Beta-carotene dietary supplementation does not prevent the risk or progression of age-related maculopathy (ARM), according to a new study published in Archives of Ophthalmology.

Jeffrey Anshel, O.D., of Carlsbad, Calif., who lectures on nutrition and visual health, is not surprised by the findings. Beta-carotene is not appropriate as the sole source of supplemental vitamin A, which is vital to retina health, he says. Beta-carotene, as pro-formed supplemental vitamin A, does not as readily convert to preformed vitamin A (retinol) in the older population as it does in younger people.

The 12-year study monitored 22,071 healthy American male physicians between the ages of 40 and 84. Participants were randomly assigned to either a treatment or placebo group, and over a span of 12 years, received 50mg of beta-carotene or a placebo every other day. Researchers measured reduction in best-corrected visual acuity as a result of incident ARM.

Upon the trials completion, 162 cases of ARM were found in the beta-carotene group vs. 170 cases in the placebo group.

The researchers concluded that beta-carotene supplements have neither a beneficial nor a negative effect in the incidence of ARM.

Although carotenoids are important for visual health, Dr. Anshel does not agree with the dosage administered in the trial. The amount in the [ARM] study is way over the amount of supplemental beta-carotene necessary to quench the singlet oxygen associated with ARM if other singlet oxygen-quencher antioxidants are available through diet or other supplementation, which they almost always are.

Too much beta-carotene inhibits the absorption of the two xanthophylls (oxygenated carotenoids), lutein and zeaxanthin, which are vital for optimal macula pigment density and UV lens protection.

Since they are all a similar class of carotenoids, excessive beta-carotene will effectively reduce the amount available to the macula and lens, he says.

Dr. Anshel stresses the value of a well-balanced vitamin supplement. There is no one magic bullet supplement that can cure any chronic eye disease, he says.

 

Christen WG, Manson JE, Glynn RJ, et al. Beta Carotene supplementation and age-related maculopathy in a randomized trial of US physicians. Arch Ophthalmol 2007 Mar;125(3):333-9.