Nutritional influences might help prevent individuals from progressing to advanced AMD.
Although many studies show that nutritional intervention can slow the progression of age-related macular degeneration, there is still no way to forestall its development or reverse its course. There aren’t studies showing that nutrition (or anything else) might forestall AMD. However, if we look carefully at the molecular changes that happen, we can extrapolate how supporting the eye with nutrients might help prevent AMD from starting.
A BETTER ZINC?
The largest studies of nutritional treatment for AMD are the Age-Related Eye Disease Study (AREDS) and Age-Related Eye Disease Study 2 (AREDS 2). The original AREDS formula, consisting of beta carotene (15mg), vitamin C (500mg). vitamin E (400 IU), zinc oxide (80 mg) and copper oxide (2 mg), slowed the progression of AMD from stage III to stage IV (the most advanced stages).
Quality supplement formulations include a more bioavailable form of zinc than the formulation used in AREDS and AREDS 2, which was poorly absorbed zinc oxide. Zinc monomethionine is balanced with the scientific standard ratios of both copper and manganese to stimulate manganese superoxide dismutase, which is required to neutralize both singlet oxygen and super-oxide free radicals.
The 80mg of zinc used in the AREDs formulation was based on a single nutrient study published more than 35 years ago. The Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine recommends an upper limit of 40mg per day for daily zinc supplementation. Some formulas use 50mg as the maximum amount of zinc safe for daily consumption.
Zinc has also been studied in relation to its influence on the progression of AMD, especially in individuals genetically predisoposed to advanced AMD. A pharmacogenetic analysis of the original AREDS data set showed that components of the AREDS formulation may be beneficial or harmful depending on a patient’s genotype in the complement factor H age-related maculoptathy susceptibility 2 genes.
The Vita Risk pharmacogenetic analysis from Arctic Dx, helps determine whether AREDS/AREDS2 vitamin supplements will help or harm the vision of individuals with dry AMD or individuals who have lost sight to advanced AMD (i.e., wet AMD or geographic atrophy in one eye).Depending on an individual’s genetics, some patients derive no benefit and may even be harmed by this treatment, while others benefit greatly. This test may be done alone or with the Macula Risk test, which determines an individual’s genetic predisposition to developing advanced AMD.
AREDS 2 showed a moderate effect from adding two carotenoids—lutein and zeaxanthin, which make up the macular pigment—to the AREDS formula while removing beta-carotene. The AREDS 2 formula also proved effective in slowing the progression to advanced AMD.
Lutein helps protect the macula against damage from blue light and other parts of the body, such as the lens and the brain, from damage by free radicals. Established science strongly suggests a central macula preference for zeaxanthin over lutein. A quality supplement should contain at least 4mg of zeaxanthin. RPE65 is the key enzyme needed to convert lutein to the centrally located meso-zeaxanthin. Thus, adequate intake of lutein is critical for macular protection.
Many commercial formulations use beta-carotene as the source of vitamin A. However, excessive amounts of beta-carotene interfere with absorption of lutein and zeaxanthin. Research also has linked beta-carotene to increased rates of lung cancer in smokers who also consume alcohol.
Keep in mind that body mass index plays a factor in eye health. Specifically, the amount of body fat an individual has affects the amount of lutein and zeaxanthin in the retina. These nutrients are stored in fat tissue and are not available to the eye, even when needed. So, you should probably discuss weight factors with your patients who have AMD.
Anthocyanins are a class of pigments that occur naturally in plants. These antioxidants increase intracellular vitamin C levels, improve ocular microcirculation and protect the vascular endothelium. They also inhibit collagen destruction and decrease the fragility of capillaries.
Another group of antioxidants, the bioflavonoids further prevent the oxidation of low-density lipoprotein, which plays a key role in vascular damage. Bioflavonoids work synergistically with vitamin E to protect the rod outer segments and the retinal pigment epithelium from free-radical-induced membrane lipoperoxidation and damage.
A third antioxidant, coenzyme Q10, regenerates circulating antioxidants and provides nutritional support for the vascular system. It is also essential for producing adenosine triphosphate (ATP) energy from the mitochondria in our cells. Patients who take statin medications such as Lipitor (atorvastatin) and Zocor (simvastatin) are likely to have a deficiency of this enzyme.
Given that drusen appear in the RPE, we should see why disruption of this membrane occurs. Peer-reviewed studies strongly suggest that acetyl-l-carnitine and lipoic acid, also known as alpha lipoic acid, greatly enhance nutrient cellular delivery while providing increased ATP energy to the cells of the RPE. This data was confirmed in an Italian study that found a combination of acetyl-l-carnitine, coenzyme Q10 and fish oils actually reversed some of the physical manifestations of AMD.
Many eyecare practitioners recommend that their older patients take antioxidant supplements to prevent or halt the progress of macular degeneration. Many studies support the inclusion of a well-rounded combination of antioxidants to slow macular degenerative changes. For AMD patients, it is prudent to offer a multiple vitamin and mineral supplement that contains potent amounts of full-spectrum supplemental nutrients and antioxidants.
Remember that the eyes are not only an integral part of the body but directly connected to the brain, which is the most biologically active tissue in the body. So, we cannot underestimate the role of nutrients in maintaining the patient’s ocular and overall health. OO
Jeffrey Anshel, OD, FAAO, is founding president of the Ocular Nutrition Society and is in private practice in Encinitas, CA. Anshel also serves on the advisory board for Optometric Office.