Evidence Review
Bioavailability: krill vs. fish oil
The question of whether krill oil's phospholipid structure actually translates to superior bioavailability has been studied in several small trials. Schuchardt et al. (2011) conducted a randomized crossover trial in twelve healthy men, measuring EPA+DHA incorporation into plasma phospholipids over 72 hours after a single 1,680 mg dose. The mean AUC was 80.03 for krill oil versus 59.78 for re-esterified triglyceride fish oil and 47.53 for ethyl ester fish oil [1]. The authors noted the krill oil also contained approximately 22% of its EPA and 21% of its DHA in free fatty acid form, which may further accelerate absorption. Limitations: n=12, single dose, acute measurement only.
Ramprasath et al. (2013) used a double-blind, randomized crossover design in 24 healthy volunteers given either krill oil or fish oil (each providing 600 mg omega-3 PUFA) or placebo for four weeks. The omega-3 index — considered a better long-term marker than acute plasma levels — increased significantly more in the krill oil group than the fish oil group (p = 0.0143) and versus placebo (p < 0.0001). The n-6:n-3 ratio in plasma and red blood cells also fell more with krill oil. No adverse events were reported [2].
Network meta-analyses pooling data from multiple trials have provided more mixed conclusions, with some finding equivalent bioavailability between the two forms when dose is matched. The field is still working toward consensus.
Inflammation and arthritis symptoms
Deutsch (2007) conducted a 30-day randomized, double-blind, placebo-controlled trial in 90 patients, testing 300 mg per day of Neptune Krill Oil against placebo. C-reactive protein (CRP), a key marker of systemic inflammation, decreased 19.3% in the krill oil group after just 7 days, while CRP increased 15.7% in the placebo group over the same period. By days 14 and 30, CRP reductions in the krill oil group reached 29.7% and 30.9% respectively (p < 0.001). Pain scores improved 28.9% within 7 days (p = 0.050), stiffness by 20.3% (p = 0.001), and functional impairment by 22.8% [3]. The study was small and conducted by the manufacturer's research team, but the magnitude and speed of CRP reduction is striking.
PMS and dysmenorrhea
Sampalis et al. (2003) randomized 70 women with PMS in a double-blind, three-month trial comparing Neptune Krill Oil to fish oil. Women in the krill oil group reported statistically significant improvement across emotional and physical PMS symptoms (p < 0.001), and used significantly fewer pain medications during dysmenorrhea than the fish oil group (p < 0.03). The authors concluded krill oil was more effective than omega-3 fish oil for the complete management of premenstrual symptoms [4]. Mechanistically, the anti-inflammatory pathway — reducing prostaglandin E2 activity via competitive inhibition — is the same as fish oil, but the phospholipid form may reach relevant tissues more readily.
Cardiovascular markers
Results here are more modest. Rundblad et al. (2018) randomized 36 healthy adults to krill oil, fatty fish, or control for 12 weeks. Both the fish and krill groups showed significant increases in plasma marine omega-3 fatty acids versus control (p ≤ 0.0003). The krill group showed a notable blood glucose reduction (5.6 to 5.3 mmol/L, p = 0.01 vs. control), but neither group showed significant differences in total cholesterol, LDL, HDL, or triglycerides compared to control — likely due to the small sample size [6].
A 2014 review by Backes and Howard concluded that evidence supporting krill oil as a first-line cardiovascular intervention is limited, noting that triglyceride-lowering at therapeutic doses (which would require large amounts of krill oil) is better documented for fish oil [5]. For people specifically targeting triglycerides, higher-dose omega-3 concentrates (EPA or EPA+DHA pharmaceutical formulations) are better studied. Krill oil's cardiovascular argument rests more on long-term omega-3 index optimization than acute lipid changes.
Summary of evidence quality
| Use case |
Evidence strength |
| Bioavailability advantage over fish oil |
Moderate — consistent directional signal, small trials |
| Anti-inflammatory / CRP reduction |
Preliminary — one notable RCT, needs replication |
| Joint pain / stiffness |
Preliminary — small trials, some industry funding |
| PMS / dysmenorrhea |
Moderate — RCT showing superiority over fish oil |
| Triglyceride lowering |
Weak — modest effects at typical doses |
| Omega-3 index improvement |
Moderate — crossover trial data supportive |