Vascular effects and safety of supplementation with shark liver oil in middle‑aged and elderly males

Shark liver oil (SLO) has long been used as a traditional health food, with a particular benefit for vascular health, in Japan. The aim of this study was to assess the effect of dietary supplementation with SLO on arterial stiffness and peripheral microvascular function in otherwise healthy middle-aged and older males with slightly increased arterial stiffness. A randomized, double-blind, placebo-controlled, parallel study design was used to assign 41 healthy males with a mean age of 59.0±4.0 years (range, 45–69 years) to either SLO (n=21) or placebo (n=20) treatment for eight weeks. The effects on arterial stiffness and peripheral microvascular function were assessed by the cardio-ankle vascular index (CAVI) and by measurement of hand blood flow to cutaneous tissues using a laser Doppler perfusion imaging (LDPI) technique, respectively. Although the magnitude of the changes in the CAVI value during the eight-week intervention for the SLO group did not significantly differ from that for the placebo group, the changes in the CAVI value for the former group were significantly associated (r=0.575, P<0.01) with age. It was also found that the LDPI values at week 8 were significantly lowered (P<0.05) compared with the baseline values in the placebo group, while no change was observed in the SLO group, resulting in a significant difference in the changes between the two groups (P=0.002). Neither SLO supplementation-related adverse side-effects nor any abnormal changes in routine laboratory tests, including lipid profiles and anthropometric and haemodynamic parameters, were observed throughout the intervention. SLO may have the potential to safely improve vascular health in middle-aged and elderly males.