Nutrition for Eye Health (Eye of the Beholder)

Seeing the world around us is both helpful to our survival and pleasing to our love of physical imagery. Anything—whether aging, environment or diet—that threatens this vital sense is a threat to quality of life. However, the eyes need not bow to blurry or obstructive visual impairments linked to aging and various ailments, as many compounds found in nature can help shore up eye protection and keep the horizon in full view.

The ability to see is a coordination of the structures of the eye and the nervous system, especially the brain. Light enters the eye through the cornea then passes through the pupil, an opening that controls the amount of light entering the inner eye. It then beams into the bi-convex lens, which focuses the light and sends it through the vitreous humor and onto the retina.

The retina is the innermost layer of the eye and houses the light-sensing components—rods, which “see” in low light, and cones, which sense color and detail. The macula is in the middle of the retina and is home to the fovea centralis, a cone-rich segment responsible for fine detail. Beyond the cones and rods, light is chemically converted to electrical impulses for transmission to the brain via the optical nerve, a channel of retinal fiber at the back of the eye. These signals are processed by the brain, including both the primary and secondary visual cortex.

Any disruption or destruction along this pathway of light and vision can affect eyesight and the ability to interpret the incoming light and signals. Common maladies of the eye include age-related macular degeneration (AMD), cataract, glaucoma and diabetic retinopathy.

AMD is a degenerative consequence of aging and the leading cause of blindness in Western society, especially in those over the age of 60. According to the National Retina Institute (NRI), more than 1.7 million Americans suffer from some form of AMD.

Wet AMD is the less common form but more often results in severe vision loss, as it is more aggressive in its pathology. In wet AMD, abnormal production of new blood vessels in the eye leak fluids and damage the macula. It is almost instantly considered advanced AMD, with only new and experimental invasive procedures offering any relief.

Dry AMD is the more common form, accounting for 80 percent of AMD cases but only 20 percent of cases of severe vision loss, according to NRI. This form of AMD is caused by aging and thinning of retinal pigment epithelial (RPE) cells in the macula, in addition to yellow, crystalline deposits, called drusen. The damage and vision loss associated with dry AMD is generally more gradual, and there are few treatments, including dietary supplementation.

The secret to macular health is in its primary components, lutein and zeaxanthin. These carotenoids comprise the macular pigment, where they filter ultraviolet light and quell oxidative stress. These carotenoids cannot be synthesized in the body, so they must come from the diet. Supplementation with lutein and zeaxanthin increases the macular pigment optical density (MPOD) in the fovea centralis,¹ and serum levels of nutrients, namely lutein and zeaxanthin, are inversely associated with increased MPOD.²

Because low plasma lutein and zeaxanthin concentrations or dietary intake are associated with low MPOD and increased risk of AMD, Johns Hopkins researchers suggested the carotenoid duo be considered conditionally essential nutrients.³

The proof is in the pudding, and the pudding, in this case, is research. The Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study from the Women’s Health Initiative (WHI), showed consuming a diet rich in lutein and zeaxanthin could lower the risk of developing AMD.⁴ However, a subsequent study revealed physical factors may influence the uptake and distribution of the xanthophylls, as MPOD was directly linked to dietary intake of lutein and zeaxanthin, while increased abdominal body fat and diabetes were related to lower MPOD.⁵

Most recently, researchers found four to six months of supplementation with 12 mg/d of a combination of lutein and zeaxanthin (as OPTISHARP® Zeaxanthin and FloraGLO® Lutein, from DSM Nutritional Products), significantly increased MPOD and improved visual performance in glare for most of the 40 healthy subjects (mean age of 23.9) followed for six months and assessed at baseline, one, two, four and six months.⁶

Separately, lutein and zeaxanthin have each impacted AMD and related research.

In the Lutein Antioxidant Supplementation Trial (LAST), visual parameters—including MPOD, visual acuity and contrast sensitivity—were improved in atrophic AMD patients who received either 10 mg of purified lutein (as FloraGLO® Lutein, from Kemin Health) or purified lutein plus a broad spectrum antioxidant (as OcuPower, from Vitacost.com) for 12 months.⁷

Similar findings resulted from administering lutein for six months to patients with foveal fixation.⁸ The University of Pennsylvania researchers reported supplementation significantly increased serum lutein levels in 91 percent of patients and augmented MPOD in almost two-thirds of subjects, although there was no change in central vision.

A pilot study featuring seven early subjects taking 20 mg/d of lutein ester (as XANGOLD®, from Cognis Nutrition & Health)—supplying 10 mg/d free lutein—and six age-matched subjects taking a control supplement for 20 weeks, found supplementation increased plasma lutein and mean MPOD significantly.⁹ The researchers concluded a diseased macula can accumulate lutein and/or zeaxanthin, and the benefits of lutein supplementation could be extended to subjects with established age-related maculopathy (ARM), the early stages of AMD.