Increased sodium content after saltwater washing did not compromise the attenuation of blood pressure increase by cod backbone proteins in obese Zucker fa/fa rats

Abstract A high sodium intake is a major risk factor for raised blood pressure. Consumption of fish fillet is associated with lower blood pressure in humans and other animals, whereas the effects of consuming fish residuals are less explored. To obtain high-quality fishmeal with acceptable sensory properties, the fish residuals may be washed with seawater onboard factory trawlers. This will increase the sodium content in the residuals, and whether this affects blood pressure has not yet been investigated. The primary objective of the present study was to investigate if the increased sodium content in Atlantic cod ( Gadus morhua ) residuals after washing with saltwater affected the development of high blood pressure in male obese Zucker fa/fa rats which spontaneously develop hypertension. Rats were fed diets containing cod protein powders prepared from unwashed or saltwater-washed backbone or head fractions ( n 6/group) as 25% of total protein with the remaining 75% as casein, or casein as the sole protein source (Control group, n 6) for six weeks. Blood pressure was measured on day 0 and 40. The diets containing backbone protein powder, independent of whether this fraction was washed with saltwater or not, attenuated the blood pressure increase compared to the Control group, whereas diets containing washed or unwashed head protein powder did not affect the blood pressure development. To conclude, a diet containing cod backbone protein powder attenuated the blood pressure increase in obese Zucker fa/fa rats, and this effect was not compromised by the higher sodium content in backbones washed with saltwater.