Supplementation with Seabuckthorn Oil Augmented in 16:1n-7t Increases Serum Trans-Palmitoleic Acid in Metabolically Healthy Adults: A Randomized Crossover Dose-Escalation Study

Abstract

In animal models cis-palmitoleic acid (9-hexadecenoic acid; 16:1n-7c), a lipokine, improves insulin sensitivity, inflammation, and lipoprotein profiles; in humans trans-palmitoleic acid (16:1n-7t) has been associated with lower incidence of type 2 diabetes. The response to dose-escalation of supplements containing cis- and trans-palmitoleic acid has not been evaluated. Objectives: We examined dose-escalation effects of oral supplementation with seabuckthorn oil and seabuckthorn oil augmented in 16:1n-7t on serum phospholipid fatty acids (PLFAs). Methods: Thirteen participants (7 women and 6 men; age 48 ± 16 y, BMI 30.4 ± 3.7 kg/m2) participated in a randomized, double-blind, crossover, dose-escalation trial of unmodified seabuckthorn oils relatively high in 16:1n-7c (380, 760, and 1520 mg 16:1n-7c/d) and seabuckthorn oils augmented in 16:1n-7t (120, 240, and 480 mg 16:1n-7t/d). Each of the 3 escalation doses was provided for 3 wk, with a 4-wk washout period between the 2 supplements. At the end of each dose period, fasting blood samples were used to determine the primary outcomes (serum concentrations of the PLFAs 16:1n-7t and 16:1n-7c) and the secondary outcomes (glucose homeostasis, serum lipids, and clinical measures). Trends across doses were evaluated using linear regression. Results: Compared with baseline, supplementation with seabuckthorn oil augmented in 16:1n-7t increased phospholipid 16:1n-7t by 26.6% at the highest dose (P = 0.0343). Supplementation with unmodified seabuckthorn oil resulted in a positive trend across the dose-escalations (P-trend = 0.0199). No significant effects of either supplement were identified on blood glucose, insulin, lipids, or other clinical measures, although this dosing study was not powered to detect such effects. No carryover or adverse effects were observed. Conclusions: Supplementation with seabuckthorn oil augmented in 16:1n-7t and unmodified seabuckthorn oil moderately increased concentrations of their corresponding PLFAs in metabolically healthy adults, supporting the use of supplementation with these fatty acids to test potential clinical effects in humans. This trial was registered at clinicaltrials.gov as NCT02311790.