Lutein and Zeaxanthin May Help Maintain Normal Visual Function

Carotenoids Can Help Maintain Healthy Eyes
They may also slow the progression of age-related eye diseases
By Dr. Edward R. Rosick

espice, adspice, prospice (look to the past, look to the present, look to the future). These ancient Latin words of wisdom reflect what people throughout the ages have regarded as our most important sense: vision. Although losing one of our other senses, especially our hearing, can be terrible, nothing compares with the disaster of blindness.

For better or worse, we humans are primarily visual creatures - about 80% of all the information we take in is through our eyes - yet eye health is something that most of us take for granted. Just as the health of our heart and other vital organs depends on our lifestyle, including the use (or nonuse) of supplements, the same is true of our eye health, for which certain supplements are known to be beneficial. Among them are the natural carotenoids lutein and zeaxanthin, which are vital constituents of the human eye to begin with.

The Eye Is Like a Camera

The conversion of light waves from the outside world into meaningful visual images in our brains is one of the many wonders of the human body. To help understand how the eye works, think of it as a specialized, complex camera. Just as in a camera, light from the outside must first pass through a lens. In a camera, the lens focuses the light on the film; in the eye, the lens focuses light on the retina, the photochemically sensitive membrane that lines the back of the eyeball. Unlike camera film's captured images, however, the retina's images of the outside world are transmitted further, via the optic nerve to the brain, which stores them (or not) in memory.

With a camera, of course, we can go to the store when we need more film, or buy a new lens if the old one gets broken. Unfortunately, fixing our eyes isn't that easy. Visual loss due to defects in the lens or retina of the eye is a major medical problem in the United States. It's estimated that by age 65, over 30% of people in this country will have some form of vision problem not correctable by eyeglasses or contact lenses. Two of the most common such age-related eye diseases are cataracts and macular degeneration (often called age-related macular degeneration, or AMD).

Cataracts Can Cloud Your View

A cataract is a clouding of the lens of the eye, and this dismal condition affects 13-14 million older Americans. If we again think of the eye as a camera, it's easy to see why having a cloudy lens would make vision more difficult. If a camera lens gets dirty, you can't take decent pictures. In the eye, if the lens becomes clouded, the image that the retina sees becomes blurry.

The lens of the eye is made mainly of water and proteins called crystallins. Normally the crystallin molecules are arranged in a symmetrical pattern that allows light to pass through without distortion, as though the lens were made of glass. If the symmetry is disrupted, however, and the molecules start clumping together randomly, they interfere with the light transmission, and the lens becomes cloudy - a cataract. In the early stages, cataracts do not pose a serious vision problem, but as they grow larger and denser, vision becomes blurry, colors fade, and night vision becomes very poor.

Oxidative Damage May Cause Cataracts

Although scientists aren't yet sure what causes cataracts, research has shown that factors such as smoking and excessive sunlight can contribute to cataract formation. The culprits are thought to be free radicals, deleterious molecules that arise not only from normal chemical reactions in the body but also from exposure to noxious chemicals in cigarette smoke and exposure to solar ultraviolet (UV) radiation.

For those afflicted with cataracts, surgeons can remove the natural lens and replace it with an artificial one made of plastic. Cataract surgery is one of the most common operations in the United States, and at a price of about $1000 per eye, it is one of the most lucrative for doctors (it takes about half an hour). Although it is highly successful and safe, there can be complications (as with any kind of surgery), including eye infections, bleeding, pain, and even total loss of vision.

Macular Degeneration - A Thief of Vision

Age-related macular degeneration is another debilitating eye disease, afflicting over 10 million older Americans. It is the number one cause of legal blindness in people over 60, and, unlike cataracts, it cannot be cured by surgery. AMD affects a small, round, yellow-pigmented spot in the central portion of the retina called the macula lutea, or macula for short. It is the macula that gives us "central vision," the ability to discern fine detail, such as is needed for reading, driving, or working at a craft. The effects of damage to the macula can be devastating, often culminating in blindness.

AMD is of two types, called dry and wet, which account for about 90% and 10%, respectively, of all cases of the disease. In the dry form, tiny lesions called drusen accumulate under the retina and can eventually cause the macula to become thin and stop functioning, resulting in a loss of central vision. There is no treatment for dry AMD, but the good news is that it develops slowly and does not necessarily result in severe vision loss.

Wet AMD Is the Worst

The far more dangerous wet AMD develops more rapidly (it takes about 2 to 3 years for the severe consequences) and accounts for about 90% of all the major vision loss attributed to AMD. It occurs when tiny, abnormal blood vessels grow across and under the macula. Being fragile, they often leak fluid and blood, causing the formation of scar tissue that can damage or destroy the macula.

There are two treatments (not cures) available for wet AMD. One is laser photocoagulation surgery, in which a heat-producing laser beam is used to destroy the abnormal blood vessels. This creates a permanent blind spot in the field of vision, but it is usually less severe than the eventual loss of vision caused by the disease's unchecked development.

The other treatment is an ingenious therapy in which drug molecules are injected into the patient's arm in an inert form and are then photochemically activated in the eye by exposure to a non-heat-producing laser beam. Once activated, they attack and destroy the abnormal blood vessels. This does not cure wet AMD any more than the laser surgery does, but it significantly retards its development.

Lutein and Zeaxanthin - Colorful Antioxidants

To avoid AMD, don't get old, and don't smoke - these are the only two known risk factors for the disease, although there is some evidence that dietary fat intake and obesity may also be factors, as well as your genes (heredity).1 Furthermore, there is evidence that antioxidants, especially in combination with zinc, may be beneficial in reducing the progression of the disease, especially for those who are at high risk of developing advanced-stage AMD. Among the most promising antioxidants are lutein and zeaxanthin. As mentioned earlier, they are carotenoids, which are naturally occurring pigments found in many fruits and vegetables. Many carotenoids are antioxidants.

Lutein and zeaxanthin have a unique ability to concentrate in the eye tissues, especially in the macula. In fact, they are the two primary pigments of the macula, which owes its yellow color to them. The exact roles of these carotenoids in the eye are not fully known, but research continues. In addition to their antioxidant action, it is thought that they may help protect the lens and the retina from photodamage caused by short-wavelength radiation at the blue end of the visible light spectrum, and beyond (the ultraviolet). Although the lens does not stop blue light and UV, lutein and zeaxanthin filter some of this radiation out before it reaches the retina.

Because of the obvious importance of lutein and zeaxanthin in the eye, it isn't a huge leap to think that supplementing with these carotenoids might help protect our vision and perhaps even help stave off cataracts and AMD. Two studies have shown that increasing one's intake of lutein and zeaxanthin will raise the levels of these important carotenoids in the retina.2,3 In both studies, the levels increased in the maculae of people who either took lutein - zeaxanthin supplements or increased their intake of foods rich in lutein and zeaxanthin.

Lutein and Zeaxanthin Fight AMD

A study published in the Journal of the American Medical Association looked at the role of lutein and zeaxanthin and other supplements in the development of AMD.4 This study compared 356 people who had wet AMD with 520 control subjects who had other eye diseases but not AMD. The participants were divided into five equal-sized groups, or quintiles, based on their intake of lutein and zeaxanthin. Those in the lowest quintile (the lowest 20%) had an average daily intake of 0.5 mg of lutein and zeaxanthin, versus 5.7 mg/day for those in the highest quintile.

The results were impressive. The authors concluded that "the risk for AMD was reduced by 43% among people whose consumption placed them in the highest quintile of dietary carotenoid (lutein and zeaxanthin) intake compared with those in the lowest quintile." They also suggested that the carotenoids' effect could be due to their antioxidant action as well as the protection they afford the eye from the damaging effects of blue light.

Lutein and Zeaxanthin Fight Cataracts

Besides protecting against AMD, a high intake of lutein and zeaxanthin may also be protective against cataract formation, as shown by the results of three studies. The first, published in 1998, examined the effects of antioxidant nutrients, including lutein, on the incidence of cataract formation.5 The results showed that people with the highest daily intake of lutein (1.2 mg/day, versus only 0.2 mg/day for those with the lowest intake) had a statistically lower incidence of cataracts.


"The risk for AMD was
reduced by 43% among people
[with the highest levels of]
dietary carotenoid (lutein and
zeaxanthin) intake."


Two more recent studies examined thousands of men (all doctors) and women (all nurses), and the results were encouraging for people who happen to love vegetables that are high in lutein and zeaxanthin (the best sources are dark green leafy vegetables, especially collard greens, spinach, and kale, as well as corn and sweet potatoes). In the study of doctors, the researchers concluded that "men in the highest fifth of lutein and zeaxanthin intake (6.8 mg/day) had a 19% lower risk of cataract relative to men in the lowest fifth (1.3 mg/day)."6 Likewise, the nurse's study showed that "those [women] with the highest intake of lutein and zeaxanthin had a 22% decreased risk of cataract extraction compared with those in the lowest quintile."7

Other Eye-Friendly Supplements

Vinpocetine, a compound extracted from the periwinkle plant, dilates the cerebral blood vessels, improving blood flow to the brain - and to the retina, which probably accounts for its beneficial effects in helping to prevent and alleviate age-related macular degeneration (AMD). Vinpocetine may also help protect against glaucoma, another common age-related eye disease.

Bilberry extract, like lutein and zeaxanthin, has antioxidant properties, and it has been shown to protect against the breakdown of rhodopsin, a red-sensitive pigment found in the retina. Bilberry extract also offers eye protection through its ability to decrease capillary fragility, and it may help protect against cataracts and glaucoma.

Taurine is an amino acid that acts as an antioxidant and may help protect against cataract formation. It is also thought to be important in keeping the retina healthy, which is vital for clear vision.

Vitamins C and E are antioxidants that play key roles in many aspects of human health, including vision. Vitamin C is especially important for eye health (its concentration in the eyes is about 25 times higher than in the blood), particularly in helping to prevent cataracts; it may also lower the risk for AMD.

Riboflavin (vitamin B2) deficiency has been implicated in cataract formation. Several case studies from the University of Georgia have reported the disappearance of cataracts in patients who were given 15 mg of riboflavin daily for nine months.1 Larger studies are needed to confirm these dramatic results.

Zinc is a mineral found in high concentrations in the retina, and it plays a key role in many biochemical reactions that occur there. Some preliminary studies have shown that people with low levels of zinc intake had an increased risk of developing AMD.2

  1. Head, KA. Natural therapies for ocular disorders, part one: diseases of the retina. Alt Med Rev 1999; 4(5): 342-359.
  2. Head, KA. Natural therapies for ocular disorders, part two: cataracts and glaucoma. Alt Med Rev 2001; 6(2): 141-166.

Lutein and Zeaxanthin May Also Protect Against Cancer and Heart Disease

In addition to protecting our eyes against cataracts and AMD, lutein and zeaxanthin may be beneficial against some other diseases of aging, including cancer and heart disease.8 In both of these diseases, the antioxidant action of the carotenoids is thought to be helpful. Some preliminary studies have suggested that both lutein and zeaxanthin may also protect against cancer through their ability to improve the function of the immune system. Other studies have pointed to the possibility that lutein and zeaxanthin may also decrease one's risk for heart disease through their ability to decrease platelet aggregation, the tendency of blood platelets to stick together and form clots that can obstruct the coronary arteries.


"Men in the highest fifth of lutein
and zeaxanthin intake had a 19%
lower risk of cataract . . . [women]
with the highest intake of lutein
and zeaxanthin had a 22%
decreased risk of cataract."


Make Your Eyes a Top Priority

Can one put any price on the value of vision? Of course not. Just try to imagine being blind for the rest of your life, and everything comes into focus, so to speak. Clearly, we all owe it to ourselves to take the best possible care of our eyes. On any health-care priority list, therefore, our eyes must rank high, along with our heart and brain. Although much remains to be learned about the effects of diet and nutritional supplements on eye health, it's important to keep up with what we do know and avail ourselves of every possible advantage that science can offer - all the more so because we all want to live long, and the longer we live, the more proactive we must be to safeguard the precious health that we have.

References

  1. Hyman L, Neborsky R. Risk factors for age-related macular degeneration: an update. Opin Ophthalmol 2002;13:171-5.
  2. Landrum JT et al. A one year study of the macular pigment: the effect of 140 days of a lutein supplement. Exp Eye Res 1997;65:57-62.
  3. Hammond BR et al. Dietary modifications of human macular pigment density. Invest Ophthalmol 1997;38:1795-1801.
  4. Seddon JM et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. JAMA 1994;272(18):1413-20.
  5. Lyle BJ et al. Antioxidant intake and risk of incident age-related nuclear cataracts in the Beaver Dam Eye Study. Am J Epidemiol 1999;149(9):801-9.
  6. Brown L et al. A prospective study of carotenoid intake and risk of cataract extraction in US men. Am J Clin Nutr 1999:70:517-24.
  7. Taber LC et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr 1999;70:509-16.
  8. Mares-Perlman JA et al. The body of evidence to support a protective role for lutein and zeaxanthin in delaying chronic disease. J Nutr 2002;132:518S-24S.


Dr. Rosick is an attending physician and clinical assistant professor of medicine at Pennsylvania State University, where he specializes in preventive and alternative medicine. He also holds a master's degree in healthcare administration.

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