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What is krill oil?
Krill are small crustaceans that live in vast shoals in the cold waters of the Antarctic. They measure a few centimetres in length and occupy the very bottom of the marine food chain, feeding on phytoplankton.
This position has a direct impact on the quality of its oil. Marine contaminants (heavy metals, organic pollutants) become concentrated as they move up the food chain. A predator at the top of this chain accumulates what all the lower levels have ingested. Krill, however, is almost at the starting point, which naturally limits its contaminant load.
Its oil provides the same omega-3 fatty acids as fish oil – EPA and DHA – but in a different chemical form, and is accompanied by two compounds not found in conventional fish oil. It is these three differences that make all the difference.
Krill or fish oil: the real differences
The comparison is often presented in a caricatured way, one way or the other. Here is what really sets the two apart.
Phospholipids versus triglycerides
This is the key structural difference. Infish oil, EPA and DHA are bound in the form of triglycerides, or ethyl esters in concentrated versions. Inkrill oil, they are predominantly bound to phospholipids.
Why this matters: phospholipids are the building blocks of our cell membranes. Omega-3s therefore arrive in a form that is already close to the one they will take on in the body. This form is also water-soluble, which aids digestion and explains the better tolerance reported by many users.
Several studies suggest more efficient incorporation into cell membranes at equivalent doses of EPA and DHA. However, we must remain cautious: the exact extent of this benefit is still a matter of debate, and it does not elevate krill oil to a different category of product.
Astaxanthin, the bonus compound
Krill oil naturally containsastaxanthin, a carotenoid pigment that gives it its red colour. It is an antioxidant, and its presence has an immediate practical benefit: it protects the omega-3s from oxidation within the capsule.
This is far from trivial. Polyunsaturated fatty acids go rancid easily, and oxidised oil loses its benefits whilst potentially causing digestive discomfort. Astaxanthin acts as a built-in natural preservative.
Concentration: the argument in favour of fish
This is the point that krill advocates tend to overlook. Krill oil is significantly less concentrated in EPA and DHA than concentrated fish oils.
The practical implication is that, to reach the 250 mg of EPA + DHA required for a health claim, you often need more krill capsules than concentrated fish oil capsules. And as krill oil is more expensive to begin with, the price difference per milligram of omega-3 is significant.
The honest conclusion from this table is that neither option is superior in every respect. Krill holds its own in terms of form, tolerance and built-in antioxidants; fish oil in terms of concentration and price. The choice depends on what you’re looking for, and both fall under the category of omega-3s and fatty acids.
The recognised benefits of omega-3s
An important methodological point: health claims relate to EPA and DHA, not to the source. Whether you obtain them from krill, fish or algae, they are the same molecules and have the same recognised functions.
- EPA and DHA contribute to the normal functioning of the heart, from 250 mg per day
- DHA contributes to the maintenance of normal brain function and normal vision, from 250 mg per day
- EPA and DHA help maintain normal blood pressure and normal blood triglyceride levels, at higher intakes
So be sure to read the label, looking for the amounts of EPA and DHA per daily dose, rather than the total amount of oil. A product labelled ‘1,000 mg of krill oil’ may provide as little as 120 mg of beneficial omega-3s – a fact that the figure highlighted on the label does not reveal.
What omega-3s do not do
Two common misconceptions deserve to be clarified.
Omega-3s are not anti-inflammatories in the medicinal sense. They alter the profile of the mediators that the body produces from fatty acids, which has nothing to do with the action of ibuprofen. When it comes to joint comfort, they form part of a range of factors, amongst which muscle strengthening and mobility remain the most decisive – a point we explore in detail in our article on joint creaking and its solutions.
Omega-3s do not cause weight loss. They are lipids, providing 9 kcal per gram like all others. Their benefits are structural and functional, not slimming.
Dosage, intake and storage
Three practical rules are sufficient to cover the essentials of use.
- Aim for at least 250 mg of EPA + DHA per day to meet the threshold associated with claims regarding heart and brain health. Higher intakes are for specific purposes and should be discussed with a healthcare professional.
- Take the capsules with a meal containing fat. Omega-3s are fat-soluble, and taking them on an empty stomach reduces absorption whilst increasing the risk of acid reflux.
- Store away from light and heat. Polyunsaturated fatty acids oxidise, and rancid oil has lost most of its benefit. A capsule that gives off a strong, unpleasant odour when the bottle is opened is a bad sign.
Over time, omega-3s work in a similar way to vitamin D: they need to be taken regularly over several weeks before there is a measurable change in the composition of cell membranes. A ten-day course has no physiological benefit.
Contraindications and precautions
There is one absolute contraindication that is often overlooked: an allergy to shellfish. Krill is a crustacean. If you are allergic to prawns, crabs or langoustines, you must not take krill oil; instead, opt for fish oil or a plant-based source derived from microalgae.
In other situations, seek medical advice:
- anticoagulant or antiplatelet treatment – omega-3s may affect platelet aggregation
- planned surgery – you are often advised to stop taking it a few days beforehand
- pregnancy and breastfeeding: omega-3s are beneficial, but the choice of product should be made in consultation with a healthcare professional
- knowncoagulation disorders
At usual doses, tolerance is good. The most common side effects are gastrointestinal (belching, aftertaste, loose stools) and are generally alleviated by taking the supplement with a meal.
Frequently asked questions
Is krill oil better than fish oil?
Better in some respects, less so in others. Krill provides omega-3 in the form of phospholipids, contains astaxanthin and causes less heartburn. Fish oil has a higher concentration of EPA and DHA, and is much cheaper per milligram of omega-3.
If your priority is digestive tolerance and budget is not a constraint, krill is the better choice. If you’re looking to achieve a high intake at the best value for money, concentrated fish oil is the more sensible option. And if you’re allergic to shellfish, the question doesn’t even arise.
How much krill oil per day?
The key figure to remember is not the amount of oil but the EPA and DHA content: aim for at least 250 mg a day to meet the threshold associated with claims regarding heart and brain health.
In practical terms, this equates to one to three capsules, depending on the product’s concentration, which varies significantly from one brand to another. This is precisely why comparing ‘mg of oil’ figures between two product labels is of no informative value.
Is krill oil suitable for people with a fish allergy?
Be careful not to confuse two distinct allergies. Krill is a crustacean, not a fish. A person who is allergic to fish but not to crustaceans can therefore, in principle, tolerate krill oil, and the reverse is also true.
Given the potential severity of reactions to crustaceans, this matter should be discussed with an allergist rather than decided by deduction. For people allergic to both groups, oils derived from microalgae offer an alternative that does not come from marine animals.
Is krill a sustainable source?
This is a legitimate question, as krill is a keystone species in the Antarctic ecosystem on which whales, seals and penguins depend. Fishing there is regulated by an international commission which sets quotas well below the estimated biomass.
In practice, look for a sustainable fishing certification on the packaging. This is the most concrete indicator you have to distinguish between a regulated supply chain and an opaque one.
Can krill oil be combined with coenzyme Q10?
Yes, and there is a logical basis for this combination. The two act in complementary ways: omega-3s influence the composition of cell membranes, whilst coenzyme Q10 supports mitochondrial energy production and provides antioxidant protection.
Both are also fat-soluble, which means they should be taken at the same time, with a meal containing fat. Our article on coenzyme Q10 deficiency details the situations in which taking this supplement is beneficial.
If you need to bear three criteria in mind when making your choice, these are the ones, and they apply equally to krill oil and fish oil:
- The EPA and DHA content per daily dose, rather than the total amount of oil prominently displayed on the front of the bottle.
- The presence of an antioxidant – naturally included in krill oil in the form of astaxanthin – which should be checked in the ingredients list for fish oil.
- A traceable origin and certification, which, for this type of product, are the only reliable indicators of what you are actually buying.
