ASSESSMENT OF DATA ON THE LIGNAN CONTENT OF FOODS

Authors: Meagher, Lucy; Beecher, Gary

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2000
Publication Date: 6/1/2000
Citation: Meagher, L.P., Beecher, G.R. 2000. Assessment of data on the lignan content of foods. Journal of Food Composition and Analysis. 13:935-947.

Interpretive Summary: Plant-derived foods contain minor constituents, some of which may have health benefits. One family of these constituents are the lignans which are converted in the gastrointestinal tract to compounds that have both estrogenic and antiestrogenic properties. Increased consumption of lignan-rich foods has lead to the need for tabular data on the lignan content of foods. To date, the lignan content of foods has been measured by two methods. The direct method involves the extraction of lignans and/or hydrolysis of lignan glycosides followed by analysis of the resulting aglycones, primarily secoisolariciresinol (SEC) and matairesinol (MAT). The indirect method utilizes in vitro digestion with fecal microflora followed by analysis of enterodiol (ED) and enterolactone (EL), which are the metabolic products of SEC and MAT. The current research reports a compilation of the available data on the lignan content of foods and the assessment of these data by comparing the results of the direct and indirect methods. The highest concentration of lignans was observed in flaxseed. Several vegetables, including squash, broccoli, carrot and asparagus, contain substantial levels of lignans with low levels in cereals, fruits, legumes, oil seeds and some vegetables. In general, the indirect method of analysis gave higher values than direct analysis for most foods for which comparisons could be made. This compilation provides nutritionist and dieticians with a convenient source of lignan values for the development of diets, and the assessment of intake.

Technical Abstract: The plant lignans, secoisolariciresinol (SEC) and matairesinol (MAT) are converted to the metabolites, enterodiol (ED) and enterolactone (EL), known as the mammalian lignans in the gastrointestinal tract. In vitro, mammalian lignans may have both estrogenic and antiestrogenic properties. Increased consumption of lignan-rich foods through the addition of brans, oilseeds and cereals in bread, muffins, health bars and breakfast cereal or emphasis on fruits and vegetables in a balanced diet has lead to the need for reliable data on lignan content in foods. The quantitative determination of the lignans to date by a direct method has involved hydrolysis of the glycoside and analysis of the resulting aglycones (SEC and MAT). The in vitro fermentation methodology, which simulates colonic fermentation with fecal microflora has been utilized in the indirect analysis of foods where ED and EL are measured as an indication of the plant lignans. A compilation of the available data on the lignan content of various food groups, and the assessment of these data by contrasting two different analytical methodologies is given. In general, in vitro fermentation gave higher values, compared to direct analysis, for most foods for which comparisons could be made.