You Asked


Dr. Ockene answers:

Krill are tiny shrimp-like creatures that exist by the billions in the Antarctic sea. As with fish, they eat plankton, which are the source of omega-3 fatty acids. The oil from these creatures contains omega-3 fatty acids just as fish oil does. In addition, the makers claim that additional benefits are derived from antioxidants contained in this oil.

There are four issues here: what is the evidence that Krill oil is of benefit? Has it ever been directly compared to fish oil? What is its omega-3 content? And what evidence is there that the antioxidants in Krill oil, or for that matter any antioxidants given as supplements, are of benefit? We can take these in order.

What is the evidence that Krill oil is of benefit? And has it ever been directly compared to fish oil?

First, a search through Pubmed, the primary national medical literature search service, which lists approximately 75,000 new references each year, comes up with only 13 articles that mention Krill oil. Of these, four were in mice and rats, one was in isolated rat and human cells, one discussed the use of Krill for changing the color of commercial trout flesh, one looked at how Antarctic seabirds find food, one involved the feeding of Peacock Bass fish, and one had a fellow named Krill as the author of an article that had nothing to do with Antarctic Krill! That left only four studies that had anything to do with the use of Krill oil in human beings. Of these four, one was a study of 90 individuals suggesting that Krill oil improved arthritic symptoms, which has also been shown for fish oil. The second study compared Krill oil and fish oil in 70 individuals with premenstrual syndrome and concluded that Krill oil was superior. The third study, which was the most interesting, compared apparently equivalent doses of Krill oil and fish oil with placebo and concluded that the Krill oil produced superior effects on blood lipid levels in humans. The study was only 12 weeks in duration, and only had 30 individuals in each of the four groups of the study. While very interesting, it is important to understand that this is no more than a pilot study, the results of which would need to be reproduced in studies involving many more patients and much longer periods of time. The fourth human paper was simply a review that described the other papers.

So the evidence that Krill oil is of benefit can only be classified as interesting and needing confirmation. It is important to understand that none of these studies followed people for long periods of time, nor did any of the studies involve people who already have coronary disease or other cardiovascular illnesses. Studies of fish oil have involved many tens of thousands of people followed for years. The largest such study, the GISSI Italian trial of patients who had already suffered a heart attack, involved over 11,000 subjects followed for 3 1/2 years, and showed a 45% reduction in sudden death. So if you have a reason to be taking fish oil, the data in favor of it is overwhelming and taking Krill oil instead would be a huge leap of faith for no good reason.

What is its omega-3 content?

In reality, Neptune Krill oil contains a relatively modest amount of omega-3 fatty acid, approximately 150 mg per capsule. The recommended dose, which is two capsules, containing 300 mg of omega-3 fatty acid, is equivalent to a single CVS capsule in omega-3 content and costs much more. Omega-3 capsules that you can purchase at Trader Joe's would have 500 mg of omega-3 fatty acids in each capsule, and even higher strengths are available at health food stores or online. The generally recommended dose of omega-3 fatty acid is 900-1000 mg daily.


Krill oil contains an interesting antioxidant. The problem here is that antioxidants have been extensively studied and there has not yet been a single large-scale study showing that antioxidant supplements are of value. Furthermore, it turns out that the assumption that at least they can't be harmful is not correct. Beta carotene was a very popular antioxidant until it was shown that it did more harm than good. Millions of people took vitamin E without any real evidence that it was of value, until ultimately a number of large-scale, well-done studies showed that it either had no value, or in several studies, produced harm, and in particular seemed to interfere with the very beneficial effect of statin therapy. What the data has shown is that people who eat fruits and vegetables are healthier than those who do not. Knowing that fruits and vegetables contain antioxidants, the assumption was made that taking antioxidants as supplements might be of value. But there is no evidence that this is correct. In fact, it is an extraordinary leap of faith to assume that one can take one of the many dozens of antioxidants present in a fruit, and give it in gross unbalanced excess, and this will be useful!


So the bottom line is that Krill oil may have some special benefit, but only time will tell. At present, there is insufficient evidence to recommend it, especially to those who already have known atherosclerotic disease where fish oil has been shown to be of great benefit. If as a healthy individual you want to take Krill oil instead of fish oil, well, by spending a lot of extra money you will at least be benefiting the economy!