In this Randomized Controlled Trial (RCT) we want to study how supplements of cetoleic acid ( C22:n1-11) (intervention) affect the conversion of alpha-linolenic acid (ALA) to EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) in healthy subjects, compared to supplements with a low concentration of cetoleic acid (control).

Our primary endpoints are changes in the concentration of EPA and DHA in plasma and red blood cells.

This is a randomized double-blinded controlled trial ( randomized 1:1). Study population: healthy men and women 20-70 years, BMI 20-35 kg/m2.

Study design:

• 3 weeks run-in-period where all participants consume control capsules every morning.
• Randomization intervention: control (1:1). All participants consume their capsules (control or intervention) for 4 weeks.

The intervention oil consists of a fish oil high in cetoleic acid and the control oil is a mix of different oils and low in cetoleic acid.

Power calculation and sample size:

It was expected a difference of 15% in n-3 between the groups after the intervention (Østbye et al. 2019, doi:10.1017/S0007114519001478).

The level of significance was set to 5% (two-sided) and the power to 80%. A total of thirty-eight subjects were required to participate in the study, but a high dropout rate was expected (20%) and it was considered necessary to include a total of seventy (n=70) subjects (thirty-five per arm).

Inclusion Criteria:

• BMI 20-35kg/m2
• opportunity to meet for 3 visits at the Department of Nutrition, University of Oslo, during the study period.

Exclusion Criteria:

• Chronic disease (liver/kidney/metabolism)
• Alcohol overconsumption (>40g/day)
• Diabetes and high fasting blood glucose
• Pregnant/ breastfeeding or planning pregnancy during the study period
• High fish intake (>3 meals/week).
• Blood donation during the study period
• Difficulty following the study protocol.
• Smoking/snuffing
• Regularly use of anti-inflammatory drugs
• Regularly use of omega-3 supplements /cod liver oil.

Data will not be sheared as individual participant data, but the results will be shared on group levels. All participants information are treated deidentified

All participant, the major investigator, study coordinator and the study staff are blinded for the randomizing. The capsules and capsule containers will only be identifiable by the ID (identifying) numbers on the containers.

Allocation of participants to the specific intervention group is carried out by a statistician and one person not involved in conducting the study.