A public health intervention is action taken by authorities to reduce a risk to the health of the population. In the food sphere this ranges from ordering a product recall and closing an insanitary premises, through issuing dietary advisories during a contamination incident, to long-term measures such as mandatory fortification, salt-reduction targets agreed with industry, and restrictions on advertising unhealthy foods to children. Interventions are chosen on evidence of risk and effectiveness, and they sit on a ladder from voluntary guidance up to legislation, with more intrusive steps justified by greater danger. Their impact is judged by surveillance data: falling infection rates, lower average blood pressure, or fewer deficiency cases. Good interventions combine clear communication with enforcement so the public understands both the risk and the reason for action.