Soy isoflavone consumption and age at pubarche in adolescent males

Purpose Isoflavones have estrogenic properties that may adversely affect pubertal development of boys. We examined if soy isoflavone consumption is associated with age at pubarche (first onset of pubic hair) in a male population with a wide range of soy intake. Methods Boys aged 12-18 years (n = 248) who attended schools around Adventist universities in Southern California and Michigan self-reported their age at pubarche. Intake of soy isoflavones was assessed using a validated Web-based food frequency questionnaire; consumption levels were designated as low, moderate, and high. Descriptives, time-to-event analysis, and Cox proportional hazards regression that controlled for confounders were performed. Results Energy-adjusted mean intakes were 0.8-54.9 mg/d for total isoflavones, 0.4-22.1 mg/d for daidzein, and 0.4-28.0 mg/d for genistein. Moderate and high total soy isoflavone intake were significantly associated with earlier adjusted median age at pubarche: 12.58 years [RR (95% CI): 1.58 (1.06, 2.36)] for moderate and 12.50 years [RR (95% CI): 1.63 (1.03, 2.60)] for high vs. 13.00 years for low consumers. Similarly, daidzein and genistein consumption was also significantly associated with age at pubarche. No significant associations were found for facial hair for any of the isoflavones. Conclusions Age at pubarche in this male population widely exposed to soy is within the reported range for boys' pubarcheal age; moderate/high consumers tend to have it earlier compared to low consumers. Further studies are needed to ascertain that substantial exposure to soy isoflavones does not adversely affect pubertal development of boys.