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Fish-oil supplements no better than placebo at relieving dry eye, study finds

Dry eye is most commonly treated with over-the-counter or prescription artificial tears, as well as medications that reduce inflammation.

Omega-3 fatty acid (fish oil) supplements are no better than placebo at relieving the symptoms of dry eye, according to a study published online last Friday in the New England Journal of Medicine (NEJM). 

About 14 percent of adults in the United States, have dry eye, a condition that occurs when the eyes produce poor-quality or low amounts of tears, which are needed to keep the eyes lubricated. Dry eye can cause a burning, itching or stinging sensation in the eyes, as well as visual problems that can interfere with reading, computer use, night driving and other routine activities.

Dry eye is most commonly treated with over-the-counter or prescription artificial tears, as well as medications that reduce inflammation. Many eye doctors recommend omega-3 fatty acid supplements as an “add-on” treatment for dry eye, not because there has been any good evidence to support that practice, but because omega-3 fatty acids are believed to have anti-inflammatory properties and because they are not associated with any significant side effects.

The new JAMA study — a randomized, double-blinded, controlled clinical trial, which is considered the “gold standard” for evaluating the effectiveness of a medical treatment — now throws that add-on practice into serious question. 

“We were surprised that the omega-3 supplements had no beneficial effect,” said Dr. Vatinee Bunya, one of the study’s authors and an ophthalmologist at the University of Pennsylvania, in a released statement. “The results are significant and may change the way a lot of ophthalmologists and optometrists treat their patients.”

The study’s results also underscore (again) just how overhyped — and oversold — dietary supplements have become in this country. As a news release from the National Eye Institute, which funded the current study, points out, Americans spend more than one $1 billion annually on fish-oil supplements alone. People take them not only to relieve the symptoms of dry eye, but also to reduce their risk of a long list of other ailments, including heart disease, dementia, rheumatoid arthritis and depression. 

Yet research has found no good evidence to support such health claims. 

Study details

The current study, which was conducted at 27 eye centers across the country, involved 535 people who had been diagnosed with moderate to severe dry eye for at least six months. The patients were randomly assigned to take either a daily capsule of omega-3 fatty acids or an olive oil placebo. The capsule with the omega-3 fatty acids contained a combination of 2,000 milligrams of eicosapentaenoic acid (EPA) and 1,000 milligrams of docosahexaenoic acid (DHA).  (According to the NEI, this is the highest amount of omega-3 fatty acids ever tested for the treatment of dry eye.) The placebo capsule contained 5 grams, or about 1 teaspoon, of olive oil.

Neither the patients nor their doctors knew which capsule they were taking.

The patients were told they could continue using any previous treatments they had been prescribed, such as artificial tears and anti-inflammatory medications. 

After 12 months, both groups reported improvements in their symptoms, but there was no difference between the groups. Among the people taking the omega-3 fatty acid supplements, 61 percent reported that their symptoms improved by at least 10 points on a 100-point scale, compared to 54 percent in the group taking the placebo, a difference not statistically significant, according to the researchers.

The study also found no differences in symptom improvement between the two groups based on clinical evaluations of the patients’ eyes by doctors.

“Omega-3 supplements are no more effective than placebo at alleviating dry eye symptoms,” the study’s authors conclude. 

“The findings also emphasize the difficulty in judging whether a treatment really helps a particular dry eye patient,” said Maureen Maguire, one of the study’s authors and director of the Center for Preventive Ophthalmology and Biostatistics at the University of Pennsylvania, in a statement released by the NEI. “More than half the people taking placebo reported substantial symptom improvement during the year-long study.” 

FMI: The study can be read online at the NEJM website.

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