Omega-3 are polyunsaturated fats that are found in cold water fishes, such as salmon and mackerel, as well as nuts, like walnuts and flaxseed. These fats help prevent cardiovascular disease and may help keep eyes healthy. Yet, there is a limit to their benefits.
A study sponsored by the National Eye Institute (NEI) suggested that the omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may prevent eye diseases such as diabetic retinopathy. The study, led by Lois Smith, M.D., Ph.D., professor of ophthalmology at Harvard Medical School, Children’s Hospital Boston, shows that a by-product of DHA, known as 4-hydroxy-docoshaexaenoic acid (4-HDHA) prevents abnormal blood vessel growth in the retina, which is seen in diseases like diabetic retinopathy.
The study was done on laboratory mice. The mice were exposed to air containing high levels of oxygen and they were fed omega-3 fatty acids. The high exposure of oxygen leads to abnormal blood vessel growth that is similar to many eye diseases. The omega-3 fatty acids eaten by the mice were converted into enzymes. These enzymes prevented abnormal blood vessel growth in the retina. Researchers wanted to find the specific enzyme that prevented abnormal blood vessel growth in the retina by experimenting on mice who have been engineered not to have one or more of the enzymes that convert omega-3 fatty acids.
Researchers found that abnormal blood vessel growth happened in one mouse and that mouse didn’t have the enzyme known as 5-lipoxygenase (5-LOX). This enzyme converts DHA into 4-HDHA. It is 4-HDHA that prevents abnormal blood vessel growth in the retina. This study demonstrates how eating more cold water fish and taking omega-3 supplements can help prevent abnormal blood vessel growth in the retina.
While omega-3 supplements can prevent abnormal blood vessel growth in the retina, they aren’t good for all eye ailments. Another study funded by NEI looked into the use of omega-3 supplements for the treatment of dry eye. There were 535 people studied who had at least a six-month history of dry eye. Among the participants, 349 people were assigned to receive 3 grams of omega-3 fatty acids in five capsules. The daily dose contained 2000 mg eicosapentaenoic acid (EPA) and 1000 mg docosahexaenoic acid (DHA), which is the highest dose used in a study of dry eye treatments. Those remaining received a placebo of 5 grams daily of olive oil in identical capsules.
Patient symptoms were measured via the Ocular Surface Disease Index, which is a 100-point scale for determining dry eye symptoms, high values represent greater severity and low values represent lower severity. A reduction of 10 points on this index is thought of as significant enough for a person to notice improvement in his or her symptoms.
The participants who reported at least a 10-point improvement in symptoms was 61 percent for the those in the omega-3 group and 54 percent in the control group. Yet the difference between the two groups isn’t statistically significant. The eyes of the study participants were also examined by clinicians who used standardized tests. The amount and quality of their tears was measured, as well as the surface of the eye and no difference in terms of improvement of dry eye was found in both groups.
These studies show that omega-3 is great for cardiovascular disease and diabetic retinopathy, but it doesn’t do much for dry eye.