March 15, 2007 — Beta-carotene supplementation has neither a beneficial or harmful effect on the risk for age-related maculopathy (ARM), according to the results of a randomized trial reported in the March issue of the Archives of Ophthalmology.
"In some observational studies, individuals who self-select for use of antioxidant nutrients and other dietary intakes have lower risk of ARM," write William G. Christen, ScD, from Harvard University in Boston, Massachusetts, and colleagues. "Evidence from randomized trials is accumulating to evaluate a possible role for nutritional supplement use in delaying disease onset and progression. The Age-Related Eye Disease Study (AREDS) demonstrated that treatment with high-dose antioxidant supplements (ascorbic acid, vitamin E, and beta carotene) and zinc could mitigate the progression to advanced ARM in persons at high risk."
The Physicians' Health Study I16 (PHS I), which tested beta-carotene and low-dose aspirin use among 22,071 apparently healthy US male physicians, showed no benefit or harm of 12 years' use of beta-carotene treatment on risk for cancer or cardiovascular disease. This analysis describes the results for ARM from the randomized beta-carotene component of the PHS I.
In this double-masked trial, 22,071 apparently healthy US male physicians aged 40 to 84 years were randomized to receive beta-carotene (50 mg every other day) or placebo. The primary endpoint was incident ARM causing a reduction in best-corrected visual acuity to 20/30 or worse.
After 12 years of treatment and follow-up, there were 162 cases of ARM in the beta-carotene group and 170 cases in the placebo group, yielding a relative risk (RR) of 0.96 (95% confidence interval [CI], 0.78 - 1.20). Findings were similar for secondary outcomes of ARM with or without vision loss (275 vs 274 cases; RR, 1.01; 95% CI, 0.86 - 1.20) and advanced ARM (63 vs 66 cases; RR, 0.97; 95% CI, 0.69 - 1.37).
"These randomized data relative to 12 years of treatment among a large population of apparently healthy men indicate that beta carotene supplementation has no beneficial or harmful effect on the incidence of ARM," the authors write. "Long-term supplemental use of beta carotene neither decreases nor increases the risk of ARM."
Study limitations include a possibly inadequate dosage of beta-carotene, possibly insufficient duration of treatment of 12 years, poor compliance with the assigned treatment, bias in the ascertainment of the endpoints, and confounding by other factors.
"The results of this trial indicate that beta carotene supplementation for 12 years has little effect on the development of visually significant ARM in apparently healthy men," the authors conclude. "These findings, together with forthcoming data from other completed and ongoing trials, will complement the findings in the AREDS by clarifying the effects of individual antioxidant supplements and other nutrient combinations and should help ensure rational clinical and public health recommendations for the prevention of ARM."
The National Institutes of Health (NIH) supported this study. Some of the authors have disclosed various financial relationships with NIH, Harvard University Clinical Nutrition Research Center, DSM Nutritional Products, Inc (Roche), BASF, Cognis, Astra Zeneca, Bristol-Meyers Squibb Company, Merck and Co, Inc, Novartis AG, Bayer AG, DMS Pharmaceuticals, McNeil Consumer Products, Pfizer Inc., PLIVA, Wyeth Pharmaceuticals, GlaxoSmithKline Inc, Nutra Quest International, Inc., Dow Corning Corp, Bayer Health Care, the National Source Vitamin E Association, Procter & Gamble, Actelion Ltd, Actelion Pharmaceuticals Ltd, Agatston Research Institute, Amgen Inc, Chattem, Inc, Delaco Company, the US Food and Drug Administration, Keryx Biopharmaceuticals, Inc., Reliant Pharmaceuticals, LLC, TAP Pharmaceutical Products Inc., United BioSource Corporation, UpToDate, and/or Brigham and Women's Hospital.
Arch Ophthalmol. 2007;125:333-339.Source:
http://www.medscape.com/viewarticle/553647?src=mp
