To determine associations between household food security status and risk of Cu toxicity.

A population-level cross-sectional study to determine adult household food security status and its relationship with serum total Cu concentration (serum Cu) using multivariable regression models.

Adult participants in the US National Health and Nutrition Examination Survey (NHANES) 2011–2014.

The NHANES phlebotomy data, a nationally representative sample (n 2780; 1360 men and 1420 women), were analysed.

A significantly greater proportion of food-insecure persons had serum Cu that was above the upper value of the normal range (clinical cut-off) compared with their food-secure counterparts. In men, food insecurity (OR = 2·24, P < 0·001) and marginal food security (OR = 1·79, P < 0·001), and in women, marginal food security (OR = 1·82, P = 0·016), associated with greater likelihood to have serum Cu that was above the upper value of the normal range. Food insecurity was significantly associated with greater likelihood (OR = 1·65, P = 0·020) to have serum Cu that was within the upper quartile (≥75th centile).

Food-insecure persons associate with higher serum Cu concentration and are at greater risk of Cu toxicity. There is need to study the sources of Cu in general, and specifically in food-insecure persons, to facilitate reduction of Cu exposure. Examining Cu contents of the food and water supplies could explicate any relationships to food insecurity and Cu intake.