Salmon fish protein supplement increases serum vitamin B12 and selenium concentrations: secondary analysis of a randomised controlled trial

PURPOSE: The main aim of the present study was to examine the effect of a fish protein supplement made from by-products from production of Atlantic salmon, on blood concentration of micronutrients. METHODS: We conducted an 8-week double-blind parallel-group randomised controlled trial. In total, 88 adults were randomised to a salmon fish protein supplement or placebo, and 74 participants were included in the analysis of vitamin D, omega-3, vitamin B12, selenium, folate, zinc, homocysteine and mercury. RESULTS: During the intervention period, geometric mean (GSD) of serum vitamin B12 concentrations increased from 304 (1.40) to 359 (1.42) pmol/L in the fish protein group (P vs. controls = 0.004) and mean (SD) serum selenium increased from 1.18 (0.22) to 1.30 (0.20) μmol/L (P vs. controls = 0.002). The prevalence of low vitamin B12 status (B12 < 148–221 > pmol/L) decreased from 15.4 to 2.6% in the fish protein group, while increasing from 5.9 to 17.6% in the placebo group (P = 0.045). There was no difference between the groups in serum levels of the other micronutrients measured. CONCLUSION: Including a salmon fish protein supplement in the daily diet for 8 weeks, increases serum vitamin B12 and selenium concentrations. From a sustainability perspective, by-products with high contents of micronutrients and low contents of contaminants, could be a valuable dietary supplement or food ingredient in populations with suboptimal intake. TRAIL REGISTRATION: The study was registered at ClinicalTrials.gov (ID: NCT03764423) on June 29th 2018.