Traditional living in the Amazon: Extended breastfeeding, fish consumption, mercury exposure and neurodevelopment

Background: Features of traditional living in the Amazon Basin (high fish consumption and long breastfeeding) are likely to expose children to Mercury (Hg). Aim: To study neurodevelopment in 690 children in relation to prolonged breastfeeding and mercury exposure. Subjects and methods: Three groups of breastfeeding children were formed: Group 1 (breastfed for 6 months), Group 2 (7-12 months) and Group 3 (extending up to 24 months). Neurodevelopment was assessed as age of walking, age of talking and the Bayley Scales of Infant Development-BSID. Mercury exposure was assessed from Thimerosal-containing vaccines and fish consumption from hair Hg (HHg). Results and conclusions: HHg increased in children and decreased in mothers at 24 months. Frequency of fish consumption was significantly correlated with maternal HHg at birth (Spearman's r=0.8583; p=0.0001); likewise, there was a significant correlation between duration of breastfeeding and children's HHg (Spearman's r=0.15; p=0.0018). Extended breastfeeding did not influence the Mental Development Index-MDI or Psychomotor Development Index-PDI, but maternal education and HHg (marker of fish consumption) interacted positively and significantly with both. Frequency of maternal fish consumption and education had a positive association with BSID scores; it is speculated that maternal education and nutrients in fish have an opposing effect on Hg exposure.