Systematic Review of Lutein and Zeaxanthin and the Maintenance of Vision

  • Organisation Food & Nutrition Australia, Westmead Hospital, Western Sydney Local Health District and The University of Sydney
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Systematic Review of Lutein and Zeaxanthin and the Maintenance of Vision

Lutein and Zeaxanthin Eye Health

The objective of this systematic review was to assess whether dietary intake of lutein and zeaxanthin (L/Z) helps maintain vision in adults.
Lutein and zeaxanthin, are xanthophyll carotenoids naturally present in food, especially in dark green leafy vegetables, such as spinach and kale, as well as eggs – in the egg yolk. Eggs have been found to be a particularly bioavailable source of these carotenoids.

With their isomer meso-zeaxanthin, L/Z accumulate in the macula, the central part of the retina responsible for fine detail and central vision. Given their high concentration in this area of the body, research has investigated their potential role in eye health and vision.

A literature review was conducted in the PubMed and CINAHL databases, in May 2018, limited to human cohort and randomised controlled trials. Manual searches were also performed on the reviewed full text papers from the original search. Relevant medical subject heading (MeSH) terms and keywords included: lutein, zeaxanthin, xanthophyll/s, antioxidant/s or carotenoid/s in conjunction with the following: vision, visual performance, visual function, visual acuity, contrast sensitivity, age-related macular degeneration, age-related maculopathy. The main outcomes were measures of vision including visual acuity, contrast sensitivity and age-related macular degeneration (incidence and progression). This review was not concerned with studies in which participants had pre-existing eye disease (other than AMD) including cataracts, retinitis pigmentosa and diabetic retinopathy.

Using the inclusion and exclusion criteria the 762 publications from the original search were reduced to 16 included studies. These 16 studies were 8 cohort studies and 8 randomised controlled trials (RCTs). The cohort studies investigated the relationship between dietary L/Z intake and incidence and/or progression of age-related macular degeneration (AMD) in populations including Blue Mountains Eye Study (BMES) cohort, the Rotterdam cohort, the Nurses Health Study (NHS) cohort, the Health Professionals Follow Up Study (HPFS) cohort and the Atherosclerosis Risk in Community (ARIC) cohort. All cohort studies rated as high quality using the Health Canada Quality Appraisal tool.

The 8 RCTs investigated the effect of supplemental L/Z on AMD progression and/or measures of vision including visual acuity and contrast sensitivity. All RCTs rated as high quality using the Health Canada Quality Appraisal tool.

Cohort studies did not consistently find a statistically significant favourable effect of L/Z intake on early AMD, however when analysis was isolated to individuals at high genetic risk of AMD a 22% reduction in risk was found in the highest levels of intake. High quality cohort studies inconsistently found a favourable effect of L/Z intake on intermediate and advanced AMD – the types of AMD most likely to result in vision loss. In a study investigating genetic risk as an effect modifier, the highest tertile intakes of L/Z were non-significantly associated with an approximately 35% risk reduction in advanced AMD while there was a significant reduced risk of any AMD. Cohort studies may have been subject to residual confounding and/or difficulties in quantifying L/Z intake biasing their findings towards the null.

The AREDS2 RCT found individuals with a background dietary L/Z intake of <1428μg/day benefitted for the 12mg L/Z supplement (HR of 0.74 (95% CI, 0.59-0.94, p=0.01)). Other RCTs included in the systematic review consistently showed L/Z supplementation enhanced contrast sensitivity and visual acuity (although VA results did not always reach statistical significance).

The relationship between L/Z and vision is biologically plausible. Evidence demonstrates the macular pigment has blue light-filtering properties as well as anti-oxidant and possibly anti-inflammatory actions.

Overall, while results from observational cohort studies to date have been inconsistent, the evidence from high quality intervention studies on late AMD and visual performance including contrast sensitivity and visual acuity consistently show favourable effects of L/Z on these health effects suggesting a causal effect. Furthermore, the relationship between L/Z and maintenance of vision has high biological plausibility and levels of intake are possible in the current Australian and New Zealand food environment.

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