Does Health Food Store Product have Beneficial Effects in Retinitis Pigmentosa?

July 9, 2013 - Israeli scientists have recently published a paper suggesting that a specific type of green algae capsules may have some benefits for some people with retinitis pigmentosa. At this point, their study raises more questions than it answers, but it is an intriguing premise.

People with retinitis pigmentosa in the study were treated for 90 days taking four capsules containing 300 mg of 9-cis beta-carotene–rich alga Dunaliella bardawil each day. Dunaliella is a type of green microalgae often sold as a nutritional supplement in health food stores. The particular type of Dunaliella used in this study, Dunaliella bardawil, is not widely available in North America but can be purchased online.

In total, 29 people with retinitis pigmentosa participated in this study, but not all seemed to benefit. Most of the benefits were seen in a subgroup of ten patients. These patients reported some improvements in their night vision and had measurable improvements of retina function as assessed with an electroretinogram (ERG). This test measures the retina's electrical response to light. The researchers speculate that the treatment is likely most useful for people with specific genetic types of retinitis pigmentosa, although the particular types have not yet been identified.

Dunaliella is very rich in 9-cis beta-carotene - a specific form of vitamin A. Beta-carotene is part of the chemical process within the retina that allows us to process visual signals. The authors of the paper speculate that this specific form of beta-carotene may help damaged photoreceptors function in some types of retinitis pigmentosa.

Dr. Orson Moritz of the University of British Columbia also studies the ways that the retina processes light. He notes that the authors of this study are appropriately cautious about the reporting their results, warning that there in not enough evidence in place to recommend this therapy. He also notes that it is not clear that this effect is particular to people with retinitis pigmentosa. The study does not look at how the supplements might affect the ERGs of people with normal vision.

Dr. Yves Sauve at the University of Alberta studies nutritional therapies for retinal disease. He is also cautious about this research. He says that ERG results are an important tool to study retinal disease, but that he wishes that their study had also looked at whether or not the supplements made useful changes in a person’s vision (for example whether it affected visual acuity – the ability to read, recognize faces, etc). He also stresses a significant caveat for people thinking of trying this therapy.

“A recent large study of vitamins to treat age-related macular degeneration showed that taking high levels of beta-carotene can increase the lung cancer risk for smokers and ex-smokers,” says Dr. Sauve. “Other studies also support this finding. People who have a history of smoking, regardless of long it has been since they stopped, should not take beta-carotene supplements like the ones used in this study.”

This study of Dunaliella bardawil supplements was published in JAMA Ophthalmology.

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