Fish Oil or Krill Oil? Don’t choose. Take both!

While the considerable health benefits of omega-3 fatty acids – especially with regard to the cardiovascular system and the brain – are well established, there is an ongoing debate as to whether fish oil or krill oil is the better omega-3 supplement.  However, while both fish oil and krill oil increase plasma and membrane concentrations of omega-3 fats, there are important differences between the two marine oils in their mechanism of action and sites of action in the body. In a similar manner in which the two predominant forms of vitamin E – alpha and gamma tocopherol – complement each other’s antioxidant effects, fish oil and krill oil provide complementary biological effects in different tissues in the body.

Structural differences between fish oil and krill oil may account for different ways they are taken up by our cells, as well as for different target destinations. In fish, the omega-3 fatty fats (EPA & DHA) are stored as triglyceride (the major storage fat in our body); in krill the majority of these fatty acids are bound to phospholipids. Phospholipid is a type of fat that comprises the membrane of all living cells. This form of omega-3 fat is more “user-friendly” by the body, whereas the triglyceride form must undergo additional processing. Research indicates that this phospholipid structure of krill oil enables the omega-3 fats to be more efficiently absorbed and integrated into cell membranes.

Cardiovascular Health

Decades of research support the cardiovascular benefits of omega-3 fats from cold-water fatty fish (e.g., salmon, tuna, sardines) and fish oil supplements. Large review studies report consistent reductions in serum triglycerides and increases in beneficial HDL cholesterol levels from consuming omega-3 fats. Guidelines from the American Heart Association recommend eating fish and taking fish oil supplements to decrease sudden deaths, lower blood pressure, and decrease arrhythmias.

The powerful anti-inflammatory effects of omega-3 fats derived from fish account for their cardio benefits. By modulating levels of inflammatory chemicals called cytokines that circulate throughout the body, fish oil lowers body wide inflammation. While krill oil does not appear to provide a systemic anti-inflammatory effect, it was more effective than fish oil in lowering liver triglycerides (fatty liver) and heart triglycerides in a rat model of obesity and metabolic syndrome. In another study in rats, treatment with krill oil before induction of heart attack resulted in significantly reduced structural and functional changes that normally occur after injury to the heart muscle. While no comparison with fish oil was made in this study, the researchers used krill oil because it had been previously demonstrated to be more effective than fish oil in delivering EPA & DHA into heart phospholipids.

Brain Health

As described in this review, recent findings from numerous studies show brain benefits of omega-3 fats that are just as profound as their cardiovascular benefits. This is not surprising considering the fact that the both the heart and brain have some of the body’s highest concentrations of omega-3 fats. The neuroprotective effects of EPA and DHA have been shown to improve autism, ADHD, depression, cognitive decline and impairment, anxiety, and age-related brain shrinkage.

When you ingest omega-3 fats from diet or supplements, these fats are incorporated into the fatty membranes of your cells, including brain cells. (You are what you eat!). Receptors (“docking stations”) for various neurotransmitters such as dopamine and serotonin are embedded in your brain’s cell membranes. Omega-3 fats, especially from krill oil, can favorably modify the phospholipid composition of cell membranes, making the membranes more fluid and pliable. This facilitates enhanced neurotransmitter-receptor interaction with more efficient cell-to-cell signaling and better brain functioning.

Krill oil, with EPA & DHA packaged as phospholipid, may be preferred over fish oil for brain health.  Phospholipid-bound omega-3 fats as found in krill oil are significantly more bioavailable to brain tissue compared with triglyceride-bound omega-3 fats from fish oil. In a study in elderly men, both fish (sardine) oil and krill oil improved cognitive function, but the krill oil was more effective. In addition, the predominant phospholipid in krill oil is phosphatidylcholine, which is also the primary phospholipid in cell membranes. Phosphatidylcholine can increase brain levels of acetylcholine, a major neurotransmitter that plays an important role in memory and learning.

Bone and Joint Health

While fish oil has been found to be beneficial for osteoarthritis and Rheumatoid arthritis, krill oil is also effective against arthritis, and possibly even more so. In an animal model for arthritis, krill was more effective than fish oil at protecting against joint damage and cartilage erosion by significantly reducing the influx of inflammatory cells into the joint and the synovial membrane lining the joint. This study indicates that krill oil may be more beneficial locally in the joint, while fish oil has more systemic effects via modulation of circulating inflammatory cytokines.

Muscle Health

Interestingly, omega-3 fatty acids, regardless of source, appear to benefit skeletal muscle as well. When ingested, omega-3 fatty acids are appreciably incorporated into the membranes of muscle cells, resulting in pronounced effects on muscle metabolic and physical function. EPA and DHA appear to enhance the sensitivity of muscle to anabolic triggers (e.g., resistance exercise, protein, and insulin) and increase activation of mTOR – the master regulator of muscle protein synthesis (MPS). Studies in adults of all ages have demonstrated that supplementation with a moderate dose (~ 4 grams) of EPA/DHA increased mTOR signaling and enhanced the increase in MPS response to a constant infusion of amino acids and insulin. (See my book, “Hold On to Your Muscle, Be Free of Disease” for references).


The cardiovascular benefits of fish oil have been well documented by numerous studies in recent years. In fact, a prescription version of fish oil (Lovaza) has been approved by the FDA to lower very high triglyceride levels. With high concentrations of the omega-3 fats (EPA and DHA), fish oil is also beneficial for brain health, as well as for bone and joint health. In contrast, krill oil has relatively few studies to support its use. However, even with much less EPA and DHA, krill oil is more bioavailable than fish oil owing to its phospholipid form. Krill oil also comes with astaxanthin, the red-orange pigment in some fish and birds that possesses powerful antioxidant properties.

High-dose omega-3 fats from fish oil provides optimal cardioprotection, while krill oil appears particularly effective for brain health and joint health. Both oils are also helpful for the other major inflammatory disorders, e.g, obesity, metabolic syndrome, and diabetes.

Combining fish oil and krill oil in one product is the ideal way to take advantage of these different and complementary sources of omega-3 fats. Additionally, olive oil combined with fish oil provides a synergistic anti-inflammatory effect greater than placebo or fish oil alone.

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