When we were young, we were often told to eat our carrots to help our sight. Many a parent professed that rabbits don’t wear glasses, so carrots must be good for our eyes.
As silly as their hypotheses may seem, the reality is that there is something to the connection between carrots and vision: carotenoids.
Carotenoids are plant-based pigments found in many fruits and vegetables. They are powerful antioxidants and are frequently responsible for the bright, deep colors of most produce, such as yellow peppers, deep green spinach, and, yes, orange carrots.
Carotenoids and Vision
Of the more than 700 carotenoids found in nature, three in particular accumulate in the eye: lutein, zeaxanthin and meso-zeaxanthin. Specifically, they accumulate in the macula, which lies in the center of your retina and allows you to see fine details clearly. It is often referred to as the “sensitive center” of the retina.
Age-related impairment to the macula is known as age-related macular degeneration (or AMD), and is often the result of “photo oxidative-induced retinal injury.” That’s simply science-speak for light damage to the retina.
Given this commonly accepted cause of AMD, many researchers believe that the pigments in the retina, and in the macula specifically, may help protect the eye from AMD. Some even go so far as to question if these macular pigments actually play a role in the quality of vision.
But before either of those issues can be fully addressed, Irish researchers thought it best to determine if these pigments can be increased in the body, as well as in the macula itself through supplementation, and if this type of supplementation is safe and well tolerated.
Fortifying Your Eyes
Researchers divided 44 participants into two groups. One group received a placebo while the other group received a supplement containing 10.6 mg of meso-zeaxanthin, 5.9 mg of lutein, and 1.2 mg of zeaxanthin. Both groups took their capsule every day for six months.
All participants were tested for several vision-related markers at the start and end of the study, including:
- Best-corrected visual acuity (i.e., 20/20)
- Contract sensitivity
- Retinotopic ocular sensitivity
- Macular pigment optical density (this marker was retested at month three as well as baseline and end of the study)
Researchers also tested for several specific health markers at baseline and the study’s end to help determine the effectiveness and safety of using this particular carotenoid blend. To determine this, they tested:
- Blood carotenoid analysis of lutein and zeaxanthin (also taken at month three) [Editor’s note: The authors state that meso-zeaxanthin was not quantified separately, as meso-zeaxanthin response is detected as part of zeaxanthin peak.]
- Changes in Changes in kidney and liver function
- Cholesterol changes (LDL, HDL and triglycerides)
- Blood changes
At the conclusion of the study, only 35 of the original 44 participants successfully completed the study. Of these, 18 were in the carotenoid group and 17 were in the placebo group, so the results were still well balanced.
Of all the markers tested, researchers noted significant changes in just two areas: blood concentration of lutein and zeaxanthin, as well as a statistically significant increase in central macular pigment optical density (MPOD). Both areas saw increases at three and six months.
There was a 1.5-fold increase in lutein from baseline to conclusion and a 1.6-fold increase in zeaxanthin by study’s end. What was interesting about the changes in MPOD was that only central MPOD saw a significant increase due to supplementation. Researchers hypothesized that this may be because they used a meso-zeaxanthin dominant supplement, as meso-zeaxanthin tends to accumulate in the center of the macula.
On the pathology front, i.e., kidney and liver function, cholesterol, blood and inflammation, the supplementation appeared to have no effect on any of the markers tested.
Based on these results, researchers concluded that not only are meso-zeaxanthin, lutein and zeaxanthin safe with no signs of toxicity, but macular pigment may confer protection against macular degeneration. This makes the increase in blood and central MPOD important for people with or at risk for macular degeneration.
Get Those Greens… and Oranges…
Some of the best sources for both lutein and zeaxanthin can be found right in your grocery store. Load up on green leafy vegetables, red and green peppers, carrots, corn, tomatoes, broccoli and basically any brightly colored vegetable you lay your eyes on.
If you prefer the supplement route, studies have shown that you can take 20 mg of lutein a day for up to six months with no adverse effects. But you probably don’t need that much to have an effect. Follow this study’s dosages and look for a product with at least 6 mg of lutein and about 2 mg of zeaxanthin.
 Loane E, et al. The rationale and evidence base for a protective role of macular pigment in age-related maculopathy. Br J Ophthalmol. 2008;92:1,163-8.
 Loughman J, et al. Macular pigment and its contribution to visual performance and experience. J Optometry. 2010;3:74-90.
 Connolly, EE et al. Supplementation with all three macular carotenoids: response, stability and safety. Invest Ophthalmol Vis Sci. 2011 Oct 6. [Epub ahead of print.]
 Aleman TS, et al. Macular Pigment and Lutein Supplementation in Retinitis Pigmentosa and Usher Syndrome. Invest Ophthalmol Vis Sci. 2001;42:1,873-81.