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Vitamin A Test Results
In 1993, Dr. Eliot Berson and colleagues at The Foundation's Research Center, the Berman-Gund Laboratory for the Study of Retinal Degenerations of Harvard Medical School, published results from a clinical trial, which found that a daily dose of 15,000 IU of vitamin A palmitate on average slowed the course of common forms of retinitis pigmentosa (RP) including Usher syndrome type II. This clinical trial heralded vitamin A as the first sight-saving treatment for RP.
Recently, Dr. Berson and colleagues published results of a 12-year follow-up study evaluating the long-term safety of vitamin A in 146 patients with RP who participated in the original vitamin A clinical trial. These patients were otherwise healthy and between the ages of 18 and 54. The daily doses of vitamin A palmitate for this group of patients ranged between 16,349 IU and 24,318 IU.
After 12 years of supplementation, vitamin A blood levels increased by 18 percent. However, all the patients in this follow-up study had blood levels of vitamin A within the normal range. The patients also showed no clinical symptoms or signs of liver toxicity attributable to vitamin A. The study authors conclude, "Prolonged daily consumption of less than 25,000 IU of vitamin A can be considered safe for that time and amount in this age group."
While the long-term safety of vitamin A palmitate in healthy adults is now better established, Dr. Berson recommends that before beginning the vitamin A therapy, patients consult their physician to review their medical history and current health status. As a precaution, patients should also have blood tests to measure vitamin A levels and liver function tests prior to beginning the treatment and annually thereafter. If liver function tests reveal any abnormalities, cessation of vitamin A would be expected to prevent any possible complications due to vitamin A toxicity. This long-term safety study, published in the April 1999 American Journal of Clinical Nutrition, now provides patients and doctors with more complete medical information regarding the safety of the vitamin A treatment for RP.
If you have questions regarding the vitamin A treatment, The Foundation publishes a free booklet entitled, Vitamin A treatment for Retinitis Pigmentosa. The Foundation also distributes a list of mail order companies that provide vitamin A palmitate in 15,000 IU capsules. (T. Hoglund)
Date last modified January 23, 2000