MINNEAPOLIS, US: Since the election of Donald Trump as US president in 2024, the question of water fluoridation in the country has become increasingly politicised. This is largely because Secretary of Health and Human Services Robert F. Kennedy Jr has consistently contradicted the scientific community by linking the measure to a range of health problems, including reduced IQ. As a timely investigation into this fraught issue, a major nationally representative US study has examined whether typical levels of fluoride exposure in childhood—those found in municipal water systems operating within public health guidelines—are associated with cognitive outcomes in adolescence and later adulthood. The research provides important evidence for ongoing debates about water fluoridation policy.