Fish-to-Krill isn’t exactly Apples-to-Apples
Krill oil has hit the Omega-3 supplement market as an alternative to fish oil, touting claims of better absorption. But is it really true? A recent re-examination of the evidence challenges these assumptions.
Salem & Kuratko re-analyzed several reports comparing bioavailability of DHA & EPA from krill oil to that of fish oil (full disclosure: the authors are DSM scientists). Looking at the studies together as a whole, they discovered some interesting points about the available data. Considering that we’re talking about bioavailability of DHA & EPA, a surprising finding was that…
1) No currently published studies have compared equal doses of DHA & EPA in krill oil and fish oil.
Something many don’t realize is that the available concentration of DHA & EPA – the omega-3 fatty acids found in both oils which benefit your health – differs between both krill and fish oil. Generally speaking, krill oil provides less DHA & EPA by volume as compared to fish oil. So when investigators compare equal doses of krill oil to fish oil, it’s not a true “apples-to-apples” comparison since the concentrations of DHA & EPA can differ. Which brings us to our second point…
2) The “krill is more bioavailable” argument is questionable.
The argument of many of the studies comparing krill to fish oil is that if providing a lower dose of EPA & DHA in krill oil relative to fish oil results in a statistically equivalent (that is, not statistically significantly different) rise in the blood concentration of EPA and DHA, then krill oil must be more bioavailable. Makes sense, right? Well, there’s a little bit of sleight of hand going on here. In order for this to be true, then the difference in the amount of DHA & EPA found in the krill oil compared to fish oil would have to be big enough to produce a significant effect rather quickly (which of course, it’s not). In essence these studies are done backwards – they provided different amounts of DHA & EPA from the start of the study and found them to be the same at the end, rather than providing the same amount of DHA & EPA from the start and finding a difference at the end. See? Sleight of hand.
Speaking of sleight of hand, what’s the supposed magic secret behind krill oil anyway? Krill proponents argue that because the omega-3’s found in krill oil are in phospholipid form (as opposed to triglyceride form which is found in fish oil), that allows the body to use the DHA & EPA found within more efficiently. Which brings us to our final point…
3) DHA & EPA in krill oil isn’t all phospholipid bound.
The concentration of DHA & EPA that is bound to phospholipids in commercial krill oil products varies wildly. A recent study found that anywhere from as little as 19% to up to 81% of DHA & EPA in commercial krill oil is phospholipid bound. A large part of the remainder comes from triglycerides, just like fish oil.
So in the end, are the DHA & EPA in krill oil better absorbed than those from fish oil? Right now, it’s safe to say from the available evidence that it’s doubtful. Maybe when scientists do a true “apples-to-apples” (er, “fish-to-fish”?) comparison of bioavailability from both forms, we can finally put this issue to rest.
Salem N, Kuratko CN. A reexamination of krill oil bioavailability studies. Lipids Health Dis 2014 (epub ahead of print).
Araujo P, et al. Determination and structural elucidation of triacylglycerols in krill oil by chromatographic techniques. Lipids 2014; 49(2): 163-172.