Two Forms of Omega-3 Supplements for Treating Dry Eye Disease
abstract
This abstract is available on the publisher's site.
Access this abstract now Full Text Available for ClinicalKey SubscribersPURPOSE
To assess the efficacy of 2 forms of oral long-chain omega-3 (ω-3) essential fatty acid (EFA) supplements, phospholipid (krill oil) and triacylglyceride (fish oil), for treating dry eye disease (DED).
DESIGN
Randomized, double-masked, placebo-controlled clinical trial.
PARTICIPANTS
This study was conducted at a single site and involved 60 participants with mild to moderate DED who were randomized (1:1:1) to 1 of 3 groups: placebo (olive oil), krill oil, or fish oil supplements.
METHODS
Participants received 1 of the 3 interventions: placebo (olive oil 1500 mg/day), krill oil (945 mg/day eicosapentaenoic acid [EPA], + 510 mg/day docosahexaenoic acid [DHA]), or fish oil (1000 mg/day EPA + 500 mg/day DHA) for 90 days, with monthly study visits.
MAIN OUTCOME MEASURES
Primary outcome measures were mean change in (1) tear osmolarity and (2) DED symptoms (Ocular Surface Disease Index [OSDI] score) between days 1 and 90. Secondary outcomes included mean change in key clinical signs (tear stability, tear production, ocular surface staining, bulbar and limbal redness, tear volume, anterior blepharitis, meibomian gland capping) and tear inflammatory cytokine levels.
RESULTS
In total, 54 participants completed the study. At day 90, tear osmolarity was reduced from baseline with both krill oil (mean ± standard error of the mean: -18.6±4.5 mOsmol/l; n = 18; P < 0.001) and fish oil (-19.8±3.9 mOsmol/l; n = 19; P < 0.001) supplements, compared with placebo (-1.5±4.4 mOsmol/l; n = 17). OSDI score was significantly reduced at day 90 relative to baseline in the krill oil group only, compared with placebo (-18.6±2.4 vs. -10.5±3.3; P = 0.02). At day 90, there were also relative improvements in tear breakup time and ocular bulbar redness, compared with placebo, for both forms of ω-3 EFAs. Basal tear levels of the proinflammatory cytokine interleukin 17A were significantly reduced in the krill oil group, compared with placebo, at day 90 (-27.1±10.9 vs. 46.5±30.4 pg/ml; P = 0.02).
CONCLUSIONS
A moderate daily dose of both forms of long-chain ω-3 EFAs, for 3 months, resulted in reduced tear osmolarity and increased tear stability in people with DED. Omega-3 EFAs in a predominantly phospholipid form (krill oil) may confer additional therapeutic benefit, with improvements in DED symptoms and lower basal tear levels of interleukin 17A, relative to placebo.
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Additional Info
Disclosure statements are available on the authors' profiles:
A Randomized, Double-Masked, Placebo-Controlled Clinical Trial of Two Forms of Omega-3 Supplements for Treating Dry Eye Disease
Ophthalmology 2016 Nov 03;[EPub Ahead of Print], LA Deinema, AJ Vingrys, CY Wong, DC Jackson, HR Chinnery, LE DownieFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
What is the difference between krill and fish oil?
In this small study of people with dry eyes, both fish oil and krill oil were found to be beneficial, but krill oil was superior to fish oil in reducing the levels of IL-17α, an inflammatory cytokine. Krill oil also reduced bulbar redness better than fish oil.
So, what is the difference between fish and krill oil?
Both are long-chain fatty acids that combine eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Krill makes up in numbers for what it lacks in size. This small crustacean makes up the largest biomass on the planet (humans are number 2). Since it is so small and lower on the food chain, it does not contain as many contaminants as larger animals that live in the ocean. Krill products are relatively free of dioxins and PCBs.
If you place a fish oil capsule side by side with a krill oil capsule, you will see that the krill is red in color while the fish oil is a paler yellow. This is because krill contains larger amounts of the red carotenoid, astaxanthin. This is also why wild-caught salmon is redder than farm-raised. Farm-raised fish are fed grains which do not contain astaxanthin. Krill and wild salmon eat astaxanthin-rich plankton and algae. This red carotenoid is more potent than vitamin E, beta-carotene, and lycopene. Like other antioxidants, it has been found to reduce the risk of macular degeneration and prevent ocular damage from UV light.
Another difference between krill and fish oil is the type of fat it contains. Krill oil has more phospholipids and may be better absorbed than the triglyceride-rich fish oil. Astaxanthin is also a fat-soluble vitamin that is better absorbed when consumed with fats.
The down side is that krill oil is much more expensive. A good product can be 0.50 cents/pill pricier. Be careful, as some products that advertise krill oil on the label, contain mainly fish oil.
I am generally leery of nutrients that come in capsules as they often detour from simply eating the foods rich in the nutrients. Although krill and fish oil capsules were found to help dry eyes in this study, eating fish with red, yellow, and orange carotenoid-rich vegetables with a handful of fatty nuts to increase the absorption of the astaxanthin may work just as well. We would need a study that includes a diet arm.
But, if you have a patient with dry eyes and you want to provide a low-harm, beneficial therapy, both krill and fish oil appear to be good options.
The doses of fish oil and krill oil used in this study were similar; 1000 mg of EPA and 500 mg of DHA. Remember, the dose is determined by the amount of EPA and DHA found on the white label and not the amount on the front label of the supplement bottle. Don’t forget to multiply the EPA and DHA content by the dose size. If the white label says 500 mg of EPA and 250 mg of DHA and the dose is 2 capsules, you would need to recommend 4 capsules daily to achieve 1000 mg of EPA and 500 mg of DHA.