Although we use numerous senses to perceive our environment – sight, sound, smell, taste, touch – the largest portion of the brain is dedicated to processing visual cues. Of the millions of receptors in the body, it is estimated that 70 percent are involved with sight (photoreceptors) – so protecting the health of your eyes is of utmost importance.

Oxidative stress and the eye

Oxidative stress appears to be at the center of many eye conditions. What is oxidative stress? Oxidative stress results when there is an imbalance between pro-oxidants and antioxidants. If the body is exposed to too many oxidative insults without a counterbalance provided by antioxidants, then an excess of free radicals is produced, and cell damage can ensue – including in the eyes.

In the eye, rods and cones are two types of photoreceptors – nerve cells in the retina at the back of the eyeball. Rods are involved with peripheral vision and the ability to see in dim light, while cones are necessary for color vision and visual acuity.

These photoreceptors are nerve cells that, like other cells, contain fatty acids in their cell membranes, which makes them susceptible to oxidation. Combine this susceptibility with the fact that these cells are very metabolically active and are susceptible to damage by UV light from the sun, high-energy visible blue light (emitted by tv, computer, tablet, and cell phone screens), cigarette smoke, and other environmental insults, and you can have a perfect storm of oxidative stress. 

The eye’s photoreceptor cells are partially protected by neighboring cells in the retina called the pigmented epithelial layer – part of their job is to protect the photo receptors from UV light. UV light, however, can also contribute to oxidative stress in the pigmented epithelial cells in the retina. Outside the retina, UV light can cause changes to the proteins in the lens of the eye that can result in the lens becoming opaque.

Therefore, it should come as no surprise that oxidative stress is implicated in several conditions of the aging eye, including macular degeneration and retinopathy (both retinal issues), and cataracts in the lens of the eye.

In addition to protecting your eyes from environmental insults with proper sunglasses and blue-light filters, the eyes can benefit from certain dietary components or specific nutritional supplements.

Vitamin A and beta-carotene

The importance of vitamin A to eye heath cannot be overemphasized. It is an essential component of the pigments in the rods (rhodopsin) and cones (iodopsin). It’s not a coincidence that “retinol” and “retinal” are other names for forms of vitamin A. Outside the retina, vitamin A is also necessary for proper lubrication of the cornea. Thus, signs of a deficiency (uncommon in the U.S. but common in the developing world) include poor night vision and corneal ulceration that can lead to blindness. 

Carotenoids are pigments found in many plants. Probably the most well-known carotenoid is beta-carotene, and the most well-known source of beta-carotene is the mighty carrot. Beta-carotene is converted in the body to vitamin A. In addition to its conversion to vitamin A, beta-carotene on its own is an antioxidant that can benefit eye health.*

Good food sources of vitamin A include liver, eggs, and fish. In addition, in the United States, dairy products and cereals are often fortified with vitamin A. Beta-carotene is found in plant foods – sweet potatoes, pumpkin, carrots, and leafy greens being the best sources. Cooking and juicing foods like carrots make the beta-carotene more bioavailable.

Lutein and zeaxanthin

Carrots also contain other carotenoids that have been the subject of considerable study for eye health – lutein and zeaxanthin. Although these carotenoid pigments do not convert to vitamin A, they have important functions in the body. Their most direct function is to protect an area at the back of the eye called the macula, which sits in the middle of the retina. The macula is important for helping you see what is directly in front of you, allows you to see fine detail, and plays an important role in color vision. The macula can begin to degenerate with age.

The macula is the area of the eye most sensitive to oxidative damage by light. What do lutein and zeaxanthin do? They normally collect in the macula, increase its “optical density,” and protect it from damaging light rays, including from sunlight and blue-spectrum light.* Because these carotenoids are orange-yellow pigments, the normal color of the macula is orange-yellow. And, in fact, the full name of the macula is the macula lutea (meaning yellow spot in Latin and illustrating the connection between lutein and the macula). In addition to physically blocking damaging light rays, these pigments are also potent antioxidants that protect the eye from oxidative stress. These amazing carotenoids are also found in the lens of the eye where they protect proteins in the lens from oxidizing.*

Vegetables and fruits in the red-yellow-orange spectrum are great sources of these important plant pigments. Other foods with the highest amount of lutein and zeaxanthin are egg yolks and corn. The vegetable with the highest amount of lutein is corn, while orange bell and sweet peppers contain the highest amount of zeaxanthin. It might come as a surprise that green leafy vegetables also contain high amounts of lutein, but chlorophyll, which gives these veggies their green color, blocks the orange and yellow pigments from being visible. Meso-zeaxanthin is another form of zeaxanthin that has the same two-dimensional chemical structure, but it differs spatially when looked at three-dimensionally. Although it is not found in the diet, some dietary lutein is converted to this meso- form. Meso-zeaxanthin is also often included, along with lutein and zeaxanthin, in nutritional supplements designed for eye health.

Bilberry

Vaccinium myrtillus (commonly known as bilberry) has an affinity for the tissues of the eye, particularly the retina. Anthocyanin flavonoids have been the subject of interest in bilberry and other blue, red, and purple fruits and vegetables.

These important flavonoids are potent antioxidants. But beyond that, they can benefit the integrity of vascular issue, including blood vessels in the eye.* By strengthening blood vessel walls, circulation is improved, and the blood vessels are less likely to leak; that is, their permeability is decreased.* 

Dietary berry sources of anthocyanins, in addition to bilberries, include blueberries, raspberries, strawberries, black berries, redcurrant, and blackcurrant – with the highest levels found in elderberries and chokecherries. Other sources include grapes, cherries, red cabbage, eggplant, black and purple carrots, pomegranate, plums, purple corn, and purple cauliflower. Are you seeing a trend?

Grape seed extract

Like bilberries, grapes contain anthocyanins, but they are also rich in other polyphenols, including oligomeric proanthocyanins (OPCs). And like bilberry, the polyphenols in grapeseed extract are potent antioxidants and can help preserve the integrity of blood vessels in the eyes and throughout the body.* They support blood flow to the eyes, ensuring proper delivery of nutrients.*

Alpha-lipoic acid

Alpha-lipoic acid (ALA) is an important antioxidant created in the body. It is an antioxidant in both fat- and water-soluble tissues. This allows it to provide benefit to both cell walls (fat-soluble environment) and the interior of a cell (water-soluble environment). Its antioxidant effects protect the sensitive structures of the eye.* For example, ALA can activate antioxidant mechanisms on the surface of the eye (cornea) to help with dry eyes.* The antioxidant benefits of ALA also extend to the retinal ganglion cells that make up the optic nerve and are damaged in cases of glaucoma.*

ALA also has secondary antioxidant effects by helping recycle other antioxidants, including vitamin C, vitamin E, and glutathione – all of which play important roles in maintaining eye health.* For example, low levels of glutathione are implicated in several eye conditions, including cataracts, macular degeneration, and glaucoma.

Omega-3 fatty acids

Omega-3 fatty acids EPA and DHA – such as those found in fatty fish – can benefit the eyes in several ways. DHA is the most significant omega-3 for supporting eye health.* It’s found in high concentrations in photoreceptor cell membranes. In fact, DHA accounts for about 70 percent of all the fatty acids in rod cell membranes – higher than in any other tissue. DHA is essential throughout life, starting in utero, where it plays a key role in brain and vision development.* 

EPA and DHA can also benefit dry eyes.* One study conducted at Brigham and Women’s Hospital found that the participants who had the highest intake of omega-3s in their diets had a 17-percent lower risk of having dry eyes compared to individuals who consumed little to no omega-3s.1

Other nutrients

The above nutrients are by no means an exhaustive list. Other vitamins, minerals, amino acids, and botanical extracts that have known benefits for eye health include vitamins C, D, and E; the B vitamins riboflavin and pyridoxine; the amino acids taurine and N-acetylcysteine (NAC); the minerals magnesium, zinc, and selenium; and the flavonoid plant extracts quercetin and curcumin.

What can Thorne offer?

Following a diet that emphasizes fruits and vegetables rich in flavonoids and carotenoids is a great place to start. Supplementing a good diet with carefully curated nutritional supplements can provide even more benefit.

A clinically studied combination of lutein, zeaxanthin, and meso-zeaxanthin called Lutemax 2020® is included in Thorne’s nootropic formula Memoractiv.* In addition to cognitive benefits, Memoractiv supports eye-hand coordination and can help protect the eyes from too much screen time.*

Another supportive option is Advanced Nutrients, a multi- that includes several eye-supportive nutrients, including vitamins A, C, D, and E, as well as the B complex; the minerals magnesium, zinc, and selenium; and botanical extracts bilberry, lutein, zeaxanthin, and quercetin.*

Reference

  1. Miljanović B, Trivedi KA, Dana MR, et al. Relation between dietary n-3 and n-6 fatty acids and clinically diagnosed dry eye syndrome in women. Am J Clin Nutr 2005;82(4):887-893. doi: 10.1093/ajcn/82.4.887.