This article is more than 5 years old. Information may no longer be current.
Nutritional supplements — effective when balanced with diet, lifestyle
Click Here to Manage Email Alerts
The role of nutritional supplements in suppressing and combating various ocular diseases is an ambiguous one, as clinical findings have alternately supported and negated their significance.
“Some studies have shown benefit in preventing or slowing the progress of degenerative ocular diseases, while others have shown no benefit,” said Kari Blaho, PhD, of the Emergency Medicine Department at the University of Tennessee at Memphis. “To complicate the picture, some vitamins have been shown to be of benefit in some diseases, but increase the risk of other diseases.”
Despite these conflicting data, practitioners can maximize the effectiveness of nutritional supplements by using them in a practical and case-specific manner.
Vitamins and AMD
One ocular disease in which nutrition plays an especially prominent role is age-related macular degeneration (AMD).
“For AMD, there are three categories of substances that seem to be efficacious in decreasing the risk of disease,” said Jerry Rapp, PhD, a professor in the Department of Biological Sciences at the State University of New York College of Optometry. “These three categories include zinc, antioxidants and carotenoids.”
The Age-Related Eye Diseases Study (AREDS), conducted by the National Eye Institute, recently found that a combination of antioxidants and zinc reduced the risk of AMD progressing to an advanced condition. Daily doses, including vitamin E supplements of 400 IU, were used in a 6-year test of patients.
In this study, researchers divided patients into four groups and followed them on average for more than 6 years. At the end of the study, the group that took a combination of antioxidants, including vitamin E, with zinc had the lowest risk of progressing to a more advanced stage of macular degeneration.
According to Dr. Rapp, antioxidants are effective because they protect against oxidizing agents generated during metabolism and by light. The most important antioxidants are vitamins C and E, as well as beta-carotene, Dr. Rapp said.
Zinc’s mechanism of action in fighting AMD is not fully understood, Dr. Rapp said. “One idea is that AMD is a disease of the retinal pigment epithelium (RPE), and zinc is a cofactor of certain enzymes that function in the RPE,” he said.
Dr. Rapp said his most recent recommendations in terms of supplementation for AMD are based on the AREDS report #8, which was released in 2001. He recommends 500 mg of vitamin C, 400 IU of vitamin E, 15 mg of beta-carotene and 80 mg of zinc (as zinc oxide) and 2 mg of copper (as cupric oxide).
Cataracts and supplements
For age-related cataracts, the results of the various studies are more equivocal, Dr. Rapp said. “The lens has an oxidative defense mechanism as part of its biochemical constitution,” he said. “Part of that mechanism consists of the antioxidants vitamin C, vitamin E and carotenoids. Some studies suggest that these substances decrease the risk of cataract.”
However, the most recent study, AREDS report #9, found that vitamins C, E and beta-carotene had “no apparent effect on the 7-year risk of the development or progression of age-related lens opacities or visual acuity loss,” Dr. Rapp said.
Nevertheless, Dr. Rapp said he would recommend these supplements for those who might be at risk for developing senile cataract. He said he would recommend the same amounts he advised for AMD. “For those at risk, or for those who might just be concerned about it, a supplement of these three substances at the dosage levels indicated above would probably be a good idea,” he said.
Other possible uses for antioxidants
Antioxidants have also reportedly had effects on other ocular anomalies, according to some practitioners.
“In my experience, ocular allergies will respond to high doses of antioxidants,” said Jeffrey Harris, MD, director of the Whole Eye in Rochester, N.Y. “If I have patients who have allergy problems, I will talk to them about their general health and what other medications they are taking. I have had some fascinating experiences in this area.”
Dr. Harris added that neurological findings have suggested that antioxidants might have neuroprotective capabilities, which could be useful for glaucoma patients.
“There is not much support of this yet in the ophthalmic literature,” Dr. Harris said. “But findings in neurology have shown that if you take animals and create a situation where they have a stroke, the brain seems to resist the lack of oxygen more if the animal was on high doses of antioxidants beforehand.”
The effect of carotenoids
The biological function of these plant-derived compounds, specifically lutein and zeaxanthin, is not fully understood. One proposed function is based on the fact that lutein and zeaxanthin specifically absorb blue light, the highest energy and therefore most damaging visible wavelengths of light that actually reach the retina.
When lutein and zeaxanthin are deficient, the retinal cells may be more susceptible to photodamage from blue light, Dr. Rapp said.
The amount of lutein and zeaxanthin in the macula appears to be important to eye health. The capacity to increase macular pigment density has been demonstrated using pure lutein dietary supplements at higher dosages, as well as bilberry extract as a low-dose lutein supplement.
Dr. Rapp said his recommendations for lutein would be 30 mg daily. For Dr. Harris, the dosage would depend upon the patient.
“It depends upon the situation,” he said. “If it is for prophylaxis in a patient without risk factors, I will recommend about 5 mg a day, and if the person has an actual problem or is at higher risk, I will recommend 10 mg a day or more, as well as other supplements.”
Diet, lifestyle: a solid foundation
A fundamental aspect of nutrition and ocular health is the natural absorption of these vitamins through diet.
“I talk about diet with every patient, whenever I talk about supplements,” Dr. Harris said. “The problem is, the American diet stinks. Even when you think you have a good diet, unless you are growing your own food and know what’s in the soil, you really don’t know exactly what nutrients are in the soil or how long the food has been sitting out.”
Dr. Harris added, however, that he advises patients on how to improve their eye health through diet “if a patient has no signs of a problem or if the problem is in his or her family but the patient has shown no signs of it,” Dr. Harris said. “If a patient has spinach and collard greens in his or her diet, he or she can continue to eat that a few times a week and that will probably be sufficient.”
Dr. Blaho stressed the importance of the patient’s whole lifestyle in determining ocular health. “Some recent data (within the past 5 years) have shown that dietary choices are important,” she said. “For example, flavonoids, isoflavonoids, carotenoids and thousands of other phytochemicals have been shown to contribute a beneficial effect.”
Dr. Rapp outlined some “cardinal rules” regarding basic lifestyle choices that are conducive to ocular health. “Do not smoke, and strive for an ideal weight,” he said. “Do not consume more calories than you need, and limit intake of fats, especially saturated fats. Limit your intake of red meat, and exercise.”
Dr. Blaho cautioned that while vitamin supplements can be beneficial to patients, practitioners should not be overly liberal in recommending them.
“One must consider the cost of these supplements, their drug interactions and compliance,” she said. “We must remember that these agents are drugs and have pharmacological effects. Many patients consider vitamins and other supplements to be ‘safe’ just because they are ‘natural’ and assume that more is better. That is certainly not the case.”
For Your Information:
- Kari Blaho, PhD, is a practitioner at UT Medical Group, Dept. of Emergency Medicine and Clinical Toxicology. She can be reached at 842 Jefferson Ave., Memphis, TN 38103-2817; (901) 545-8699; fax: (901) 545-8996; e-mail: Kblaho@aol.com.
- Jerry Rapp, PhD, is a professor in the Department of Biological Sciences, SUNY College of Optometry. He can be reached at 33 West 42nd St., New York, NY 10036; (212) 780-5170; fax: (212) 580-5174; e-mail: jrapp@sunyopt.edu.
- Jeffrey Harris, MD, practices at the Whole Eye in Fairport, N.Y. He can be reached at 310 Perinton Hills Office Park, Fairport, NY 14450; (585) 223-5990; fax: (585) 223-6047.