Improved process technologies have allowed fishing vessels to utilize residuals from cod fillet production (head, backbone, skin, cuttings, and entrails) and convert this to high-quality protein powders for human consumption. In this double-blind pilot study, 42 healthy overweight or obese adults were randomized to three experimental groups consuming tablets corresponding to 6 g/day of proteins from cod residuals as presscake meal (Cod-PC), presscake and stickwater meal (Cod-PCW), or placebo tablets (control) for eight weeks. The primary outcome of this study was changes in metabolites related to glucose regulation in overweight or obese healthy adults after intake of proteins from cod residuals. Cod-PC supplementation decreased postprandial serum nonesterified fatty acids (NEFA) concentration and increased gene expressions of diglyceride acyltransferase 1 and 2 in subcutaneous adipose tissue compared with controls. Fasting insulin increased while fasting NEFA and 120-min postprandial glucose decreased within the Cod-PC group, but these changes did not differ from the other groups. In conclusion, supplementation with Cod-PC beneficially affected postprandial serum NEFA concentration compared with the other groups in overweight or obese adults. Supplementation with Cod-PCW, which contains a higher fraction of water-soluble protein compared to Cod-PC, did not affect serum markers of glucose regulation.

Hypertension is the leading risk factor for cardiovascular disease, and prevention of high blood pressure through diet and lifestyle should be a preferred approach. High intake of fish is associated with lower blood pressure, possibly mediated through the proteins since peptides with angiotensin-converting enzyme (ACE) inhibiting capacities have been identified in fish skin, backbone, and fillet. The effects of cod meals made from residual materials and fillet on blood pressure were investigated in obese Zucker fa/fa rats which spontaneously develop high blood pressure. Rats were fed diets containing water-soluble (stickwater) or water-insoluble (presscake) fractions of protein-rich meals from cod residual materials (head, gut, backbone with muscle residuals, skin, trimmings) or fillet. Rats were fed diets containing 25% of total protein from cod meal and 75% of protein from casein, or casein as the sole protein source (control group) for four weeks. Results show that a diet containing residual presscake meal with high gut content prevented blood pressure increase, and this cod residual meal also showed the strongest in vitro inhibitions of ACE and renin activities. In conclusion, a diet containing water-insoluble proteins (presscake meal) with high gut content prevented increase in blood pressure in obese Zucker fa/fa rats.

BackgroundFish fillet consumption is associated with beneficial health effects; however, little is known about whether consuming other parts of the fish such as head, backbone, skin, cut-offs, and entrails (collectively known as residuals) will provide comparable effects.ObjectiveThe aim of the study was to investigate if daily supplementation with cod residual protein powder would impact lipid metabolism in healthy adults.MethodsForty healthy, lean, physically active participants (18 women, 22 men) with normal body mass index consumed 8.1 g of proteins daily from cod residual protein powder (Cod-RP) or placebo (control) for 8 weeks.ResultsCod residual protein powder supplementation lowered fasting serum nonesterified fatty acids and increased serum total bile acid concentrations significantly when compared with control supplementation. Fasting serum low-density lipoprotein cholesterol and apolipoprotein (Apo) B concentrations, as well as the total cholesterol:high-density lipoprotein (HDL) cholesterol and ApoB:ApoA1 ratios, were significantly decreased within the Cod-RP group, but these changes were not different from the control group. Fasting serum concentrations of triacylglycerol, total cholesterol, HDL cholesterol, and ApoA1 were not changed within or between groups.ConclusionEight weeks of daily supplementation with 8.1 g Cod-RP seems to be sufficient to affect lipid metabolism in healthy, lean, physically active adults.

Large quantities of protein-rich cod residuals, which are currently discarded, could be utilized for human consumption. Although fish fillet intake is related to beneficial health effects, little is known about the potential health effects of consuming cod residual protein powder. Fifty lean adults were randomized to consume capsules with 8.1 g/day of cod residual protein (Cod-RP) or placebo capsules (Control group) for eight weeks, in this randomized, double-blind study. The intervention was completed by 40 participants. Fasting glucose and insulin concentrations were unaffected by Cod-RP supplementation, whereas plasma concentrations of α-hydroxybutyrate, β-hydroxybutyrate and acetoacetate all were decreased compared with the Control group. Trimethylamine N-oxide concentration in plasma and urine were increased in the Cod-RP group compared with the Control group. To conclude, the reduction in these potential early markers of impaired glucose metabolism following Cod-RP supplementation may indicate beneficial glucoregulatory effects of cod residual proteins. Trimethylamine N-oxide appears to be an appropriate biomarker of cod residual protein intake in lean adults.

Background: Documentation of health effects of residuals after fish filleting may motivate both consumers and producers to increase the use of this under-utilised protein source. Objectives: The primary objective of the present study was to investigate the effects of a diet containing residuals from Atlantic cod (Gadus morhua) filleting on the development of high blood pressure in obese Zucker fa/fa rats, which spontaneously develop hypertension and proteinuria. The secondary objectives were to investigate any changes in kidney morphology, kidney function and organ damage, and to determine the potential inhibition of cod residuals on renin and angiotensin-converting enzyme (ACE) activities in vitro. Methods: Male rats were fed diets containing protein powder prepared from head, backbone and skin fraction (HBS, n = 6) from Atlantic cod as 25% of total protein with the remaining 75% as casein, or casein as the sole protein source (Control group, n = 6) for 4 weeks. Blood pressure was measured on day 0, 14 and 26. Kidneys were analysed morphologically, and markers for renal function and organ damage were analysed biochemically. Results: The HBS diet attenuated the blood pressure increase compared to the Control group, but kidney damage and dysfunction were similar between the two groups. Conclusion: A diet containing a protein powder consisting of HBS fraction from cod attenuated the blood pressure increase in obese Zucker fa/fa rats, without preventing kidney damage.