Enhanced bioavailability of zeaxanthin in a milk-based formulation of wolfberry (Gou Qi Zi; Fructus barbarum L.)

Abstract

The carotenoid zeaxanthin is concentrated within the macula. Increased macular zeaxanthin is suggested to lower the risk of age-related macular degeneration. The small red berry, wolfberry (Fructus barbarum L.; Gou Qi Zi and Kei Tze), is one of the richest natural sources of zeaxanthin. However, carotenoid bioavailability is low, and food-based products with enhanced bioavailability are of interest. The present study investigated zeaxanthin bioavailability from three wolfberry formulations. Berries were homogenised in hot (80°C) water, warm (40°C) skimmed milk and hot (80°C) skimmed milk, with freeze drying of each preparation into a powdered form. A zeaxanthin-standardised dose (15mg) of each was consumed, in randomised order, together with a standardised breakfast by twelve healthy, consenting subjects in a cross-over trial, with a 3–5-week washout period between treatments. Blood samples were taken via a venous cannula immediately before (fasting) and 2, 4, 6, 7, 8 and 10h post-ingestion. Zeaxanthin concentration in the triacylglycerol-rich lipoprotein fraction of plasma was measured by HPLC. Results showed that triacylglycerol-rich lipoprotein zeaxanthin peaked at 6h post-ingestion for all formulations. Zeaxanthin bioavailability from the hot milk formulation was significantly higher (p<0·001) than from the others. Mean area under the curve (n 12) results were 9·73 (sem 2·45), 3·24 (sem 0·72) and 3·14 (sem 1·09) nmol×h/l for the hot milk, warm milk and hot water formulations, respectively. Results showed clearly that homogenisation of wolfberry in hot skimmed milk results in a formulation that has a 3-fold enhanced bioavailability of zeaxanthin compared with both the ‘classical’ hot water and warm skimmed milk treatment of the berries.