Study under review: Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration
Age-related macular degeneration (AMD) is a common vision problem estimated to affect 6.5% of the U.S. population over 40 years old. Adults over 60 have a higher rate of AMD (13.3%) compared to people ages 40-59 (2.8%). In people of European descent, age explains 20% of the variation in AMD prevalence and there is a strong association between age and the likelihood of progressing to more severe forms of AMD. Overall, AMD is the most common cause of vision loss and blindness among the elderly in industrialized countries.
The basics of AMD are summarized in Figure 1. It progresses through several stages, defined in part by the size and number of drusen (yellow lipid deposits) under the retina. Early AMD is diagnosed by the presence of medium-sized drusen, which are about the width of an average human hair. Transition to late AMD is characterized by growth of the drusen and damage to the macula (the part of the retina responsible for high-resolution vision), possibly leading to vision loss. There are two types of late AMD: geographic atrophy in which there is a gradual breakdown of the light-sensitive cells and supporting tissue in the macula that convey visual information to the brain, and neovascular AMD in which abnormal blood vessels grow underneath the retina that cause swelling and damage. It is possible to have AMD in one eye only, or to have one eye with a later stage of AMD than the other.
The eye is subject to high levels of oxidative stress due to the combined exposures of light and oxygen, which suggests that antioxidant supplementation might help prevent or treat eye diseases such as AMD. Numerous observational studies have associated diets rich in antioxidants with a reduced risk of developing AMD, but just because people who eat antioxidant-rich foods have a lower risk of AMD does not mean that the antioxidants per se are protective. Moreover, intervention studies with antioxidant supplements have reported disparate outcomes. The Cochrane Collaboration had previously assessed the ability of antioxidant vitamin and mineral supplements to prevent and delay the progression of AMD in 2012. The two meta-analyses under review are updated versions of these previous publications, incorporating studies published between 2012 and 2017.
AMD, a leading cause of vision loss among the elderly, is characterized by the appearance of drusen on the macula and retinal damage. It has been proposed that antioxidant supplementation might help prevent the development or delay the progression of AMD. The two meta-analyses under review are updated versions of previous Cochrane Database publications investigating whether antioxidant supplementation can prevent or delay AMD.
Other Articles in Issue #36 (October 2017)
Interview: Kelsey Kinney, MS, RD
Registered dietitian, blogger, and podcaster Kelsey Kinney shares her wealth of knowledge about how gut bacteria can impact digestive health, and discusses how the concept of functional medicine plays a role in her work.
Interview: Brad Schoenfeld, PhD, CSCS
Have questions about load’s effect on hypertrophy, supplements with the strongest evidence base, and effective weight loss strategies? Researcher and renowned body composition expert Brad Schoenfeld has answers.
Lifting the weight of anxiety
Aerobic exercise has been shown to be moderately effective for reducing anxiety. Does resistance training have similar benefits?
Blood sugar and spice
Cinnamon’s been used for medicinal purposes for millennia. Research from the past few decades suggests it may also be useful for controlling blood sugar. But is it?
Can dieting actually suppress food craving?
It makes sense that the body would signal the brain to crave certain nutrients during dieting, since overall nutrient intake is cut. The truth may be a little more complicated.
Be the tortoise or the hare: it doesn’t matter for fat loss
Interval training and moderate-intensity aerobic exercise can affect the body in different ways. But do these differences extend to fat loss?
Something smells fishy: is your fish oil oxidized?
Previous research found that a lot of fish oil being sold in New Zealand was subpar. Newer research out of Australia says otherwise.