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Vitamins Vitamin Supplementation: What Do You Tell Your Patients?Definitive answers remain elusive on the benefits of supplementation. Patients will still look to you for advice.Michael
Beime, That phrase ends nearly every report regarding nutritional supplements for vision-related diseases and overall eye health. Studies on the effects of vitamin supplementation on specific eye diseases are relatively new, mostly ongoing and oft times confusing—depending on who is spinning the results. “It’s very difficult to design a laboratory experiment to learn about nutrition in the eye,” says David A. Newsome, MD, nutrition author and medical director of the Retinal Institute of Louisiana and Family Eye Centers in New Orleans. Among other issues, the multi-factorial nature of most diseases “makes it more likely to get conflicting information from various investigators,” he adds. The dearth of consistent scientific support has done little, however, to slow the nearly $15 billion-a-year supplementation juggernaut. In the meantime, what should you tell your patients? Here’s some advice from researchers and others close to the issue. Evidence from Studies The antioxidant vitamins A, C and E, the herbal extract ginkgo biloba, and carotenoids lutein and zeaxanthin have shown some positive impact counteracting processes that result in disease. Last year, the Nurses Health Study reported a lower prevalence of early lens opacities among women taking vitamin supplements for more than 10 years. Allen Taylor, PhD, director of the lab for nutrition and vision research at Boston’s Tufts University, and his colleagues observed 600 women in that trial, obtaining 15 years of dietary information and performing eye exams using the Lens Opacities Classification Sys-tem. Women who took 300-400 mg of vitamin C daily had a 77-percent decreased incidence of age-related cataracts over 10 years.1 One of the largest studies, the Age-Related Eye Disease Study (AREDS), under the auspices of the National Eye Institute, is nearing completion. The 10-year study assigned 4,757 participants with none to varying degrees of eye diseases to treatment with four supplement groups: zinc, beta carotene and vitamins C and E, a combination of those nutrients, or a placebo. Researchers are following the group for a minimum of five years, and a principal goal is to determine whether any of the groups develop fewer cataracts or cases of age-related macular degeneration (AMD). The medical community is very anxious for the results. The AREDS may release information as early as next Sep-tember, according to Robert Abel, MD, author and clinical professor of ophthalmology at Thomas Jefferson University in Philadelphia. “Because there is a feeling that something is brewing, they are going to open AREDS in eight years instead of 10,” says Dr. Abel. “It is going to be a landmark decision in people’s confidence level. As a major, double-masked study, it will become the hallmark for whether there is value for nutrition in age-related diseases, especially macular degeneration.” Researchers point to the studies done with lutein and zeaxanthin, carotenoids found to be concentrated in the macular area of the retina. Lutein may act as a filter to protect the macula from potentially damaging forms of light. Two studies by Johanna M. Seddon, MD, and researchers at Harvard University suggest evidence that lutein may help prevent cataracts. A 12-year prospective study of more than 70,000 female nurses ranging in ages from 45-71 charted that nurses with the highest intake of lutein and zeaxanthin had a 22-percent lower risk of cataract extraction compared with those who took little of the carotenoids.2 Another study found that men with the highest consumption of lutein/zeaxanthin had a lower risk of cataract extraction than those with the lowest intake.3 Should You Recommend? Opinions vary widely on recommending or prescribing supplements for eye disease and for general eye health. Spencer T. Thornton, MD, an ophthalmologist in private practice in Nashville, recommends supplements to his patients and feels other physicians should take his lead. He says he first discusses the patient’s lifestyle, diet and habits in relation to the health of his eyes, and then prescribes what he feels is indicated for that patient (See “What One Practice Does,” p. 53). “A number of citations have shown that the usual American diet is deficient in a number of vitamins and minerals necessary for maintenance of good health,” says Dr. Thornton, a paid consultant and chairman of the visual wellness advisory board for supplement manufacturer ScienceBased Health (Corte Madera, Calif.). Recommending supplementation is definitely not a consensus, though. “At this point, I don’t think that ophthalmologists should recommend supplements for their patients,” says Donald Fong, MD, MPH, director of vitreoretinal surgery at Kaiser Permanente Medical Center in Baldwin Park, Calif., and an assistant clinical professor at UCLA School of Medicine. “The evidence does not support it. If you do it, you’re doing it without any backing. And how much would you supplement? There’s no evidence to support a dose, let alone an effect.” Whether you recommend or reject supplementation, staying on the sidelines is no longer an option. As patients become more interested in and knowledgeable of vitamin supplementation, they expect their doctors to do the same. “The ophthalmologist telling his patient that ‘I wouldn’t do it, or it doesn’t work,’ is not going to be enough” to deter most patients, says Dr. Abel. “[Physicians] need to pay attention to the literature out there.” Risks Involved The benefits and the appropriate level are just two parts of the debate over dietary supplementation. Might it do more harm than good? “It used to be thought that vitamin supplements can’t hurt and might be helpful, sort of like chicken soup. But now we know they may hurt,” says Dr. Fong. Guidelines, though fuzzy, do exist. John Hathcock, PhD, a vitamin-toxicity expert with the U.S. Food and Drug Administration’s experimental nutrition section, says there are no official limits for maximum doses, only recommended daily allowances (RDA) at the low end. Dr. Hathcock states that, if you take supplements, your goal is to stay within the “vitamin zone,” that range beginning in the federal government’s RDA and ending “at a level that is still safe and well below the toxicity level.” Also, be cognizant of Dietary Reference Intake (DRI) guidelines, first released in 1997 by the National Academy of Sciences (NAS). The NAS reviews research on supplements, establishing a set of four values that make up the DRIs. It sets the UL at a level that does not pose any risk of side effects for most healthy people. Dr. Newsome says that following these recommended dosages presents little risk. “Take a recommended dosage, but don’t think that more of everything is better,” he says. “Some of these particular ingredients do have toxic limits that are very real.” Fortunately, say some, it may be difficult to overdose. “The people who megadose tend to be retinitis pigmentosa people who hear vitamin A may help, so they will do tons of it,” claims Dr. Abel. “You need large amounts over years [for the dosage] to become toxic.” Even if toxicity weren’t an issue, interference may be. Dr. Fong points out that we know little about how supplements may affect other substances. “There are 50 different carotenoids out there. If you take one, you may block the absorption of the other 49,” says Dr. Fong. “You might think that the macula needs lutein, and the observational evidence suggests that; but it might need other things. If you block the absorption of the other ones, you might be harming it.” And there’s the rest of the body to consider. “For example,” says Dr. Fong, “in the beta carotene studies with lung cancer, the observational evidence suggests that you need higher carotenoids in the diet to lower the risk of lung cancer.4 But when you supplement, the risks went up. It’s thought that you’re blocking the absorption of the needed carotenoid.” Prescription medications, too, may be affected. “Patients on coumadin or other blood thinners can be harmed by excess vitamin E, which also thins blood,” says Dr. Thornton. “When vitamin E is given in high doses with beta carotene in insulin-dependent diabetics with retinopathy, the disease appears to increase in severity.5 Vitamin K can reduce the effectiveness of prescribed blood thinners. Too much zinc can block the absorption of copper, an essential trace mineral in the formation of blood in bone marrow, and anemia can result. Excessive levels of zinc may actually elevate serum lipids and increase the risk of cardiovascular disease.” Dr. Thornton says the main reason for discouraging self-medication is that patients can easily be misled by advertisements and lay recommendation. “The public is hungry for accurate information,” he says. “If it is not forthcoming from the physician, the public will listen to whoever speaks with authority. It is essential for the caring physician to monitor the medications of his patients, including nutritionals.” Diet Is the Key First and foremost, physicians and researchers agree, is implementing a proper diet. “The diet is the place to intervene,” stresses Dr. Fong. “Eating a healthy diet is the way to go, eating a variety of foods so the body can absorb what it needs, and making sure it’s low in fat and high in fruits and vegetables.” Research is backing up the contention that eating fruits and vegetables is associated with a lower incidence of AMD. Also, in a study from the Johns Hopkins Medical Institution in Balti-more, researchers found a higher antioxidant capacity in 83 people who consumed eight to 10 servings of fruits and vegetables a day than in 40 others who ate fewer servings.6 Dr. Abel points to daily doses of the food pyramid items: at least five to eight fresh fruits, specifically oranges, tomatoes and apples, and half-cup servings of vegetables, notably spinach and carrots. Dr. Newsome says his patients can obtain the nutrients they need by eating plenty of green, leafy vegetables. If the patient insists on augmenting a healthy diet with vitamins, he recommends a broad-spectrum vitamin antioxidant supplement that has lutein in it. “We give patients some of the basics to look for and tell them to get the supplement that has at least 2 mg of lutein in it and at least one RDA of zinc, that has other minerals and other antioxidants like vitamins E and C, some of the vitamin A family, the carotenoids and selenium,” he says. “We also tell them to get the one that is the cheapest.” Keeping Informed Failing to maintain a working knowledge of current developments can label you as outdated. “Patients are becoming better in-formed through the lay press and are prepared to ask questions,” says Dr. Thornton. “If the doctor simply passes it off by saying something disparaging or that he ‘doesn’t believe multivitamins make any difference,’ the patient will get the idea that he does not keep up with current knowledge, or just isn’t interested in his patients’ needs.” The subject of supplementation is new territory for most ophthalmologists, and it wasn’t stressed in medical school. “There needs to be more on nutrition and eye disease in medical training,” adds Dr. Fong. “When I was in school, there was little discussion on it, especially micronutrients.” So how do you keep up with the information out there? Recommendations include attending seminars and keeping up with journals, books and health-news websites, and conferring with conventionally trained nutritionists and dietitians. Dr. Newsome says to look at the weight of the information as a whole. “Look at the scientific strengths and weaknesses of the studies that are put forth and really look at it in the balance,” he adds.
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