To study the relationship between diet quality and 24 h urinary K excretion.

K was measured in 24 h urine samples, while diet was studied using a 24 h recall method over two consecutive days. Diet quality was determined using the Healthy Eating Index (HEI). The body weight, height and body composition of all participants were recorded, and the BMI of each calculated.

Representative members of the adult Spanish population from the FANPE Study (‘Fuentes Alimentarias de Nutrientes en Población Española’; Dietary Sources of Nutrients in the Spanish Population).

The final sample size was 329 participants aged 18–60 years.

Participants with a 24 h urinary K excretion ≥93 mmol/d (group AP = adequate potassium) had greater self-reported K intakes, consumed more fruit and vegetables, had a more varied diet and had better HEI scores than those with a 24 h urinary K excretion <93 mmol/d (group IP = inadequate potassium). A significant positive correlation was seen between 24 h urinary K and dietary variety and the number of servings of fruits, vegetables and dairy products consumed, and between each of these and the HEI after correcting for age, sex, BMI, coefficient of activity, energy intake and the under-reporting of energy intake. AP participants were less likely to have an inadequate diet (HEI score <50) than IP participants (OR =0·439; 95 % CI 0·201, 0·961; P=0·039).

Diet quality, measured by the HEI, is correlated with 24 h urinary K excretion in Spanish adults.