Antioxidants and Eye Health

Antioxidants are protectants, like bodyguards for your cells and their interior parts, including DNA. We have systems in place all over the body stationing these antioxidants to prevent the body’s tissues from getting damaged from what is called oxidative stress. As part of our normal metabolism, we create molecules called free radicals. These free radicals are highly reactive molecules and in small amounts they can actually do us a few favours, but in larger concentrations they can cause havoc, leading to oxidative cell damage and inflammation.

Because we collect free radicals from sources other than the body’s regular metabolism, such as from the foods we eat, the air we breathe (air pollution), infections, chemicals and environmental exposures, it’s important that your body can handle these situations. In order to do so, we need the help of antioxidants to “neutralize” free radicals and prevent oxidative stress and damage. We can do this either by consuming antioxidant-rich plant-based foods like fruits and vegetables, or with antioxidant supplements.

The eyes are a very interesting organ since the majority of their oxidative stress comes from light exposure. The tissues in the front of the eye, such as the cornea and lens, take on the majority of this stress as they are constantly exposed to huge amounts of UV radiation. To compensate for this, the body concentrates ascorbic acid (vitamin C) in the cells of the cornea to help protect this tissue from oxidative stress.¹

Meanwhile, the lens and other ocular cells also have access to antioxidants and a means of recycling them to help their defences. But as we age, the amount and actions of our natural antioxidants declines, making diet and supplementation even more important.

There are multiple antioxidants that are specific to eye heath including vitamin C, lutein, zeaxanthin and N-acetyl cysteine (NAC) and/or glutathione.

Carotenoids and Eye Protection

Carotenoids are a type of antioxidant that help protect the retina and the macula, areas at the back of the eye that absorb light and are responsible for vision, from light damage.²

Carotenoids in the macula, a small focused area of the retina, in particular absorb 40% to 90% of blue light, and therefore are in major need of protection.³ This is where lutein and zeaxanthin come in. These two carotenoids are responsible for increasing the retina’s macular pigment, which protects different areas of the retina from extremely damaging blue light. Macular pigment therefore acts like a sunscreen for your eyes, helping you preserve your vision.

What’s interesting is that having greater amounts of macular pigment can reduce the impact of bright light exposure on the eyes, shortening the time needed to recover after intense exposure.³ Supplementing with lutein and zeaxanthin has been shown to improve macular pigment in those with healthy eyes, and in those who have age-related macular degeneration (AMD).⁴

AMD happens when little fatty deposits accumulate right under the cells of retina pigment. These deposits are called drusen and they look like yellow spots on the retina (that’s what your eye doctor will see). Having drusen disrupts the pigment distribution, making some areas well protected, but other areas sparse. This can cause the retinal pigment cells to die off and can lead to major vision loss.⁵

Lutein is found in leafy green vegetables such as spinach and chard, and by consuming these foods, it provides protection, helping decrease the risk of developing cataracts and vision loss. Supplementing with 20 mg per day has been shown to prevent and improve both AMD and cataracts.²

In one trial, supplementing adults aged 18 to 32 years with zeaxanthin either alone or with lutein and omega-3 fatty acids led to increased macular pigment density.³ This led to significant improvements in visual processing speed.

In another study, the use of lutein (10 mg or 20 mg) and zeaxanthin (10 mg) for patients with early AMD for two years significantly increased macular pigment density, and some forms of visual function.⁶

Glutathione and NAC

Glutathione is a major antioxidant in the body. Its precursor molecule is NAC, another antioxidant. NAC is interesting for eye health because it can get through cell membranes and bypass the need for specific transporter molecules. Supplementing with NAC or glutathione could benefit vision during aging since glutathione is involved in maintaining the barrier function of the cells of the cornea, while keeping the eye’s hydration levels normal, and protecting all the surrounding cells.

Vitamin C

Like with most antioxidants in the body, vitamin C levels in the eye decrease with aging and is associated with greater severities of cataracts.⁷ Consuming food sources or supplemental vitamin C therefore could help protect against cataract formation during natural aging.⁷ However, the current evidence isn’t conclusive that vitamin C supplementation prevents or slows the progression of AMD.

Overall, specific antioxidants such as lutein, zeaxanthin, and NAC can be helpful for protecting the eyes from light damage. This could help preserve vision during aging and for those who are exposed to great amounts of blue light such as those with extensive computer/screen use.

References

1. Umapathy A, Donaldson P, Lim J. (2013). Antioxidant delivery pathways in the anterior eye. Biomed Res Int. 2013:207250

2. Buscemi S, Corleo D, Di Pace F, et al. (2018). The effect of lutein on eye and extra-eye health. Nutrients. 10(9): 1321

3. Mares J. (2016). Lutein and Zeaxanthin Isomers in Eye Health and Disease. Annu Rev Nutr. 36:571-602

4. Ma L, Liu R, Du JH, et al. (2016). Lutein, Zeaxanthin and Meso-zeaxanthin Supplementation Associated with Macular Pigment Optical Density. Nutrients. 2016 Jul 12;8(7):426

5. Evans JR, Lawrenson JG. (2017). Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Syst Rev. 7(7):CD000254

6. Huang YM, Dou HL, Huang FF, et al. (2015). Effect of supplemental lutein and zeaxanthin on serum, macular pigmentation, and visual performance in patients with early age-related macular degeneration. Biomed Res Int. 2015:564738

7. Lim JC, Caballero Arredondo M, Braakhuis AJ, Donaldson PJ. (2020). Vitamin C and the Lens: New Insights into Delaying the Onset of Cataract. Nutrients. 12(10):3142