Krill oil supplement is not only safe to consume but also modestly improves knee pain, stiffness, and physical function in adults with mild to moderate knee osteoarthritis (OA), reveals a study.
On the other hand, “[t]here was insufficient evidence to suggest treatment-related effects with respect to nonsteroidal anti-inflammatory drug (NSAID) usage, any of the serum lipids, or inflammatory or safety markers,” according to the researchers.
This double-blind, randomized, placebo-controlled, multicentre trial was conducted for 6 months and included 235 healthy adults (aged 40‒65 years; body mass index >18.5 to <35 kg/m2) clinically diagnosed with mild to moderate knee OA, chronic knee pain, and taking <0.5 g/d long-chain omega-3 polyunsaturated fatty acids (PUFA).
Participants were randomly assigned to receive either 4-g krill oil/d (0.60 g EPA/d, 0.28 g DHA/d, 0.45 mg astaxanthin/d) or a placebo (mixed vegetable oil). The researchers assessed knee outcomes using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) numeric scale (normalized to scores of 0‒100) at baseline, 3 months, and 6 months.
Supplementation with krill oil increased the omega-3 index relative to placebo (from 6.0 percent to 8.9 percent vs from 5.5 percent to 5.4 percent, respectively; p<0.001). [Am J Clin Nutr 2022;116:672-685]
Knee pain scores improved in both groups, but the improvements were more significant for krill oil than for placebo (difference in adjusted mean change between groups at 6 months, ‒5.18, 95 percent confidence interval [CI], ‒10.0 to ‒0.32; p=0.04).
Krill oil also resulted in greater improvements in knee stiffness and physical function compared with placebo (difference in adjusted mean change between groups at 6 months, ‒6.45, 95 percent CI, ‒12.1 to ‒0.9 and ‒4.67, 95 percent CI, ‒9.26 to ‒0.05, respectively; p<0.05).
In addition, no between-group differences were noted in NSAID use, serum lipids, and inflammatory and safety markers.
“Krill oil is suggested to reduce pain through anti-inflammation mechanisms due to its high content of long-chain omega-3 PUFAs and astaxanthin,” the researchers said. [Biochimie 2020;178:105-123; Molecules 2020;25:5342]
“EPA and DHA influence inflammation through various mechanisms, including modulation of the proinflammatory eicosanoids toward a more anti-inflammatory profile, and through the generation of pro-resolving lipid mediator compounds including resolvins, protectins, and maresins,” they added. [Biochimie 2020;178:105-123; J Clin Rheumatol 2017;23:330-339]
Regarding safety, no between-group difference was observed in the incidence of treatment-related adverse events. Earlier studies with krill oil in OA participants also did not report any treatment-related AEs. [J Am Coll Nutr 2007;26:39-48; PloS One 2016;11:e0162769]
“The current trial did not report treatment-related adverse events previously reported in fish oil trials, including fish-smelling eructation, gastrointestinal disorders (eg, flatulence and diarrhea), or bleeding/vascular complications,” the researchers said. [Ann Rheum Dis 2016;75:23-29; Arthritis Res Ther 2009;11:R192]
OA, a major cause of chronic pain and disability, is typically treated with NSAIDs and analgesics, which may have side effects. Krill oil, which is rich in anti-inflammatory long-chain omega-3 PUFAs and astaxanthin, may be a safe and effective alternative treatment, according to the researchers.