British Journal of Nutrition

Research Article

Fasting plasma zeaxanthin response to Fructus barbarum L. (wolfberry; Kei Tze) in a food-based human supplementation trial

Chung Yuen Chenga1, Wai Yuen Chunga1, Yim Tong Szetoa1 and Iris F. F. Benziea1 c1

a1 Antioxidant Research Group, Faculty of Health & Social Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China


Age-related macular degeneration (AMD) is a common disorder that causes irreversible loss of central vision. Increased intake of foods containing zeaxanthin may be effective in preventing AMD because the macula accumulates zeaxanthin and lutein, oxygenated carotenoids with antioxidant and blue light-absorbing properties. Lycium barbarum L. is a small red berry known as Fructus lycii and wolfberry in the West, and Kei Tze and Gou Qi Zi in Asia. Wolfberry is rich in zeaxanthin dipalmitate, and is valued in Chinese culture for being good for vision. The aim of this study, which was a single-blinded, placebo-controlled, human intervention trial of parallel design, was to provide data on how fasting plasma zeaxanthin concentration changes as a result of dietary supplementation with whole wolfberries. Fasting blood was collected from healthy, consenting subjects; fourteen subjects took 15 g/d wolfberry (estimated to contain almost 3 mg zeaxanthin) for 28 d. Repeat fasting blood was collected on day 29. Age- and sex-matched controls (n 13) took no wolfberry. Responses in the two groups were compared using the Mann–Whitney test. After supplementation, plasma zeaxanthin increased 2·5-fold: mean values on day 1 and 29 were 0·038 (sem 0·003) and 0·096 (sem 0·009) μmol/l (P<0·01), respectively, for the supplementation group; and 0·038 (sem 0·003) and 0·043 (sem 0·003) μmol/l (P>0·05), respectively, for the control group. This human supplementation trial shows that zeaxanthin in whole wolfberries is bioavailable and that intake of a modest daily amount markedly increases fasting plasma zeaxanthin levels. These new data will support further study of dietary strategies to maintain macular pigment density.

(Received May 10 2004)

(Revised August 09 2004)

(Accepted September 01 2004)


c1 *Corresponding author: Professor Iris Benzie, fax +852 23649663, email