Krill Oil Improved Osteoarthritic Knee Pain in Adults with Mild to Moderate Knee Osteoarthritis

by | Oct 6, 2023 | 2022, Arthritis, Fish Oil Supplements, Joint Health

Written by Marlene Hollick, R.D., Ed.D. Based on a randomized, double-blind, placebo-controlled study exploring the effects krill oil supplements on relief of osteoarthritis-related knee pain, results demonstrated that krill oil could improve knee pain scores, knee stiffness, and physical functioning.

joint healthOsteoarthritis develops when joint cartilage is progressively lost, resulting in reduced function and chronic pain. The primary cause of osteoarthritis is damage from mechanical stressors when the body is unable to properly repair damaged joints1. The most common type of osteoarthritis is knee osteoarthritis, with its prevalence increasing with age2. Non-surgical treatments generally involve the use of NSAIDs (non-steroidal anti-inflammatory drugs)3. Long term use of NSAIDS, however, is associated with adverse side effects. One safe alternative is the use of krill oil supplements, based on its omega-3 fatty acid composition associated with anti-inflammatory activity4,5.

The sea crustacean krill (Euphausia superba) is rich in long chain omega-3 polyunsaturated fatty acids (PUFAs) containing phospholipids, compared to the triglyceride composition more commonly found in fish oil6. In addition, krill contains astaxanthin, an antioxidant believed to possess anti-inflammatory characteristics7 8.

To examine how well krill oil worked for relief of osteoarthritis-related knee pain, four sites in Australia were selected for trials with advertisements and social media used to recruit participants. Criteria included gender, age between 40-65, diagnosed osteoarthritis of the knee with pain levels being self-reported. Restricted drugs were avoided by participants.

A six-month randomized, placebo-controlled, double-blind, multicenter phase II trial was designed for the study. The participants were randomly assigned to treatment groups. All participants, statisticians, and staff were blinded to the treatment groups until after completion of the statistical analyses of the data.

The krill oil selected for the study was the “Swisse High Strength Deep Sea Krill Oil”, which contained 1 gm of krill oil per capsule. Each gram of krill oil (E. superba oil) consists of 0.15 gm EPA, 0.07 gm DHA, and 0.11 gm astaxanthin. The gelatin capsule was black and oblong, with the placebo designed to match in appearance and odor. The placebo consisted of 1 gm mixed vegetable oils, lacking the EPA or DHA components.

Randomly assigned participants consumed four capsules daily of either the krill oil or the placebo. Dosage selection for the krill oil, at 4 grams/day, was designed to be higher than those used in prior knee osteoarthritis studies to help promote an anti-inflammatory response. To assess the study outcomes, fasting venous blood samples were obtained from all participants. These blood samples were analyzed for total cholesterol, HDL, triglycerides, and hsCRP; LDLs were calculated. An Omega-3 Index analysis was also performed to determine the quantities of DHA and EPA as a percentage of the total fatty acids in the red blood cells.

Based on the study design 238 participants would be required, with 119 in each treatment group and an allowed dropout rate of approximately 20%9. The level of statistical significance was 0.05, two-sided. Of 465 participants screened, 234 were randomly assigned to treatment groups and received interventions, with 117 receiving the krill oil and 117 receiving the placebo. Participant compliance was determined to be excellent, exceeding 80% over the six-month period.

The results of the study were as follows:

  • Krill oil showed Omega-3 Index increases (from 6.0% to 8.9%) compared with the placebo (from 5.5% to 5.4%), at P<0.001.
  • Krill oil showed knee pain score improvements at six months in both groups, with greater improvements for krill oil than for placebo, at P=0.04. There were no statistically significant differences found at three months.
  • Krill oil showed greater knee stiffness and physical function improvements at six months compared with the placebo, at P<0.05.
  • There were no statically significant differences between the groups regarding NSAID use, serum lipids, and inflammatory and safety markers. The estimated treatment effects were greater for the high-inflammatory group compared to the low- and medium-inflammatory groups, using serum hsCRP as the marker.

Results demonstrated that in adults with mild to moderate knee pain, krill oil was safe to consume and provided modest reported improvements. Limitations of the study included reliance on subjective, self-reported pain assessments instead of objective markers such as cartilage volume measured by an MRI. MRI use could also have provided additional information regarding mechanisms by which krill oil reduced osteoarthritic knee pain.

Source: Stonehouse, Welma, Bianca Benassi-Evans, Jana Bednarz, Andrew D. Vincent, Stephen Hall, and Catherine L. Hill. “Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: a 6-month multicenter, randomized, double-blind, placebo-controlled trial.” The American journal of clinical nutrition 116, no. 3 (2022): 672-685.

© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society for Nutrition. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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Posted October 5, 2023.

Marlene Hollick, Ed.D., M.P.H., M.A., R.D, has decades of hands-on experience and academic expertise across a wide range of health and nutrition disciplines, including home care, hospitals, nursing homes, public schools, and higher education. Dr. Hollick earned her Ed.D. in Higher Education Leadership and Health Care Education from Nova Southeastern University, a Master of Public Health from New York University, and a Master of Arts in Food and Nutrition, also from NYU.  She is a Registered Dietitian, a Certified Dietitian/Nutritionist, and is currently enrolled in the post-graduate Science Writing program at Johns Hopkins University.

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