Re: lutein supplementation improves visual performance in Chinese drivers: 1-year randomized, double-blind, placebo-controlled study: the importance of supplementing with all three macular carotenoids.

To the Editor: We congratulate Yao et al [1] on their valuable contribution to the area of nutritional supplementation to maximize visual performance. In brief, Yao et al conducted a randomized, double-blind, placebo-controlled trial of patients supplemented with 20mg of lutein daily versus placebo, and found that supplementation with 20 mg of lutein per day resulted in improvements in terms of contrast sensitivity and glare disability, especially under mesopic conditions. Indeed, the findings of Yao et al are consistent with the growing evidence base in this area, which indicates that high levels of macular pigment are required for visual excellence in normal individuals [2]. Macular pigment is made up of three carotenoids, lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ), MZ being the dominant carotenoid at the visual center, where visual performance and sensitivity is maximal [3]. A recent randomized, placebocontrolled trial of differing carotenoid formulations versus placebo (also in normal participants), revealed that a formulation containing MZ resulted in the greatest improvements in visual performance (contrast sensitivity, under mesopic and photopic conditions, under and not under conditions of glare), whereas only minimal benefits were noted with the supplementation lacking the centrally dominant carotenoid (MZ); no visual improvements were noted in participants who were supplemented with placebos [4]. The finding that MZ is required in a formulation to maximally improve visual performance is unsurprising, given that 12% of the population has a central dip in the spatial profile of their macular pigment [5], and that in these individuals the normal, centrally peaked spatial profile of macular pigment can only be realized following supplementation with a formulation that contains all three of macular pigment’s constituent carotenoids (MZ, L, andZ in a ratioof 10:10:2) [6]. Also, thenecessityofMZ in a formulation to maximally enhance visual performance is consistent with a recent serum study, where it was shown that a preparation containing all three macular carotenoids was required if serum bioavailability of macular pigment’s constituent carotenoids was to bemaximized, and therefore enhance capture by the target tissue (macula) of these circulating compounds [7]. In summary, and again, we congratulate Yao et al for their excellent piece of work and contribution to this growing area of research. However, we believe that a formulation designed to optimize visual performance should include all three of macular pigment’s constituent carotenoids in a MZ:L:Z ratio of 10:10:2.