignans may be useful in treating chronic kidney disease. Lignans may also be antioxidants, although their potency is not yet clear. Preliminary research suggests that flaxseed lignans may help protect against atherosclerosis, either directly or by reducing the high cholesterol that is a risk factor for producing plaque in arteries.

Recently the lignans in sesame seeds have attracted attention. Flaxseeds and sesame seeds both contain considerable amounts of lignans. Both contain more than 40% fat, which aids in the absorption of fat-soluble vitamins such as vitamin E, but may not otherwise affect vitamin E function. However, the predominant fatty acid in flaxseeds is alpha linolenic acid, an omega-3 fatty acid, while sesame seeds contain mostly linolenic acid, an omega-6 fatty acid. This would seem to give flaxseeds the health advantage since Americans would benefit from more omega-3. But research published in the journal Lipids in December of 2003 indicates that sesame lignans – but not flax lignans – improve vitamin E function, apparently allowing "used" vitamin E to be recycled and reused as an antioxidant.

Sesame seeds deserve greater exposure than only being found atop hamburger buns. They may be the oldest condiment known to man, dating back several millennia, and today they provide the nutty taste and delicate crunch to many Asian dishes. Sesame seeds are a very good source of many essential minerals – calcium, magnesium, and zinc in particular. Sesame seeds are not among the common allergenic foods, often contain little or no pesticide residues, and do not contain substances such as oxalates, which are troublesome to some individuals. Roasting sesame seeds improves their flavor and does not decrease the amount of lignans absorbed by the body.

Sesame seeds are widely available, but they tend to become rancid, so they should be stored in the refrigerator or freezer.

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