(RxWiki News) The body can use different types of antioxidants and omega-3 fatty acids to promote good health. But supplements may not be able to keep vision clear from cataract cloudiness later in life.
A long-term clinical trial tested the use of certain nutritional supplements to see if they helped reduce the risk of developing serious cataracts.
The results of the study showed that nutritional supplements did not affect the chances of developing cataracts in a healthy population.
"Eat plenty of fruits and vegetables."
Emily Y. Chew, MD, chair of the Age-Related Eye Disease Study 2 (AREDS2) Research Group at the National Eye Institute, led a clinical trial testing the use of nutritional supplements to prevent the need for cataract surgery in seniors.
“Age-related cataract, the leading cause of blindness worldwide, is a leading cause of visual impairment in the United States. The prevalence of age-related cataract is increasing, with an estimated 30.1 million Americans likely to be affected by 2020,” said the study authors.
Previous studies on the use of nutritional supplements to protect the eyes from age-related cataracts have produced mixed results, according to the study authors. The first AREDS clinical trial tested the use of vitamins C and E, beta-carotene, zinc and copper for both age-related macular degeneration and cataracts.
The results of the first AREDS trial showed a 25 percent reduction in the development of advanced age-related macular degeneration. The first AREDS trial did not show any effect on the progression of cataracts.
Lutein and zeaxanthin are antioxidants found in fruits and vegetables. Those two antioxidants have also been shown to collect in the human eye lens.
The researchers for this study set out to test whether the antioxidant qualities in these supplements could reduce the oxidation in the eye lens that clouds the lens and results in cataracts.
For the AREDS2 clinical trial, the researchers recruited 3,159 people between the ages of 50 and 85 who were at risk for age-related macular degeneration.
The participants were split into four groups: 787 were given 10 mg of lutein and 2 mg of zeaxanthin, 803 were given 350 mg of docosahexaenoic acid (DHA) and 650 mg of eicosapentaenoic acid (EPA), 794 received all of the supplements (lutein, zeaxanthin, DHA and EPA) and 775 were given a fake dose of supplements. DHA and EPA are omega-3 fatty acids.
The participants were enrolled in the study for an average of five years. Upon request, 89 percent of the participants were given a multivitamin called Centrum Silver to take daily.
By the end of the study, only 80 percent of the participants reported taking the study-issued supplements 75 percent of the time.
The results showed that 30 percent of participants developed a cataract in at least one eye and 23 percent had to have cataract surgery sometime during the study period. There were no difference found between the rates of cataract surgery between participants who took the lutein/zeaxanthin supplements and those who did not.
The rates of cataract surgery were not different for participants who took DHA/EPA omega-3 fatty acids compared to people who did not take those supplements.
No negative effects were reported in patients who took any of the supplements.
“Daily supplementation with lutein/zeaxanthin had no statistically significant overall effect on rates of cataract surgery or vision loss,” concluded the study authors.
One limitation, noted by the authors, had to do with the group of people in the study being well educated and having a high probability for consuming a high-quality diet, which means that the use of supplements may have had a greater impact on a group of people with low-nutrition diets.
“This is a well-designed study which provides important information on the effectiveness of the micronutrients lutein/zeaxanthin in preventing cataracts. Unfortunately, the study does not offer hope that the use of lutein/zeaxanthin when taken as dietary supplements prevents cataracts,” said Christopher Quinn, OD, FAAO.
“Good scientific evidence such as this is important in helping guide consumers in understanding the health related limitations of dietary supplements,” said Dr. Quinn, who was not involved with this study.
This study was published in May in JAMA Ophthalmology.
The National Eye Institute and several components of the National Institutes of Health provided funding for this study. Alcon, Bausch and Lomb, DSM and Pfizer provided the medications and raw materials for this study. No conflicts of interest were declared.