Growers and Grocers

There is now more reason for us to heed our mother’s advice to eat our vegetables. An epidemiological study at the University of Wisconsin found that American women below 75 years old with a regular diet rich in phytonutrient carotenoids lutein and zeaxanthin may have a lower risk of developing eye diseases such as cataracts and age-related macular degeneration (AMD). AMD is the leading cause of vision loss and blindness in Americans aged 65 and older.

What is Age-related Macular Degeneration?

Age-related macular degeneration (AMD) is a disease associated with aging that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving.

AMD affects the macula, the part of the eye that allows you to see fine detail. AMD causes no pain.

Although age is the greatest factor in developing AMD, other elements also contribute to increasing the risk of developing the disease. Other causes may include:

• Smoking - The British Journal of Ophthalmology linked increased risk of vision loss in about 25% of AMD cases to smoking. Constant exposure to second-hand smoke doubled the risk. Cigarette smoke is believed to destroy carotenoids.

• Obesity/Inactivity - Overweight patients with early AMD are at high risk of progressing to Advanced AMD compared to those patients within normal weight limits. Inactivity also suggests increased risk of promoting advanced AMD compared to patients with increased activity up to 3 times weekly.

• Race - White Americans are much more likely to lose vision compared to African Americans.

• Heredity - Recent studies show that people with a family history of AMD have an increased chance of developing the same disease.

• Gender - Women appear to be at greater risk than men.

• Hypertension - Investigative Ophthalmology and Vision Science connected high blood pressure to the development of AMD.

• Eye Color - Similar to the increased incidence of skin cancer in fair-skinned people, some researchers believe that lighter eye color factors increased risk of developing AMD due to lesser pigmentation. However, other studies contradicted these findings.

• Drug Side Effects - Studies link AMD as possible side effects of some anti-malarial and anti-psychotic drugs.

Normal Vision*

Blind spot caused by AMD*

*Photo courtesy of The National Eye Institute


Carotenoids and AMD

The most common form of carotenoids found in North American diets are alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, zeaxanthin, and lycopene. These are the yellow, orange and red pigments that are synthesized in plants.

The carotenoids mostly found in the eye are lutein and zeaxanthin. Of which, the highest concentration are found in the macula. Lutein and zeaxanthin are believed to protect the eyes from light-induced oxidative damage caused by the blue light absorption capacities of the macula. It is theorized that these carotenoids either block or neutralize the oxidants formed in the retina.

Phytonutrients lutein and zeaxanthin are found in common fruits and vegetables: lutein in egg yolks and bright yellow vegetables and zeaxanthin in eggs and dark green leafy vegetables. Chlorophyll, the green pigments in leaves that converts sunlight into energy masks the zeaxanthin pigmentation in some vegetables.

Foods that contain these phytochemicals include:

• Eggs
• Kale
• Spinach
• Turnip
• Greens
• Collard greens
• Romaine lettuce
• Broccoli
• Zucchini
• Corn
• Garden peas
• Brussels sprouts
• Leeks
• Yellow and orange peppers
• Summer squash
• Pumpkin

Lutein and zeaxanthin are fat-soluble phytonutrients and are best absorbed with dietary fat in a meal. Chopping, pureeing, and cooking carotenoid-containing vegetables in oil generally increases the bioavailability of the carotenoids they contain. Although research shows that the longer tomatoes are cooked, the more the carotenoid lycopene is released, prolonged cooking of green leafy vegetables is believed to have the opposite effect, reducing lutein content.

Despite encouraging results from the study, scientists, however, are reluctant to recommend lutein and zeaxanthin supplements at this point, as more studies are needed to verify if the same benefits can be reaped compared to natural sources.

Unlike cataract that can now be treated by out-patient surgery, complete recovery from vision loss due to age-related macular degeneration is unlikely. Early detection and prevention is still our best defense. The
Amsler-grid test is often used by eye doctors to detect early signs of AMD. Here is a link to try the Amsler grid test yourself.