An affordable heart-healthy dietary approach is essential for the management of familial hypercholesterolaemia (FH); however, the optimal dietary pattern and the role of adjunctive nutrient supplementation remain uncertain. This study aims to evaluate the effects of the Brazilian Cardioprotective Diet (DICA Br), adapted from the Portfolio Diet, with or without phytosterol and/or krill oil supplementation in individuals with probable or definite FH according to the Dutch Lipid Clinic Network (Dutch MEDPED) criteria.

The DICA-FH study is a national, multicentre, randomised, factorial, parallel-group, superiority, placebo-controlled clinical trial with a 1:1:1:1 allocation ratio. Participants aged ≥16 years receiving age-appropriate lipid-lowering therapy will be randomised into four groups: (1) adapted cardioprotective diet (DICA-FH) plus phytosterol placebo and krill oil placebo; (2) DICA-FH plus phytosterol 2 g/day and krill oil placebo; (3) DICA-FH plus phytosterol placebo and krill oil 2 g/day or (4) DICA-FH plus phytosterol 2 g/day and krill oil 2 g/day. All participants will undergo whole-genome sequencing and receive appropriate genetic counselling. Primary outcomes will be means of low-density lipoprotein cholesterol and lipoprotein(a) levels after 120 days. Secondary outcomes will include additional lipid biomarkers, adherence to protocol and adverse events. The planned sample size is 300 participants. Follow-up is expected to conclude in July 2026.

This study was registered under CAAE 65549622.2.1001.0060 and received ethical approval from the Hcor Research Ethics Committee (approval number 5.805.072) and the Brazilian National Research Ethics Commission (CONEP; approval number 6.864.951). Written informed consent will be obtained from all participants prior to enrolment. The study findings will be disseminated through peer-reviewed publications, scientific conferences and channels aimed at the general public.

NCT06331195.