Nutrition & Eye Health

The Role of Nutrition in Age-related Macular Degeneration
Popeye, the spinach-guzzling cartoon character, may have been on to something after all. Although it may not help build huge muscles, there’s now solid evidence that certain nutrients found in spinach and other leafy green vegetables may help prevent or slow down age-related macular degeneration (AMD).

Antioxidants
To understand the connection between AMD and diet, it’s important to first understand what antioxidants are, and why they are important to your health.

Antioxidants are a group of vitamins, minerals and carotenoids that form one of the human body’s first lines of defense against “free radicals”.

Free radicals are a natural by-product of the body’s metabolic process that can damage or even kill healthy cells throughout the body – including those in the eyes. One of the roles of antioxidants is to seek out and neutralize the free radicals. Antioxidants include Vitamins C and E, as well as carotenoids such as beta-carotene.

Healthy, well-nourished people usually have an ample supply of antioxidants to help protect them against free radical damage. But people whose antioxidant levels are low due to unbalanced diets or other factors may be at increased risk for AMD and other diseases.

The Macula
The macula is the small “spot” of central vision-related cells in the center of the retina. If you could see it, it would appear yellow. This is because the macular pigment contains high levels of antioxidant carotenoids, the yellow pigments found in many fruits and vegetables. In particular, two important carotenoids – lutein and zeaxanthin (loo-teen and zee-zan-thin) – make up the bulk of the macular pigment. What’s surprising however, is that our bodies do not make their own supply of lutein (although zeaxanthin appears to be made in the retina from lutein). This means that our supply of these two carotenoids must come entirely from outside – from what we eat. Research is starting to show that the more we eat of foods high in lutein, the higher the density of our macular pigment. Conversely, the less lutein we consume, the lower our macular pigment density.

So, why is the macular pigment density so special? One very good reason is that people with low macular pigment densities have been shown to be more prone to developing AMD. In part, this could be the result of there being fewer antioxidants available to protect the macula from free radical damage. Another good reason has more recently come to light: the macular pigment may help protect against damage from blue light.

Blue Light Damage
Visible blue light, much like ultraviolet light, can’t actually be “seen”, but over time, it can cause damage to the retina, especially the important central vision-related cells in the macula. Exposure to this type of blue light has been identified as another potential risk factor for AMD.

Fortunately, the latest research indicates that the lutein and zeaxanthin in the macular pigment may absorb blue light before it can cause damage. In fact, one recent study showed that a diet rich in lutein and zeaxanthin helped reduce the risk of AMD more than four other types of diets. But unfortunately, evidence also shows that many people are actually consuming less carotenoid-rich foods. The best natural sources of lutein and zeaxanthin are colorful fruits and vegetables such as kale, spinach and kiwi fruit— foods which do not always appear on many Canadians’ tables.

There’s no doubt that the best way to stock up on vital nutrients is to eat a range of healthy foods, however that can sometimes be difficult. If you don’t think you are getting enough lutein, zeaxanthin or other important nutrients in the foods you eat, ask your eye care professional for advice on dietary supplements.

Dietary supplements
Some eye care professionals recommend dietary supplements as a way to ensure their patients have a regular supply of the antioxidants and carotenoids that are so important to overall good health — and to the prevention of AMD as shown in the Age-Related Eye Disease Study.

If you’re concerned that you aren’t getting enough lutein in your diet, you may want to consider taking lutein in supplement form. Supplements containing lutein in addition to the AREDS formulation of vitamins and minerals are available in most pharmacies.

Sensible eating, dietary supplements (if recommended by your eye care professional), and other basic health precautions may help protect your sight from this all-too-common disorder.

References

1. Taylor HR, et al. The Long-term Effects of Visible Blue Light on the Eye. Arch Ophthalmol 1992;110:99-104
2. Cruikshanks KJ, et al. Sunlight and age-related macular degeneration. The Beaver Dam Eye Study. Arch Opthalmol 1993;111:514-518.
3. Bernstein PS, et al. Resonance Raman Measurement of Macular Carotenoids in Normal Subjects and in Age-related Macular Degeneration Patients. Ophthalmology 2002;109(10):1780-1787
4. Pratt SG. What We Now Know About AMD and Nutrition. Review of Ophthalmology 1998;08.
5. Snodderly DM. Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. Am J Clin Nutr 1995;62(suppl):1448S-1461S
6. Landrum JR, et al. A One Year Study of the Macular Pigment: The Effect of 140 Days of a Lutein Supplement. Exp. Eye Res. 1997;65:57

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