Many people try to treat symptoms of dry eyes by consuming fish oil, either as a supplement or by eating oily fish. Fish oil contains omega-3 fatty acids, which research has shown to have overall health benefits. However, determining whether omega-3s can help specifically treat dry eyes requires more research.

There is some evidence that fish oil may be beneficial for managing dry eyes. People may take fish oil as a supplement, either in capsule or liquid form. People can also get fish oil by eating oily fish, such as salmon, trout, and tuna.

In this article, we look at whether fish oil is an effective and safe treatment for dry eyes, as well as dosage recommendations.

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Fish oil contains the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

According to the National Center for Complementary and Integrative Health, DHA is important for proper functioning of the brain and eyes. Researchers are still investigating whether omega-3 fatty acids can help to treat conditions that affect the brain and eyes.

According to the American Academy of Ophthalmology (AAO), omega-3 oils may improve the function of the meibomian glands. The meibomian glands produce the oily layer in tears.

Problems with the oily layer of tears can lead to dry eyes, as the oily layer prevents the water layer of tears from evaporating, keeping the eyes hydrated.

The AAO also states that the omega-3s present in fish oil may reduce inflammation. Inflammation of the eyelids or front surface of the eye can make dry eye worse, so fish oil may improve symptoms.

People may take fish oil as a supplement, either as a capsule or in liquid form.

People can also consume fish oil through eating fish high in omega-3 fatty acids, such as:

  • salmon
  • sardines
  • herring
  • albacore tuna
  • mackerel
  • lake trout

Flaxseed oil also contains an omega-3 called alpha-linolenic acid (ALA). Flaxseed oil only contains ALA, not EPA or DHA. The liver converts ALA into EPA and DHA.

According to the National Institutes of Health (NIH), the body is only able to convert ALA into around 15% of EPA and DHA. The NIH recommends that consuming EPA and DHA from food sources or supplements is the only way to increase fatty acid levels in the body.

If people do not want to consume any fish products, they may choose to take an omega-3 supplement derived from algae. According to the NIH, algal oil provides around 100-300 milligrams (mg) of DHA, and may contain some EPA as well. Algal oil may provide the body with a similar amount of DHA to eating cooked salmon.

A 2016 study looked at the effects of EPA and DHA on dry eyes in 105 people over the course of 12 weeks. The study found that EPA and DHA supplementation resulted in a significant improvement in dry eye symptoms compared to a placebo of linoleic acid.

Other research referenced in the study also suggests that omega-3 in fish may help relieve dry eyes. In a study of 32,470 females, researchers found that females who had 5-6 servings of tuna each week had a 66% reduction in dry eye disease than females who had 2 servings per week or fewer.

According to the AAO, omega-3s may also help lower the risk of abnormal blood vessels growing, which happens in retinal conditions such as age-related macular degeneration.

However, a 2018 NIH study found omega-3 supplements were no more effective than a placebo for treating chronic dry eye symptoms. The study included 535 participants who had experienced moderate to severe dry eye for at least 6 months.

In the omega-3 group, 349 participants received 2000 mg of EPA and 1,000 mg of DHA. According to the study, this dosage was the highest that researchers have used in a test for treating dry eye disease. In the placebo group, 186 people received olive oil in identical capsules to the omega-3s.

The study found no significant differences in improvement of dry eye symptoms between the two groups.

Fish oil may pose some risks for certain people. If people are taking Warfarin or another blood-thinning medication, they will need to check with a doctor before taking omega-3 supplements. This is because fish oil can interact with these medications and may affect blood clotting.

Children and anyone who is pregnant, breastfeeding, or chestfeeding may also need to check with a healthcare professional before taking fish oil or eating certain types of fish. This is because certain fish contain high levels of mercury.

According to the American Heart Association (AHA), fish that contain high levels of mercury include:

  • shark
  • swordfish
  • king mackerel
  • tilefish

Fish and shellfish with low levels of mercury include:

  • shrimp
  • canned light tuna
  • salmon
  • pollock
  • catfish

The AHA recommends people eat at least 2 servings of fatty fish each week. One serving is 3.5 ounces of cooked fish, or ¾ cup of flaked fish.

According to the NIH, long-term intake of up to 5 grams (g) per day of combined EPA and DHA appears to be safe. The U.S. Food and Drug Administration (FDA) does not recommend consuming more than 3 g per day of combined EPA and DHA, and up to 2 g from supplements.

If people take high doses, such as 900 mg of EPA and 600 mg of DHA per day for several weeks, it may suppress inflammatory responses in the body and decrease the function of the immune system.

So far, the research is inconclusive on whether fish oil can help treat or prevent symptoms of dry eyes.

Some research suggests that increasing omega-3 intake can help improve symptoms of dry eyes. Other research found no significant difference between fish oil and a placebo in improving dry eye symptoms.

Researchers still need to carry out further studies to find consistent evidence for whether fish oil can help in the treatment of dry eyes.

Fish oil contains the omega-3s EPA and DHA. Some research suggests increased intake of these omega-3s could help to relieve dry eyes. There is currently not enough evidence to support this though.

People can make sure they have enough intake of EPA and DHA through food sources, or talk to a healthcare provider about taking a dietary supplement.