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| Date: 06-30-2015 | HC# 061561-523 |
Re: Effect of Lutein and Zeaxanthin on Retinal Function in Patients with Macular Degeneration
Huang YM, Dou HL, Huang FF, et al. Changes following supplementation with lutein and zeaxanthin in retinal function in eyes with early age-related macular degeneration: a randomised, double-blind, placebo-controlled trial. Br J Ophthalmol. March 2015;99(3):371-375.
Age-related macular degeneration (AMD) is a progressive retinal eye disease resulting in loss of vision, typically later in life. Both inflammation and hypoxia (insufficient oxygen) have been associated with AMD via secondary oxidant damage. The decrease of macular pigment optical density (MPOD) has also been linked to the oxidant harm correlated with AMD progression, as the macular pigments are composed of the antioxidant compounds lutein, zeaxanthin, and meso-zeaxanthin. However, trials with carotenoid supplementation are conflicted. Timing of the intervention in AMD etiology may be important, thus, this randomized, double-blind, placebo-controlled trial investigated lutein and zeaxanthin intake on MPOD and sensitivity of the retina in patients with AMD.
This trial was conducted in Beijing, China and enrolled 112 patients diagnosed with early AMD. Patients were more than 50 years old and had clear ocular media. Those with other eye problems or diseases, or who had taken carotenoid-containing supplements 6 months prior to the study, were excluded. Included patients were randomly assigned to consume 10 mg of lutein, 20 mg of lutein, a combination of 10 mg of lutein together with 10 mg of zeaxanthin, or a placebo treatment taken every day for 2 years. Sources of compounds and contents of placebo were not described.
At baseline, demographic information, food consumption, and MPOD were assessed. MPOD continued to be measured after 24 and 48 weeks and after 2 years. The sensitivity of the retina was assessed by multifocal electroretinogram (mfERG, a measurement of retinal cell function, divided here into 6 circular ring areas of measurement) at baseline and again at 48 weeks. Mean retinal sensitivity (MRS) was measured at 48 weeks and 2 years. Treatments were distributed monthly, and compliance was monitored at these times. Patients kept their normal routines and mentioned any adverse side effects.
Following the initial screening, 112 patients were enrolled in this study. Of these, 4 patients did not attend the clinical visits and were dropped from the study, leaving 108 in the final analysis. There were no significant differences in parameters at baseline, including carotenoid consumption. Following the treatment, MPOD significantly increased after 24 weeks (P<0.01), 48 weeks (P<0.001), and 2 years (P<0.001) in the 20 mg lutein group as compared to baseline. In the 10 mg lutein group, increased MPOD was observed after 2 years (P<0.001) as compared to baseline. This was also seen after 48 weeks and 2 years (P<0.05 for both) in the group taking both lutein and zeaxanthin.
N1P1 response density (data from mfERG measurement defined as amplitude per unit of retinal area) for ring 1 significantly increased in all carotenoid treatment groups as compared to baseline (P<0.05 for all). In the lutein plus zeaxanthin group, this increase was significantly greater than baseline values and in comparison to placebo at both baseline and 48 weeks (P<0.01 for both). For ring 2, those in the 20 mg lutein group had significantly increased N1P1 response density as compared to baseline (P<0.05). Also, there was a significant time effect on elevated N1P1 response density for rings 1 and 2 (P≤0.02 for both) and a treatment effect on changes in ring 1 that approached significance (P=0.06). No changes were seen in the placebo group. At 48 weeks, MRS intensities at 3° eccentricity (a term of distance measurement) in all groups and 5° eccentricity in the 20 mg lutein and lutein plus zeaxanthin groups were significantly increased as compared to the placebo group (P<0.05 for all). After 2 years of treatment, those taking 10 mg of lutein and 20 mg of lutein had a significantly increased MRS intensity at 1° eccentricity as compared to the placebo group (P<0.01 and P<0.05, respectively). No adverse side effects were noted.
Overall, this study reports significant improvements in MPOD, N1P1 response density, and MRS after 2 years of lutein and zeaxanthin supplementation in patients suffering from AMD, all indicative of visual function improvement. It is suggested that decreased MPOD is a possible risk factor for AMD, and that increased MPOD may alleviate AMD. One mechanism mentioned for the increase in MPOD in all treatment groups is the contribution of lutein to meso-zeaxanthin concentration in the retina. Also discussed is the potential antioxidant activity of the supplemented compounds. Suggested limitations of this study include a lack of a meso-zeaxanthin treatment group and limited study duration. Regardless, future studies on the preventative effects of carotenoid intake on AMD progression are warranted.
—Amy C. Keller, PhD
