Research on dietary sodium with invalid methods does not advance scientific understanding

Wuopio et al. (22:104, 2025) examined associations between urinary sodium excretion and metabolic markers using an invalid method (a spot urine sample and the Kawasaki estimating equation (‘spot method’)). The spot method has both high random and systematic error, and has been shown to produce spurious health outcome and disease association. Due to false controversy generated by studies using spot method, it has been recommended not to be used in research associating dietary sodium to health outcomes by major international and national scientific organizations and experts. Wuopio et al. are aware of the methods limitations and concerns about its use but in our opinion did not address these issues in their manuscript. The spot urine method represents a good example of how an inappropriate research method can undermine scientific understanding and generate false controversy.