The long-awaited Age-Related Eye Disease study 2 (AREDS 2) tested omega 3 as well as the carotenoid vitamins lutein and zeaxanthin as additional ingredients to an earlier AREDS formula.
The original AREDS trial tested vitamins C and E together with beta-carotene, also a carotenoid vitamin. The formula also contained zinc. That trial suggested that people who took the supplement were 25 percent less likely to progress to advanced AMD over the five-year study period, compared with participants who took a placebo.
AREDS 2 results, published at the weekend in the US, suggest that adding lutein, zeaxanthin and omega 3 does not improve the original AREDS formula overall.
However the investigators found some benefits when they analyzed two subgroups of participants: those not given beta-carotene and those who had very little lutein and zeaxanthin in their diets.
The AREDS 2 trial also explored changing the dosage of Zinc from the original formula. There was no apparent difference in effect of the lower-dose zinc on the progression to advanced AMD. Rates of reported side effects from zinc were also similar in the two groups receiving different doses. While zinc is an important component of the AREDS supplement it is unclear how much is necessary.
Dr Emily Chew, who led the study said: "When we looked at just those participants in the study who took the AREDS formulation with lutein and zeaxanthin but no beta-carotene, their risk of developing advanced AMD over the five years of the study was reduced by about 18 percent compared with participants who took the AREDS formulation with beta-carotene but no lutein or zeaxanthin."
Dr Chew said that carotenoids can compete with each other for absorption in the body so beta-carotene may have masked the effect of the lutein and zeaxanthin in the overall analysis. Indeed, participants who took all three nutrients had lower levels of lutein and zeaxanthin in their blood compared to participants who took lutein and zeaxanthin without beta-carotene.
Dr Chew said: "Further analysis showed that participants with low dietary intake of lutein and zeaxanthin at the start of the study, but who took an AREDS formulation with lutein and zeaxanthin during the study, were about 25 percent less likely to develop advanced AMD compared with participants with similar dietary intake who did not take lutein and zeaxanthin."
The study also suggests that former smokers, who made up approximately half the study population, were at greater risk of developing lung cancer if they took the preparation which contained beta-carotene. The investigators therefore suggest that beta carotene should be removed from the AREDS formula and replaced with lutein and zeaxanthin. It is already excluded for current smokers.
Helen Jackman, Chief Executive of the Macular Society welcomed the results. She said: "It is clear that AREDS 2 has not found a magic bullet for AMD. But this is a large and complex study and we have yet to have all the analysis of what it means.
“It appears to confirm the findings of the original AREDS study which suggested that the right formula of nutritional supplements can benefit some people with AMD. We may now be able to improve the formula and that is very welcome.
"A healthy diet is important but it is possible that, for those who find that difficult to achieve, supplements may help."
To read a National Eye Institute press release click here.
To read Journal of American Medical Association press release click here.
To read a Royal College of Ophthalmologists statement click here.