A rye bran diet, rich in plant lignans, has no influence on the composition of the gut microflora in postmenopausal women

The consumption of phytoestrogens has been related to a reduced risk of hormone-dependent cancer types as well as coronary heart diseases. Plant lignans that represent one class of phytoestrogens are found in relatively high concentrations in rye bran. When consumed, they are metabolized into mammalian lignans (enterodiol and enterolactone) by gut bacteria. In order to investigate whether an increased intake of plant lignans had an impact on the composition of the predominant bacterial community of the human gut a 2×6-week intervention study, with a crossover design, was conducted. Eighteen healthy postmenopausal women (age 55–71 years) were recruited and randomly assigned to two groups. The intervention comprised bread products with either rye bran or an inert wheat cellulose (Vitacel®). Faecal samples were collected before and at the end of each intervention period and analysed for their predominant bacterial species composition by a cultivation-independent approach – polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The rye bran diet had no impact on the composition of gut microflora. However, the DGGE profiles demonstrated unique bacterial communities for each individual, which implied a differing efficiency among individuals to metabolize lignans.