Participants
RECRUITMENT, BLIND
Participants were men and women aged 18–55 years with a body mass index (BMI) between 18 and 25 kg/mSubjects were recruited between November 2017 and January 2018 at the Institute of Food Science, Technology and Nutrition (ICTAN). Recruitment was carried out mainly at the campus of Complutense University of Madrid (UCM) by placing flyers in the faculties, research institutes, and through talks after lectures, also through websites and internet. Potential volunteers were informed by phone, e-mail or in person at ICTAN. Subjects who met the inclusion criteria were invited to an on-site visit and interviewed about their medical condition and dietary habits. They also provided a recent blood analysis to confirm TC concentrations or referred to a collaborating laboratory (Unilabs S.L., Madrid) for this analysis. This biomarker (TC concentration) was the main variable for allocating participants in the normocholesterolemic or hypercholesterolemic groups. Thus, of the 146 subjects interviewed, 72 volunteers were recruited, corresponding to 37 healthy subjects (NC group) and 35 at-risk subjects (HC group) (Fig. Study flowchart according to CONSORT (Consolidated Standards of Reporting Trials)Randomization of participants was done by generating random numbers using Microsoft® Excel 2016 program. It was controlled by the health status (i.e. NC or HC) and within each group, subjects were allocated (to the OPO or HOSO interventions) to sequence order in a 1:1 ratio, due to the crossover design of the study. Assignment of codes to participants, randomization and allocation to each oil were carried out by different team members. Samples were coded according to the study visit number to conceal treatment allocation during handling and analysis. Oils (OPO, HOSO and SO) were bottled in un-marked bottles with different cap colours. Participants were blinded to the type of oil they consumed in each intervention phase. They were habitual consumers of VOO or EVOO and were not familiar with OPO and HOSO. Therefore, it can be assumed they were not able to infer which oil was used in each intervention stage despite differences in colour and taste of OPO and HOSO.To estimate sample size, the G*Power 3.1.9.7 program was used. We considered TC concentration as the main variable and that the study design (randomized, blind, crossover, controlled intervention), in which the same subjects consumed the test (OPO) and control (HOSO) oils. Other premises considered were differences by treatment, a statistical power of 80%, a level of significance of 0.05, two tail, standard deviation of 25, mean of pre-post differences of 15 units, and an effect size of 0.54. Considering all these parameters, a final sample size of 30 volunteers was established for group. Finally, the number of participants were NC (normocholesterolemic) = 34 and HC (hypercholesterolemic) = 30.