Age-Related Eye Disease Study
- investigate the natural history and risk factors of age-related macular degeneration (AMD) and cataracts, and
- evaluate the effects of high doses of antioxidants and zinc on the progression of the two conditions in those with AMD.
The study followed 3640 individuals for an average of 6.3 years between 1992 and 2001. The researchers concluded that high levels of antioxidants and zinc can reduce some people's risk of developing advanced AMD by about 25 percent. Those that benefited from the dietary supplements included those with intermediate-stage AMD and those with advanced AMD in one eye only. The supplements had no significant effect on the development or progression of cataracts. "High levels" in this case were defined to be:
- 500 milligrams of vitamin C;
- 400 international units of vitamin E;
- 15 milligrams of beta-carotene (or 25,000 international units of vitamin A);
- 80 milligrams of the dietary mineral zinc, in the form of zinc oxide; and
- two milligrams of copper as cupric oxide, added to prevent copper deficiency anemia, a condition associated with high levels of zinc intake.
The study was followed by AREDS2, a five-year study (starting in 2006) designed to test whether the original AREDS formulation would be improved by adding omega-3 fatty acids; adding lutein and zeaxanthin; removing beta-carotene; or reducing zinc. In AREDS2, participants took one of four AREDS formulations: the original AREDS formulation, AREDS formulation with no beta-carotene, AREDS with low zinc, AREDS with no beta-carotene and low zinc. In addition, they took one of four additional supplement or combinations including lutein and zeaxanthin (10 mg and 2 mg), omega-3 fatty acids (1,000 mg), lutein/zeaxanthin and omega-3 fatty acids, or placebo.
The study reported that there was no overall additional benefit from adding omega-3 fatty acids or lutein and zeaxanthin to the formulation. However, the study did find benefits in two subgroups of participants: those not given beta-carotene, and those who had very little lutein and zeaxanthin in their diets. Removing beta-carotene did not curb the formulation's protective effect against developing advanced AMD, which is important given that high doses of beta-carotene have been linked to higher risk of lung cancers in smokers. According to Dr. Emily Chew, "Because carotenoids can compete with each other for absorption in the body, beta-carotene may have masked the effect of the lutein and zeaxanthin in the overall analysis."
- Age-Related Eye Disease Study Research Group (October 2001). "AREDS Report No. 8: A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E, Beta Carotene, and Zinc for Age-Related Macular Degeneration and Vision Loss". Archives of Ophthalmology. 119 (10): 1417–1436. doi:10.1001/archopht.119.10.1417.
- "NIH study provides clarity on supplements for protection against blinding eye disease". May 2013. Archived from the original on 2013-06-07. "Lutein/Zeaxanthin and Omega-3 Fatty Acids for Age-Related Macular Degeneration. The Age-Related Eye Disease Study 2 (AREDS2) Controlled Randomized Clinical Trial". JAMA. May 5, 2013.
- Age-Related Eye Disease Study 2 (AREDS2)
- Omenn, Gilbert S.; et al. (1996). "Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease". New England Journal of Medicine. 334 (18): 1150–155.