It’s hard to miss the media hubbub about the potential health benefits of the omega-3 fatty acid called docosahexaenoic acid (DHA). Research has suggested that DHA in your diet is good for preventing and treating cardiovascular diseases, neurological conditions, depression and a slew of other conditions and maladies, including those that affect the retina.
You can get DHA from eating coldwater oceanic fish, such as salmon, tuna, herring and sardines, as well as from vegetarian sources, including walnuts and flax seed. Fish-oil and vegetarian DHA supplements are also available at most supermarkets and drug stores.
DHA’s Role in Health
So why is DHA thought to be such a powerful nutrient? Before birth and during infancy, DHA plays an essential role in the development of the entire nervous system, including the brain and retinas. Early in life, we get DHA while in the womb, and later from breast milk. (Infant formula is often supplemented with DHA.)
As we develop and mature, we get DHA from our diet. It continues to be critical to the structure, function and health of all cells of the body — especially cells called neurons, which transmit electrical information to and from the brain.
So can DHA help save vision for people affected by retinal diseases? While much of the research is ongoing, there is evidence that it can for some conditions. In another year or two, we are likely to know more about its potential for doing so.
We do know that DHA is prevalent in the retina. In fact, our photoreceptors, the neuronal cells that make vision possible, have more DHA than any other cells in our body. We also know that healthy levels of DHA in photoreceptors maximize retinal function and protect against damage from bright light exposure and oxidative stress. The latter is increased in people with age-related macular degeneration (AMD), retinitis pigmentosa (RP) and virtually all other retinal degenerative diseases.
DHA for Retinitis Pigmentosa
Dr. Eliot Berson, of the Massachusetts Eye and Ear Infirmary, was one of the first clinical researchers to prescribe DHA for a retinal disease. In 1993, he reported that vitamin A palmitate supplementation slowed vision loss in people with RP.
In subsequent studies, he found that eating coldwater fish rich in DHA boosted the vision-preserving effect of vitamin A palmitate. Information on Dr. Berson’s recommended treatment regimen, which also includes lutein supplementation, is available in a newly updated informational document posted on the Foundation’s website.
Drs. David Birch and Dennis Hoffman, clinical researchers at the Retina Foundation of the Southwest, are wrapping up a five-year clinical trial of DHA supplementation for people with X-linked RP. Results from that study should be available in 2013.
DHA for AMD and Autosomal Dominant Stargardt Disease
There is also preliminary evidence that DHA may reduce the risk of vision loss from AMD. In the first age-related eye disease study (AREDS) conducted by the National Eye Institute, researchers saw a correlation in fish consumption with reduced risk of advanced AMD.
The second AREDS (AREDS2) is evaluating the effects of DHA — and a related omega-3 fatty acid called eicosapentaenoic acid, or EPA (also abundant in coldwater fish) — on advanced AMD risk. Many scientists believe that the combination of DHA and EPA is more effective than DHA alone. Results from AREDS2 are expected in 2013. (Antioxidants were also part of the first AREDS and are being evaluated in AREDS2, but I will save that discussion for another blog post.)
And, last, Dr. Paul Bernstein, at the University of Utah, is conducting a clinical trial of DHA and EPA supplementation for people with autosomal dominant Stargardt disease, a form of juvenile macular degeneration caused by mutations in the gene ELOVL4. He plans to report results in 2013.
Consulting a Physician
I’ve covered the major retina-related clinical studies and findings on DHA and EPA, but it isn’t an exhaustive list. Regardless of the disease, or other research reports out there, I urge anyone with a retinal disease to talk to his or her eye doctor before taking DHA and EPA supplements. The doctor can suggest optimal doses and, at the same time, ensure that they don’t interact with other medications a patient is taking.