Fish oil is fantastically good for us, bringing, among other things, clear benefits for heart and brain health.
But adding to prior human and animal evidence in favor of krill oil, another study gives it an edge over its “sister” supplement, in a seemingly critical context.
A Norwegian study in lab mice found that krill oil beat fish oil pretty soundly, in terms of beneficial effects on genes that control blood fat and sugar profiles.
Compared with fish oil, krill oil produced a uniquely broad and beneficial pattern of “nutrigenomic” influences on genes in the liver that control blood fat, sugar, and cholesterol profiles … probably because of the uncommon form in which krill oil's omega-3s occur.
Despite the changes in gene expression, no changes were seen in the animals' blood fat, sugar, or insulin levels.
Krill oil's uncommon omega-3s
The two major omega-3 fatty acids in krill oil (EPA and DHA) are the same two found in fish and in human cell membranes.
However, unlike fish oils, most of the omega-3s in krill oil occur in phospholipid (foss-foh-lipid) form … a difference whose relevance to human health remains unclear.
The human body can use seafood-source omega-3s (EPA and DHA) in any of the three forms in which they occur naturally … triglyceride, phospholipid, and ethyl ester.
While all three omega-3 forms are well-absorbed and comparably beneficial, limited evidence suggests that phospholipid-form omega-3s may be more easily and fully absorbed, compared with triglyceride and ethyl ester omega-3s.
This preliminary evidence fits with evidence that – compared with omega-3 triglycerides and omega-3 ethyl esters – the body needs fewer metabolic steps and less energy to digest, absorb, and distribute omega-3 phospholipids.
And a very small amount of early animal and clinical research suggests that krill oil's phospholipid-form omega-3s may yield superior cardiovascular and other health effects.
As the authors of the new study said, “This research builds upon the body of evidence supporting the theory that phospholipid-bound EPA and DHA are utilized more effectively. However, further research is necessary to explain why there is a difference between these two molecular forms of the beneficial fatty acids.”
However, it's too soon to conclude that krill oil's omega-3s deliver more concrete health benefits than the omega-3s found in fish oils.
However, this is not surprising because, as the authors explained, the mice were young and fed a low fat diet.
Benefits flow from unique gene effects of krill oil's rare omega-3 profile
In this mouse study, krill oil “down-regulated” liver-cell genes that tend to raise levels blood sugar (glucose), fats, and cholesterol.
Significantly, fish oil did not yield equally promising effects, either in terms of the number of genes affected, or the ones affected.
The authors made the key point: “Overall, the data provides support for a role of krill oil in ameliorating [blood chemistry] abnormalities seen with obesity and insulin resistance [pre-diabetes].” (Barger JL et al. 2011)
Still, as they stressed, only human studies can test whether the gene expression patterns that krill oil produce in mice also apply to people.
And only clinical trials can tell whether krill oil bests fish oils at reducing risk factors (and actual risks) for the major metabolic disorders: diabetes, cardiovascular disease, and dementia.
Krill oil shows more gene-based promise for metabolic health
The U.S.-Norwegian team divided lab mice into three groups. Each group was fed the same mouse chow, but with a different oil composition:
Soy Oil (4%)
Fish Oil (1.1% fish oil, 2.9% soybean oil)
Krill Oil (1.5% krill oil, 2.5% soybean oil)
Before and after the trial, the researchers recorded the status – up-regulated (active) or down-regulated (quiet) – of 20,118 genes in the mice (Barger JL et al. 2011).
After three months of feeding, the status of 4,892 genes was altered in the krill oil group, compared with only four percent as many genes (192) in the fish oil group.
Of the 51 similar genes that were changed in both groups, 44 genes were changed in the same way (up-regulated or down-regulated) in both groups.
Not too surprisingly – because fish oil is known to slightly raise blood levels of LDL cholesterol – the genes for cholesterol synthesis were up-regulated in the fish oil group of animals.
(Researchers agree the overall effects of fish oil on people's blood fat profiles – lower levels of triglycerides and of all non-HDL or “good” cholesterol – are highly desirable.)
As the team wrote, “Surprisingly, an [equivalent] dose of EPA and DHA derived from fish oil modulated fewer [genetic] pathways than a krill oil-supplemented diet …”
Perhaps more importantly, the genes affected by krill oil were more pertinent: “… [fish oil] did not modulate key metabolic pathways regulated by krill oil, including glucose metabolism, lipid metabolism and the mitochondrial respiratory chain”. (Barger JL et al. 2011)
(The mitochondrial respiratory chain is the cellular “machinery” that makes energy from glucose and other food factors.)
There are good reasons why fish oil and krill oil would produce different nutrigenomic influences … see our sidebar, “Krill oil's uncommon omega-3s”.
The research team included scientists from Norway's University of Bergen, Norwegian krill oil supplier Aker Biomarine, and a Wisconsin-based genomics lab, so there are clear conflicts of interest.
We chose Aker krill oil for Vital Red™ because it comes from the first krill harvest ever awarded a certification of sustainability … in 2010, by the Marine Stewardship Council.
Banni S, Carta G, Murru E, Cordeddu L, Giordano E, Sirigu AR, Berge K, Vik H, Maki KC, Di Marzo V, Griinari M. Krill oil significantly decreases 2-arachidonoylglycerol plasma levels in obese subjects. Nutr Metab (Lond). 2011 Jan 30;8(1):7.
Barger JL, Berge K, Burri L and Berge R (2011). Differential effects of krill oil and fish oil on the hepatic transcriptome in mice. Front. Gene. 2:45. doi: 10.3389/fgene.2011.00045. Accessed at http://www.frontiersin.org/nutrigenomics/10.3389/fgene.2011.00045/abKstract