health guides

Carotenoid supplements improve vision

The study included 60 older people with mild to moderate AMD. All but three of the participants were male and their average age was 75. They were divided into three groups: one group received 8 mg of zeaxanthin per day, another group received 8 mg of zeaxanthin plus 9 mg of lutein per day, and a third group received 9 mg of lutein per day. Visual tests were performed at the beginning of the trial and after four, eight, and twelve months of treatment.

The study’s authors reported the following findings:

• The total amount of pigment in the macula increased from low-normal to normal in all three groups. Higher amounts of macular pigment are believed to protect the retina from the damaging effect of sunlight.
• Visual acuity (sharpness) in high contrast conditions, such as bright light, improved most in the zeaxanthin group, while the lutein group saw the most improvement in their ability to distinguish shapes in low contrast conditions.
• The men receiving either zeaxanthin alone or lutein alone improved more on vision tests than the men receiving both. The study’s authors proposed that the unnaturally low ratio of lutein to zeaxanthin used in the study (almost 1:1, compared to roughly 5:1 in plants) may have been the source of this finding. The influence of the ratio of lutein to zeaxanthin on their absorption and metabolism is still unknown.

Pigments in vision-producing cells

The study’s authors pointed out that zeaxanthin primarily enhanced the aspects of vision that are related to the function of the cone cells of the retina, cells that naturally concentrate this pigment. Lutein is naturally concentrated in the rod cells of the retina, and the men who supplemented with lutein saw the most benefit in the aspects of vision for which the rods are responsible. They concluded that, while there was considerable overlap between the effects of lutein and zeaxanthin in men with AMD, their differences make them complementary.

“We believe that patients with AMD, particularly those short of catastrophic end stage disease, might want to enhance their declining vision with carotenoids,” they said.

Don’t forget your greens

You can take steps to reduce your likelihood of developing vision-dimming macular degeneration as you age:

• Eat foods that contain zeaxanthin and lutein. Studies have found that people who eat spinach, kale, collard greens, and other lutein and zeaxanthin-rich foods have a much lower risk of AMD than people who avoid those foods.
• Wear protective sunglasses. Sunlight exposure increases the damage to rods and cones, which can lead to AMD.
• Include fish regularly. Preliminary research suggests that eating fish more than once per week can reduce the risk of developing AMD.
• Consider an antioxidant supplement. Antioxidents like zinc, selenium, and vitamins C and E appear to protect aging eyes.

(Optometry 2011;82:667–80)