In the news: Lutein & Functional Vision: Carotenoids in Early AMD

Carotenoids, Functional Vision and AMD

AREDS 2 showed that lutein and zeaxanthin reduces the risk of developing advanced AMD, at least in those with low dietary intake. While it’s not yet known how these carotenoids might impact the disease process in early AMD, there is growing evidence that they may benefit visual performance.

Several past studies have reported that higher macular pigment optical density (MPOD) and lutein/zeaxanthin supplementation are related to improvements in glare disability, photo stress recovery, and chromatic contrast both in patients with early AMD and in healthy individuals (1,2).

Two studies related to these areas of investigation have recently been published. One study examines the effect of supplemental lutein on inflammation in early stage AMD. The other assesses the link between lutein/ zeaxanthin, MPOD, and measures of visual function in young adults via a randomized trial.

Lutein & Complement System in Early AMD

The complement system is an important player in the inflammatory process, and evidence suggests its activation contributes to AMD. Susceptibility genes encoding for complement factor H have been identified, and complement proteins have been found in drusen.

The present study (3), conducted by researchers from the Netherlands and the UK, is the first to explore whether lutein might affect complement activation.

Seventy patients with signs of early AMD randomly received a 10 mg daily dose of lutein or placebo for 1-year. Participants’ plasma levels of sC5b-9 (soluble complement membrane attack complex) were determined by ELISA at various time points. A marker of systemic inflammation, sC5b-9 is the final product of the 3 different complement activation pathways.

A significant monthly decrease of 1.1 ng/ml in plasma sC5b-9 was seen for the lutein group, resulting in an annual decline from an initial 60.3 ng/ml to 46.3 ng/ml at 1 year. In placebos, sC5b-9 went up 0.6 ng/ml monthly, with a yearly increase of 51.6 to 58.4 ng/ml.

The relative contribution of the 3 different complement pathways is not yet known in AMD patients, nor could the researchers pin down which of the pathways lutein affected. However the study provides evidence that lutein inhibits complement activation, and the authors conclude that lutein “can be considered as a potential prevention and treatment for AMD”.

Lutein & Zeaxanthin Improve Visual Function

Carotenoids can influence the optical characteristics of the eye, but can they impact vision in a meaningful way? University of Georgia researchers explored this question, measuring functional vision parameters in 115 healthy young adults randomized to receive 10 mg lutein and 2 mg zeaxanthin or placebo in a 1-year trial (4).

Results: Intent to treat analysis showed that MPOD increased significantly in the carotenoid group vs. placebo at all measured eccentricities (distances from the center of the macula). Chromatic contrast and photo stress recovery time improved significantly versus placebo. Glare disability was correlated with MPOD throughout the study period, but did not increase significantly in the treated group.

One limitation of the study was a high drop out rate, with 34 subjects withdrawing over the course of the year (largely students leaving the university). However, the findings are generally consistent with other randomized controlled trials, most of which report that increasing MPOD leads to better visual performance.

References

1. Huang Y-M, et al. Changes following supplementation with lutein and zeaxanthin in retinal function in eyes with early age-related macular degeneration: a randomized, double-blind, placebo-controlled trial Br J Ophthmol 99:371-5, 2015 [Epub Sept 16, 2014].
2. Stringham JM, et al. Macular pigment visual performance under glare conditions. Optom Vis Sci 85:82-8, 2008.
3. Tian Y, et al. Lutein supplementation leads to decreased souble complement membrane attack complex sC5b-9 plasma levels. Acta Ophthalmol 93:141-45, 2015.
4. Hammond BR, et al. A double-blind, placebo-controlled study on the effects of lutein and zeaxanthin on photo-stress recovery, glare disability and chromatic contrast. Invest Ophthalmol Vis Sci 55:8593-89, 2014.