Krill oil relieves pain in adults with knee osteoarthritis

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, regular 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 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 score improved in both groups, but the improvements were greater 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 proresolving lipid mediator compounds including resolvins, protectins, and maresins,” they added. [Biochimie 2020;178:105-123; J Clin Rheumatol 2017;23:330-339]

In terms of 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 diarrhoea), 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.