Seeing your way to the century mark

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Seeing your way to the century mark
June 2007
By John H. Maher, DCCN
Chiropractic Economics

Osteoporosis, diabetes, heart disease, cancer, and senile dementia are major well-publicized chronic diseases that afflict us in our later years.

Less well-publicized is age-related visual impairment from the "big four" Û cataracts, macular degeneration, glaucoma, and diabetic neuropathy. These impairments are the leading causes of impaired vision and blindness in the United States.

Approximately 4 million people have some degree of vision-impairing cataract, and at least 40,000 Americans are blind due to cataracts. Those of you (and your patients) who are ages 52 to 64 have a 50 percent chance of having a cataract. But, you probably won't notice a change in your vision until you reach age 65!

Healthy eye physiology depends upon various nutrients and related compounds. Unfortunately, few North Americans eat the recommended seven to nine servings per day of fruits and vegetables, especially dark greens.1 Indeed, only one out of 20 males in the United States consumes nine servings a day.2

This suggests dietary supplements are essential for ensuring healthy vision. Although most health professionals know vitamin A is important for the eyes, most of us do not fully appreciate the importance of phytonutrients (also known as phytochemicals) to visual longevity.

Three phytonutrients important to eye health are lipophilic (fat loving) terpine carotenoids Û lutein, zeaxanthin, lycopene, and astaxanthin; hydrophilic (water loving) polyphenol flavonoids found in berries; and polyphenol catechins from green tea.

FAT-LOVING CAROTENOIDS

Ô Lutein and zeaxanthin. Lutein and zeaxanthin are the only two carotenoids identified in the human lens. Sometimes referred to as macular yellow, retinal carotenoids, or macular pigment, these carotenoids are natural fat-soluble pigments concentrated in the macula of the human retina. Zeaxanthin is the predominant pigment in the center of the macula (fovea).

These two phytonutrients serve as accessory light-gathering pigments and protectors against the toxic effects of ultraviolet radiation and oxygen. They also appear to protect against phototoxic damage. They play a role in protection against age-related macular degeneration (ARMD) and age-related cataract formation.3

Food sources of lutein and zeaxanthin include green algae, corn, egg yolks, broccoli, green beans, green peas, Brussels sprouts, cabbage, kale, collard greens, spinach, lettuce, kiwi, and honeydew.

Lutein and zeaxanthin are especially abundant in marigolds, giving them their golden brilliance. In green plants, these carotenoids' colors are "hidden" in the green chloroplasts with which they are associated.

According to a referenced report in Nutrition Science News, April 2001, lutein and zeaxanthin may also assist in the prevention of cataracts and glaucoma.4

Ô Astaxanthin and lycopene. Chemically, astaxanthin is similar to beta carotene, though, unlike beta carotene, it is not convertible to vitamin A.

Astaxanthin, a potent antioxidant, comparable to vitamin E,5 is made only by several kinds of algae and plankton. It is eaten by many aquatic species including crustaceans, which are eaten by fish (salmon, trout), which store the pigment in their skin and fatty tissue.

Japanese researchers, who have studied algae, kelp, and other "seaweeds" for decades, have ascertained astaxanthin can improve retinal blood flow;6 modulate parameters of asthenopia Û an eye overuse condition marked by fatigue, red eyes, eye strain, pain in or around the eyes, blurred vision, headache, and occasional double vision;7, 8 improve eye fatigue in healthy subjects, those suffering from visual display terminal fatigue, and those battling sports fatigue;9, 10, 11 and enhance visual acuity in healthy subjects.12

Astaxanthin has exhibited potential mechanisms against oxidative stress, as well as eye stress from everyday activities.

Lycopene is the main carotenoid in tomato fruit. The carotenoid content and composition are highly dependent on the tomato variety and ripeness of the fruit. It is also present in guava, rosehip, watermelon, and pink grapefruit.

Lycopene, a powerful antioxidant, is the most predominant carotenoid in human plasma, present naturally in greater amounts than other dietary carotenoids. This, perhaps, indicates its greater biological significance in humans.13

Studies also suggest lycopene may impact cataract formation.

WATER-LOVING flavonoids

Polyphenols assist in the absorption of potentially damaging ultraviolet (UV) radiation and quench-free radicals from other oxidants. While the impact is considerably less when compared to the phytonutrients lutein and zeaxanthin, anthocyanidins and tea catechins Û water-loving flavonoids Û are among the most promising phenols studied for antioxidant protection in eye health.

Ô Anthocyanosides and related compounds. Abundant in bilberry and other berries, these appear important to overall eye health and visual function. They are usually colored blue or red, or their combination as deep purple.

As early as WWII, French researchers studying Royal Air Force pilots found bilberry extract improved nighttime visual acuity.14 Pharmacological studies have shown a standardized extract of bilberry anthocyanosides increases capillary strength, reduces abnormal vascular permeability, and provides potent antioxidant activity.

These extracts have been shown to promote resynthesis of retinal pigments, benefiting visual acuity.

Anthocyanosides also have proved to lessen ocular fatigue and to assist visual recovery and light and dark adaptation. Benefits have been reported for optic micro-angiopathy, meaning tiny vessel disease, and myopia.15,16,17,18,19

The anthocyanins from a combination extract of bilberry, blueberry, strawberry, cranberry, elderberry, and raspberry have demonstrated a range of positive properties for eye health, including protecting DNA integrity and supporting visual function.20

The polyphenols in French maritime pine bark extract have been studied for the ability to strengthen capillaries and prevent diabetic retinopathy, partially recover visual acuity, improve capillary resistance, and reduce leakages into the retina.21 In 2001, Italian scientists reported two months of treatment with 150 milligrams per day of pine bark extract in patients suffering from diabetic, hypertensive, and atherosclerotic retinopathy led to better retinal integrity and function.22

GREEN TEA

Chinese researchers found tea polyphenols, called catechins, have the ability to prevent oxidative damage in human fetal lenses exposed to metallic oxidation.23

According to Gupta SK et al., administration of green tea polyphenol extract to rats prior to experimental induction of cataract reduced their incidence and severity, suggesting support of the antioxidant systems of the eye.24

Research on epigallocatechin-3-gallate (EGCG), the most studied and powerful antioxidant from green and white tea, suggested an ability to prevent rabbit lens cataract development.25 These findings support the notion that antioxidants from tea polyphenols help delay the onset or progression of age-related cataracts.

In supplementing the above phytonutrients, it has been repeatedly shown that it is best to use a product that provides a wide spectrum of fruit and vegetable concentrates of all colors compared to just one or several individual extracts.