Rarely have researchers found that dietary supplements can help prevent or treat diseases, except in the case of classic deficiency diseases such as scurvy (lack of vitamin C) or rickets (vitamin D). That’s why the large clinical trial called the Age-Related Eye Disease Study (AREDS), done by the National Institute of Health's National Eye Institute more than a decade ago, got so much attention. It found that a formula containing high doses of antioxidants (vitamins C and E and beta carotene) and zinc can slow the progression of age-related macular degeneration (AMD) in people who already have this eye disease. Since then, eye care professionals have recommended the “AREDS formula” to people with AMD.
But there have been questions about whether the formula would be more effective and possibly safer if some ingredients were added or subtracted. In May the much anticipated follow-up study, AREDS2, delivered some answers.
AMD is the leading cause of blindness in older people. It starts as a distortion in the visual field, progressing to a “hole” in the macula, the part of the retina responsible for sharp central vision. While there is no cure, some types of AMD can be treated with drugs injected into the eye. About 2 million Americans have advanced AMD and another 8 million have intermediate AMD.
Refining the AREDS formula
Published in the Journal of the American Medical Association, the large new study tested whether the original AREDS formula could be improved by adding omega-3 fatty acids; adding lutein and zeaxanthin (related to beta carotene); removing beta carotene or reducing zinc (25 milligrams instead of 80 per day). Why these changes?
Omega-3s were added because several observational studies (including analyses of the original AREDS subjects) have found that people with the highest dietary intake of these fats in seafood have a reduced risk of developing AMD or progressing to the advanced disease. But these studies did not look at omega-3 supplements.
Similarly, AREDS2 added lutein and zeaxanthin because studies have linked high intakes of these carotenoids (from leafy greens, for instance) or high blood levels of them to a reduced risk of AMD. Lutein and zeaxanthin accumulate in the retina, specifically in the macula, where they act as a filter against ultraviolet radiation and other harmful components of sunlight.
In anticipation of positive results from AREDS2, manufacturers already started adding omega-3s and lutein/zeaxanthin to some of their eye formulas.
There have long been concerns about the beta carotene and zinc in the original AREDS formula. High-dose beta carotene supplements have been found to increase the risk of lung cancer in smokers and possibly former smokers (this is not true of foods rich in beta carotene, such as carrots). High doses of zinc can cause stomach upset and, long term, may depress the immune system and have other adverse effects. Zinc can also lead to copper-deficiency anemia, which is why the AREDS formula contains copper.
Eyeballing the AREDS results
The new study involved 4,000 people who had intermediate AMD and were at high risk for developing the advanced disease. They took one of four formulations daily for five years: the original AREDS formula, AREDS with no beta carotene, AREDS with low zinc or AREDS with no beta carotene and low zinc. They also took one of four supplements or combinations: lutein/zeaxanthin, omega-3s, lutein/ zeaxanthin plus omega-3s or a placebo.
- Adding omega-3s did not increase the benefit of the original formula.
- Removing the beta carotene did not reduce the benefit. That’s good news, since the study found that the risk of lung cancer doubled (2 percent versus 1 percent) in people who took the formula containing beta carotene. This occurred mostly in former smokers, who made up about half the study group. No current smokers were included in the study because of this risk.
- The formula with less zinc was just as effective as the original high-dose formula.
- Overall, lutein/zeaxanthin didn’t help, except when participants had low dietary intakes of these carotenoids.
What to do if you have AMD
If you have AMD, your eye care professional has undoubtedly talked with you about AREDS supplements. Bausch & Lomb holds the patent for the original formula (marketed as PreserVision), but there are copycat products, as well as now AREDS2 formulas. This array of products can be confusing, so ask your doctor for specific guidance. Look for one without beta carotene.
There’s no evidence that the AREDS formula or any supplements help prevent AMD or other eye diseases, even though they are sometimes promoted for general eye health. Still, if you’re at high risk for AMD (because a parent had it, for instance), it’s worth discussing the AREDS formulas with an eye care specialist.
What about cataracts? In the AREDS study, the formula had no effect on the development or progression of cataracts. A secondary analysis from AREDS2 recently found that the lutein and zeaxanthin supplements did not reduce cataract progression.