Study population
The study was conducted at the Institute of Food Science, Technology and Nutrition (ICTAN-CSIC) according to the guidelines laid down in the Declaration of Helsinki. It was approved by the Ethics Committee of the Spanish National Research Council (CSIC), Madrid, Spain (2021/03/05, Ref. 046/2021) and the Ethics Committee for Clinical Research of the Hospital Puerta de Hierro-Majadahonda, Majadahonda, Spain (2021/03/08, Ref. PI176/19). It was registered in the Clinical Trials database (ClinicalTrials.gov ID: NCT04278482). Before the study began, participants received information about the study and the day they attended the first visit at the institute they signed an informed consent form expressing their agreement to participate in the study.Participants were recruited via poster advertisements and a direct mailing sent to academic, social, health, and research institutions. The study was carried out between March and July of 2021 in Madrid, Spain. The inclusion criteria were: healthy adults aged 18–45, consumers of a vegetarian diet (for at least 6 months) or an omnivorous diet with low fish intake, below the Spanish current dietary recommendation of at least 2 servings/week [