This randomized, double blind, controlled trial investigates changes in the cardiovascular index (triacylglycerol/HDL-cholesterol × waist/hip ratio) after 12 weeks of marine protein hydrolysate (MPH) or whey protein powder (placebo) supplementation in adult healthy persons. Additionally, the study investigates potential effects on plasma parameters of metabolic health including lipids, glucose, inflammatory parameters and redox state, as well as associations between dietary MPH and body weight, abdominal obesity, body composition, and gut microbiota composition. Finally, putative end-products of diet-microbial interactions (TMAO and short-chain fatty acids) with CVD risk factors and biomarkers of mitochondrial function are examined.

Marine protein sources, including fish and fish protein hydrolysates, may have particular health benefits. Health benefits from fish consumption have been attributed to the n-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Proteins from marine sources may contain valuable bioactive components, with amino acid composition and protein profiles that differ from terrestrial sources. Generally, the dietary source of protein can affect cellular energy metabolism, and hydrolyzed peptides can have potent and specific bioactive potential.

Rest raw materials (RRM) from cod (Fjordlaks AS, Norway) are used for the hydrolysis production (Food Grade). Freshly minced RRM were treated with enzymes optimized to generate bioactive hydrolysates using facilities and techniques approved for human consumption. The investigational products are given in a dose of 18 g protein per day, corresponding to the protein content of a standard meal, and similar to doses recommended in a range of protein supplements.

The study enrolls around 70 men and women age of 20-80 years with waist circumference of < 102 cm for men and < 88 cm for women. Prospective study participants were informed of the study and invited to participate through advertising primarily in social media (Facebook advertisement, geographically limited to 12 km surrounding the city centers of Bergen and Ålesund). Participants provided written informed consent, and were screened via self-reporting in an online form in EasyTrial hosted by the Research Unit for Clinical Trials at the University of Bergen. Data collection by the study staff at baseline verifies inclusion and exclusion criteria and participant eligibility prior to randomization. The potential participants are informed about practical details at a digital or physical meeting 1-2 weeks prior to baseline.

Groups of participants (40-60% males/females) are block randomized to the two treatments using randomly selected block sizes, and stratified according to sex.

The participants are given a container with the powder sufficient for the entire study period, and a spoon to measure the intake at breakfast (6 g), lunch (6 g) and supper (6 g), or morning (9 g) and evening (9 g) according to individual preference. The patients will mix the powder products in water or mineral water. Flavours have been masked by supplementation with beet powder, and mixing 0.5 g fish hydrolysate per serving in the placebo, to minimize differences in taste of the placebo and active product.

Inclusion Criteria:

• Healthy female and male subjects at age 20-80 years old understanding Norwegian oral and written information
• Waist circumference for males < 102 cm and females < 88 cm

Exclusion Criteria:

• Pregnancy or lactation
• Having used high-dose omega-3 PUFA supplements (>2 g/day) less than 28 days prior to randomization
• Use of corticosteroids that will influence protein metabolism
• Antibiotic treatment previous 3 months
• Alcohol or drug abuse or any conditions associated with poor compliance
• Medical diagnosis of malabsorption disorders, Crohn's disease, or lactose intolerance
• Scheduled hospitalization during the course of the study that could compromise the study
• Diabetes type I or II, serious high blood pressure at screening, serious infections, diseases requiring medication that can influence the study
• Known or suspected sensitivity or allergic reactions to the IMP or excipients
• Presence of other major medical or psychiatric illness that would affect the ability to participate in the study or put the subject at increased risk
• Intake of statins. If needed to obtain the recruitment goals, we will accept people using a low dose of statin

The groups will be randomly labelled A or B. Neither participants, care providers or statistician will know the treatments of the groups before the statistical analyses for the primary outcome have been completed.