Study Shows Vitamin A Slows RP
Most adults with blinding retinitis pigmentosa should take a daily 15,000 IU vitamin A palmitate supplement and avoid high dose vitamin E to help prolong their vision.
Most adults with blinding retinitis pigmentosa (RP) should take a daily 15,000 IU vitamin A palmitate supplement and avoid high dose vitamin E to help prolong their vision, based on results from a large randomized clinical trial published in the June 1993 issue of Archives of Ophthalmology.
This recommendation is the first from a well-designed clinical trial indicating that people can be treated for retinitis pigmentosa. Alan M. Laties, M.D., chairman of the Foundation Fighting Blindness' Scientific Advisory Board, said of these findings, "This treatment can be a benefit, a very real one, for people who have retinitis pigmentosa. Although not a cure, it will improve quality of life, potentially adding many years of useful vision. The discovery that vitamin E is of no use, and in fact potentially harmful, is not only important on its own, but further justifies this extensive study."
Eliot L. Berson, M.D., the study's principal investigator and Professor of Ophthalmology at Harvard Medical School, said that adults who supplemented their diets with 15,000 IU of vitamin A palmitate daily had on average about a 20 percent slower annual decline of remaining retinal function than those not taking this dose.
Based on this finding, the investigators estimated that an average patient in the study, who started taking a daily supplement of 15,000 IU vitamin A palmitate at age 32, would retain some useful vision until age 70, whereas a patient not on this dose would lose useful vision by age 63.
The investigators also recommended that adults with retinitis pigmentosa should avoid taking high-dose vitamin E supplements. In the study, the disease appeared to progress faster on average in patients on a daily 400 IU vitamin E supplement than in those taking a trace amount of the vitamin. However, the study showed no evidence that normal dietary or small supplemental amounts of vitamin E have an adverse effect on the disease.
Retinitis pigmentosa is a group of inherited diseases that usually starts with night blindness, followed by progressive loss of peripheral vision. Over a period of years this results in "tunnel vision," and may lead to total blindness. It causes the progressive deterioration of specialized, light-absorbing cells in the retina, the paper-thin tissue that lines the back of the eye like film in a camera. The majority of people with retinitis pigmentosa are legally blind by the age of 40, with a central visual field of less than 20 degrees in diameter. An estimated 1.5 million people worldwide are affected by retinitis pigmentosa.
The carefully designed and monitored clinical trial involved 600 patients with RP between the ages of 18 and 49, who were at different levels of visual function. The six-year study was conducted at a cost of $5 million at the Berman-Gund Laboratory for the Study of Retinal Degenerations at Harvard Medical School, with the support of The National Eye Institute and The Foundation Fighting Blindness.
The investigators stressed that adults considering vitamin A palmitate supplementation should first:
- Consult with their doctor about vitamin A palmitate supplementation.
- Have fasting blood levels of vitamin A measured and liver function tests administered before startin treatment. People with certain pre-existing medical conditions may not be eligible for this treatment.
- Take vitamin A palmitate, since this form of the vitamin was used in the study. Beta-carotene, a natural precursor of vitamin A, is not a predictable source of vitamin A and therefore is not a suitable substitute for vitamin A palmitate.
- Make a point of eating a balanced diet, without selecting foods that are especially high in vitamin A.
- Avoid taking high-dose vitamin E supplements.
Commenting on the results of the vitamin A study, Dr. Berson stated, "One of my biggest concerns is that people will make the mistake of thinking that vitamin A supplementation in excess of the 15,000 IU recommended will provide even greater benefit. We have evidence in fact that supplementation of a regular diet with greater than 15,000 IU of vitamin A does not provide greater benefit. Moreover, a daily vitamin A intake exceeding 25,000 IU over the long-term can be toxic in adults and may cause side effects such as liver disease.
"Our interpretation of the study results is that the course of the common forms of retinitis pigmentosa is slower on average among adult patients on a regular diet who take a daily 15,000 IU vitamin A supplement in the palmitate form compared with the course of those patients not on this supplement."
Because the study involved adults between the ages of 18 and 49, no formal recommendations can be made for patients under the age of 18. Also, women with retinitis pigmentosa should not take 15,000 IU vitamin A palmitate supplements during the time leading up to planned pregnancy and during pregnancy, because high doses of vitamin A have been linked to birth defects.
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 or tablets as the correct dose is not available in most local food stores. Beta carotene is not a suitable substitute for Vitamin A Palmitate in the context of this treatment.
Please check with your doctor before starting this treatment.