Human Studies

Of note, MZ is a regular dietary component in countries where it is a major pigment used by the poultry industry, particularly Mexico, and no adverse effects have been reported. In addition, the safety of MZ has been tested in human clinical trials.

The first study to evaluate the effects of a dietary supplement containing predominantly MZ was conducted in a Miami research laboratory. This research confirmed that MZ was effectively absorbed into the serum, and macular pigment density was increased significantly in many subjects in the supplementation group. No such increases were observed in the placebo group.

In another study done in Northern Ireland, 19 subjects consumed a supplement also composed of all three macular carotenoids, including MZ over a period of 22 days. Results demonstrated that MZ was absorbed. At the Institute of Vision Research, Waterford Institute of Technology, the MZ Ocular Supplementation Trial (MOST), was conducted to evaluate macular pigment response and serum carotenoid response in subjects with and without AMD, following consumption of a supplement containing all three macular carotenoids in which MZ was predominant. This study identified statistically significant increases in serum concentrations of MZ and L from baseline. Significant increases in central macular pigment levels were also observed after just two weeks of supplementation. Furthermore, in patients who had an atypical macular pigment distribution in the eye (i.e. they did not have the high concentration of pigment in the centre of the macula), when supplemented with a MZ-dominant supplement for 8 weeks, the more normal pigment profile was re-instated.

The main findings from the MOST trials in patients with AMD have been published in 2014 and the final report is due in 2015. This publication by Sabour-Pickett concluded “Augmentation of the macular pigment optical density across its spatial profile and enhancements in contrast sensitivity were best achieved after supplementation with a formulation containing high doses of meso-zeaxanthin in combination with lutein and zeaxanthin.”

In 2016 and 2017, two major clinical trials were published in the international journal, Investigative Ophthalmology & Visual Science (IOVS). These studies were funded by the European Research Council (Ref: 281096).  The first trial, the CREST (Central Retinal Enrichment Supplementation Trials) normal study involved 105 volunteers who underwent a series of complex tests of vision and were supplemented over a 12-month period. Of the 105 subjects, 53 received daily active supplements containing meso-zeaxanthin, lutein and zeaxanthin, while 52 subjects received a placebo (the control group). The outcome unequivocally demonstrates that those receiving macular carotenoids – lutein, zeaxanthin and meso-zeaxanthin – enjoyed meaningful benefits to their visual function. The improvement recorded was primarily in people’s contrast sensitivity – how much contrast a person needs to see a target (i.e. how faint an object can you see).This work demonstrates important implications for those who rely on their vision for professional reasons, such as high-performance sportspeople (most obviously golfers, cricketers, tennis and baseball players), motorists, train drivers, pilots, and police. (Nolan et al., 2016).

The second trial, CREST AMD was a major two-year trial involving over 100 people diagnosed with the early stages of AMD, and has shown an improvement in the vision of those taking a dietary supplement of carotenoids. Those living with AMD would usually have been expected to experience a continued deterioration in their vision over the two years of the clinical trial. Instead, those receiving carotenoids showed a significant improvement across 24 out of 32 tests of vision. 35% of trial participants had what is deemed to be a clinically meaningful improvement in their vision after 24 months, but only in the active supplement containing meso-zeaxanthin. Improvements in vision were particularly marked among those receiving all three carotenoids compared to those receiving only zeaxanthin and lutein. The research was conducted by a team from the Nutrition Research Centre Ireland (NRCI) at Waterford Institute of Technology (WIT). (Akuffo et al., 2017)

All publications from the meso-zeaxanthin (MOST) studies are summarised presented below and available on our publication section.


(1)  Connolly EE, Beatty S, Thurnham DI, Loughman J, Howard AN, Stack J, et al. Augmentation of macular pigment following supplementation with all three macular carotenoids: an exploratory study. Curr Eye Res 2010 Apr;35(4):335-51.

(2)  Connolly EE, Beatty S, Loughman J, Howard AN, Louw MS, Nolan JM. Supplementation with all three macular carotenoids: response, stability, and safety. Invest Ophthalmol Vis Sci 2011 Nov 29;52(12):9207-17.

(3)  Meagher KA, Thurnham DI, Beatty S, Howard AN, Connolly E, Cummins W, et al. Serum response to supplemental macular carotenoids in subjects with and without age-related macular degeneration. Br J Nutr 2013 Dec 5;110(2):289-300.

(4)  Nolan JM, Akkali MC, Loughman J, Howard AN, Beatty S. Macular carotenoid supplementation in subjects with atypical spatial profiles of macular pigment. Exp Eye Res 2012 May 28;101:9-15.

(5)  Loughman J, Nolan JM, Howard AN, Connolly E, Meagher K, Beatty S. The impact of macular pigment augmentation on visual performance using different carotenoid formulations. Invest Ophthalmol Vis Sci 2012 Nov 6;53:7871-80.

(6)  Thurnham DI, Nolan JM, Howard AN, Beatty S. Macular response to supplementation with differing xanthophyll formulations in subjects with and without age-related macular degeneration. Graefes Arch Clin Exp Ophthalmol 2014 Oct 14.

(7)  Sabour-Pickett S, Beatty S, Connolly E, Loughman J, Stack J, Howard A, et al. Supplementation with three different macular carotenoid formulations in patients with early age-related macular degeneration. Retina 2014 May 30;34:1757-66.

(8) NOLAN, J. M., POWER, R., STRINGHAM, J., DENNISON, J., STACK, J., KELLY, D., MORAN, R., AKUFFO, K. O., CORCORAN, L. & BEATTY, S. 2016. Enrichment of Macular Pigment Enhances Contrast Sensitivity in Subjects Free of Retinal Disease: Central Retinal Enrichment Supplementation Trials – Report 1Central Retinal Enrichment Supplementation Trials. Investigative Ophthalmology & Visual Science, 57, 3429-343.

(9) AKUFFO, K. O., BEATTY, S., PETO, T., STACK, J., STRINGHAM, J. M., KELLY, D., LEUNG, I., CORCORAN, L. & NOLAN, J. M. 2017. The impact of supplemental antioxidants on visual function in non-advanced age-related macular degeneration: a head-to-head randomized clinical trial. Invest Ophthalmol. Vis. Sci.