How zinc affects AMD
One of the greatest ongoing food fights in eye care concerns the role of antioxidants and zinc in age-related macular degeneration (AMD) prevention and the movement of genetic testing from the theoretical research lab to applied science.
One of the greatest ongoing food fights in eye care concerns the role of antioxidants and zinc in age-related macular degeneration (AMD) prevention and the movement of genetic testing from the theoretical research lab to applied science.1 Two principals, Dr. Carl Awh and Dr. Emily Chew have done a great service in moving forward this debate. However, amidst battles among dueling statisticians, commercial interests, and NEI recommendations much has been lost in this conversation concerning zinc.
Age-Related Eye Disease Study (AREDS) 1 nutrients are not synonymous with AREDS 2 nutrients because the latter have lutein and zeaxanthin-which dampen the potential for “the high-dose hyper-immune zinc effect” in specific genetic groups by reducing alternate compliment factor D.2 Lampalizumab, one of the most promising Phase 3 drugs for the future intravitreal treatment of geographic atrophic AMD, inhibits factor D.3
Previously from Dr. Richer: Examining poster themes at ARVO 2017
There is “sickness” in evidence-based medicine as described by UK pharmacologists Hickey and Roberts.4 There is no such thing as an average patient, and populations are not people.5 Genetic testing is therefore appropriate and reasonable, especially if one eye is wet, and if only to optimally protect the remaining eye, or in the unfortunate case of monocular AMD-protect the only eye.
The AREDS 1 formula with high-dose zinc has saved lives. As reported in May 2004, AMD patients taking 80 mg zinc per day for high-risk AMD experienced a 27 percent decline in mortality.6
In 2006, Eby and Holcomb wrote about high-dose zinc to resolve angina pectoris. They based the report on other concurring reports from the 1960s and 1970s, and they hypothesized that high-dose zinc (50 to 300 mg per day) decreases high-density lipoprotein (HDL) and increases circulating low-density lipoprotein (LDL) cholesterol.7 The increased LDL blood concentration with mega-dose zinc is believed to be due to the disposal of LDL as it exits the body.
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Eby and Holcomb also emphasized that zinc prevented oxidation (hardening) of LDL cholesterol in the aorta and halted the main mechanism of atherosclerosis. Calcium and iron, in contradistinction, interfere with zinc absorption and zinc activated enzymes-exacerbating atherosclerosis.8
Zinc bioavailability is dependent upon a myriad of environmental factors described below and intestinal metallothionines that are capable of adjusting the absorption of zinc by 15 to 40 percent. Zinc bioavailability is also dependent on the specific supplemental zinc compound prescribed.9
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Zinc for systemic health
Zinc is the second most abundant mineral ion after magnesium and is the only mineral that appears in all enzyme classes.9 Zinc maintains cellular division, cellular growth, and gene regulation.
Zinc is crucial for fertility through maintenance of testosterone and estrogen levels. Zinc helps maintain serum acid base balance through sustaining proper carbonic anhydrase concentrations. Maintenance of normal bones, hair, skin, blood clotting, and thyroid function all involve zinc. Zinc is needed for maintaining a robust immune system through thymus hormone activation and maintenance of balanced prostaglandins for efficient wound healing.9
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Zinc for eye/brain health
Zinc is required for all five senses and cognitive functions. Zinc helps vision by mobilizing vitamin A (as retinol binding protein) from the liver. Zinc helps deliver vitamin A to the eye, where the enzyme alcohol dehydrogenase is responsible for converting retinol to retinal in the visual photo-transduction cycle.
Numerous factors beyond excessive iron and calcium supplementation impair zinc status. Zinc deficiency, especially common in the elderly, is a threat due to:
• Soil deficiency
• Vegan or vegetarian diet preference
• Excessive copper in drinking water from copper plumbing
• Excessive cereal or refined wheat intake
• Excess alcohol and/or high-fructose corn syrup intake
• Climate, sweating, and strenuous exercise
• Medications such as statins, acid blockers, and anti-hypertensive angiotensin-converting-enzyme (ACE) inhibitors
Preventative measures
For males over age 40 and females approaching menopause, zinc supplementation is wise in order to maintain systemic health because the diet provides marginal amounts of zinc. For these patients, suggested dosage is 25 to 30 mg per day with accompanying vitamin B6 (no more than 25 mg) to increase absorption.
I also suggest 200 mcg of selenium to facilitate release of zinc from its binding protein metallothionein.10 While zinc pills don’t cure AMD, taking zinc pills may help AMD patients live longer.
Related: How diet and nutrition affect disease
References
1. Awh CC, Zanke B, Kustra R. Progression from No AMD to Intermediate AMD as Influenced by Antioxidant Treatment and Genetic Risk: An Analysis of Data from the Age-Related Eye Disease Study Cataract Trial. J Vitreoretin Dis. 2017 Jan. 1(1)45-51.
2. Tian Y, Kijlstra A, Webers CA, Berendschot TT. Lutein and Factor D: two intriguing players in the field of age-related macular degeneration. Arch Biochem Biophys. 2015 Apr 15;572:49-53.
3. Sacconi R, Corbelli E, Querques L, Bandello F, Querques G, A Review of Current and Future Management of Geographic Atrophy. Ophthalmol Ther. 2017 Apr. doi: 10.1007/s40123-017-0086-6.
4. Hickey S and Roberts H, Evidence-Based Medicine: Neither Good Evidence nor Good Medicine. Orthomolecular Medicine News Services. 2011 Dec. Available at: http://orthomolecular.org/resources/omns/v07n15.shtml. Accessed 5/31/17.
5. Hickey S, Roberts H. (2011)Tarnished Gold: The Sickness of Evidence Based Medicine. Charleston, SC. CreateSpace Publishing.
6. Clemons TE, Kurinij N, Sperduto RD, AREDS Research Group. Associations of mortality with ocular disorders and an intervention of high-dose antioxidants and zinc in the Age-Related Eye Disease Study: AREDS Report No. 13. Arch Ophthalmol. 2004 May;122(5):716-26.
7. Eby GA, Halcomb WW. High-dose zinc to terminate angina pectoris: a review and hypothesis for action by ICAM inhibition. Med Hypotheses. 2006;66(1):169-72.
8. Jayalakshmi S, Platel K. Supplemental levels of iron and calcium interfere with repletion of zinc status in zinc-deficient animals. Food Funct. 2016 May 18;7(5):2288-93.
9. Claire, A. A Practitioners Guide To Zinc Supplements And How Your Body Uses Zinc. Metabolics. 2013 Dec 16. Available at: http://www.metabolics.com/blog/a-practitioners-guide-to-zinc-supplements. Accessed 5/31/17.
10. Sardi B. Why Your Cardiologist Should Have Prescribed Zinc During Your Last Office Visit. Knowledge of Health. 2017 Apr. Available at: http://knowledgeofhealth.com/why-your-cardiologist-should-have-prescribed-zinc-during-your-last-office-visit. Accessed 5/31/17.
