Relationship between Urinary Phytoestrogen Metabolites and Telomere Length: A Cross-Sectional Study from NHANES

Existing studies suggest that foods rich in phytoestrogens could reduce mortality and protect against the shortening of telomere length (TL). However, the specific phytoestrogens responsible for this effect remain unidentified. We conducted a cross-sectional study using data from the 1999-2002 U.S. National Health and Nutrition Examination Survey. Four metabolites of soy isoflavones (daidzein, equol, genistein, O-DMA) and two metabolites of lignans (enterodiol and enterolactone) were detected. Leukocyte TL was measured. After ln-transformed, the association of phytoestrogen metabolites and leukocyte TL were assessed using multivariable linear regression. Percentage change was calculated as (eβ-1) × 100%. Of the 2,607 participants, 48.52% were male. A 1-SD increase in urinary equol was associated with a 1.50% (95% CI: 0.51-2.50) increase in TL, and TL was 4.26% (95% CI: 1.07-7.56) longer in the highest quintile of equol compared to the lowest. Similarly, a 1-SD increase in the equol-to-daidzein ratio was linked to a 1.87% (95% CI: 0.91-2.84) rise in TL, and TL was 4.83% (95% CI: 1.71-8.05) longer in the highest quintile of the equol-to-daidzein ratio compared to the lowest. No significant association of urinary daidzein, genistein, O-DMA, enterodiol, and enterolactone with TL was observed. Our findings suggested that higher levels of urinary equol and its ratio with daidzein were associated with longer leukocyte TL, highlighting the need for further research into their relationship with aging.