A six year double blind study of 601 RP patients between the ages of 18 and 49 utilizing vitamin A retinyl palmitate was conducted by the Berman-Gund Laboratory for the Study of Retinal Degenerations at Harvard Medical School in Boston. Each year Harvard researchers measured ERG (electroretinogram) values in the group (high ERG scores correlate with healthy photoreceptor cells known as rods and cones), peripheral vision and visual acuity. Data from this study suggests that an RP patient beginning vitamin A therapy at age 32 will retain some useful vision until age 70. This is seven years longer than one taking no supplements.
Vitamin A plays a functional role by attaching itself to a protein in the rods and cones. When exposed to light, the vitamin changes shape - the first step in relaying light detection signals to the brain. But the mechanism by which vitamin A helps the retina disease remains unknown. While the Harvard researchers are now recommending vitamin A therapy for most RP patients, they caution against taking any form except the palmitate - and then only under the care and supervision of an ophthalmologist.
Those subjects taking vitamin E along with vitamin A actually accelerated retinal degeneration. Therefore one would have to assume that RP patients should not take high doses of vitamin E. Those taking vitamin E had lower concentrations of vitamin A in their blood, suggesting that E may inhibit the body's absorption or transport of A.
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