Krill Oil vs Fish Oil: Bioavailability, Phospholipids and What Research Shows

Krill oil and fish oil are both marine sources of the long-chain omega-3 fatty acids EPA and DHA. The main difference is not that one contains omega-3 and the other does not—it is how those fatty acids are packaged within the oil.

In krill oil, a substantial portion of EPA and DHA can be associated with phospholipids. Fish-oil supplements, depending on the product, may provide EPA and DHA primarily as triglycerides, re-esterified triglycerides, ethyl esters, or other formulated lipid structures.

These differences can influence digestion, absorption, and the way EPA and DHA appear in blood after supplementation. But they do not support a universal claim that krill oil is always a fixed percentage more bioavailable than fish oil.

“Krill oil and fish oil cannot be compared accurately by ingredient name alone. EPA+DHA dose, chemical form, formulation, meal conditions, study duration, and the biomarker being measured all matter.”

Krill Oil vs Fish Oil at a Glance

What Are EPA and DHA?

EPA, or eicosapentaenoic acid, and DHA, or docosahexaenoic acid, are long-chain omega-3 fatty acids found in marine foods and marine oils.

Both krill oil and fish oil can provide EPA and DHA.

This means that when comparing two supplements, the number on the front of the bottle can be misleading.

For example:

• 1,000 mg of fish oil does not necessarily mean 1,000 mg of EPA+DHA
• 500 mg of krill oil does not necessarily mean 500 mg of EPA+DHA
• Two products with the same total oil weight can provide very different amounts of omega-3 fatty acids

The useful comparison is the amount of actual EPA and DHA—or clearly disclosed total omega-3 containing EPA and DHA—per serving.

How Are Omega-3s Structured in Krill Oil?

A notable feature of krill oil is its phospholipid content.

Phospholipids are amphiphilic molecules, meaning they contain regions that interact with water and regions that interact with fats.

They are major structural components of biological membranes.

In krill oil, a portion of EPA and DHA can be incorporated into phospholipid molecules.

This differs from many conventional fish oils, where omega-3 fatty acids may be carried primarily in triglyceride or ethyl-ester structures.

However, descriptions such as “phospholipid-bound omega-3 goes directly into your cells” oversimplify human digestion and lipid metabolism.

Krill oil still undergoes digestion, enzymatic processing, intestinal absorption, transport, metabolism, and tissue incorporation.

Are All Fish Oils Triglycerides?

No.

One of the biggest problems with simple “krill oil vs fish oil” comparisons is treating all fish oils as chemically identical.

Fish-oil supplements may contain omega-3 fatty acids in several forms.

• Natural triglycerides: Fatty acids attached to a glycerol backbone in the form naturally found in many marine oils.
• Re-esterified triglycerides (rTG): Concentrated omega-3s converted back into a triglyceride structure after processing.
• Ethyl esters (EE): Concentrated fatty acids chemically linked to ethanol rather than glycerol.
• Emulsified or other delivery systems: Formulations designed to alter dispersion and digestion.

Different forms can behave differently, particularly depending on whether they are consumed with food and how much dietary fat is present.

For that reason, a study comparing krill oil with one ethyl-ester fish oil does not establish how krill oil compares with every triglyceride, re-esterified triglyceride, or emulsified fish-oil product.

What Does “Bioavailability” Actually Mean?

“Bioavailability” is often used as if it were one simple number, but omega-3 studies measure several different outcomes.

Researchers may assess:

• Cmax: The highest measured blood concentration after a dose
• Tmax: How long it takes to reach that peak
• AUC: Total exposure across a defined period of time
• Plasma EPA and DHA: Changes in circulating fatty acids
• Plasma phospholipid EPA and DHA: EPA/DHA incorporated into that lipid fraction
• Red-blood-cell EPA and DHA: A longer-term incorporation measure
• Omega-3 Index: EPA plus DHA as a percentage of total fatty acids in red-blood-cell membranes

These measures answer related but different questions.

What Did Early Krill Oil vs Fish Oil Studies Find?

Several frequently cited human studies have produced favorable results for particular krill-oil preparations—but they did not all measure the same thing.

Equal-Dose Single-Dose Study

One randomized crossover study in 12 healthy men compared approximately 1,680 mg of EPA+DHA supplied as krill oil, fish-oil re-esterified triglycerides, or fish-oil ethyl esters.

EPA+DHA incorporation into plasma phospholipids over 72 hours was highest after the krill-oil preparation, followed by re-esterified triglycerides and ethyl esters.

This supports the possibility that formulation can influence acute EPA/DHA handling.

It does not establish a fixed percentage advantage that applies to every krill-oil and fish-oil product.

Four-Week Omega-3 Index Study

Another randomized crossover trial involved 24 healthy adults.

Participants received krill oil or fish oil providing the same 600 mg daily amount of n-3 polyunsaturated fatty acids for four weeks.

The krill-oil phase produced larger increases in plasma and red-blood-cell omega-3 measurements, including the Omega-3 Index, compared with the fish-oil phase.

However, this was a small study using specific formulations.

Single-Dose Study With Approximately 1,700 mg EPA+DHA

A later randomized crossover study compared krill oil, krill meal, and fish oil in 15 healthy participants, with each treatment providing approximately 1,700 mg of EPA+DHA.

The 72-hour incremental area under the curve for EPA and DHA in plasma phospholipids was higher after krill oil than after fish oil.

Importantly, however, the researchers found no significant difference between krill meal and fish oil.

They specifically noted that this finding argued against the overly simple explanation that phospholipids are inherently always better absorbed than triglycerides.

Have Studies Ever Found Similar Bioavailability?

Yes.

A randomized four-week study involving 66 healthy adults compared equal daily doses of approximately 1.3 grams of EPA+DHA delivered as:

• Fish-oil ethyl esters
• Fish-oil triglycerides
• Krill oil

At the study's primary four-week plasma EPA+DHA endpoint, the differences between groups were not statistically significant.

The measured bioavailability differences between the formulations were relatively modest.

This is an important counterexample to claims that krill oil universally produces dramatically greater absorption than fish oil.

What Does the Newer Research Show?

More recent evidence continues to suggest that formulation matters, while also showing why universal superiority claims are difficult to justify.

2024 Network Meta-Analysis

A 2024 network meta-analysis evaluated 26 studies comparing different omega-3 sources, molecular forms, and doses.

The analysis generally favored lower-dose krill oil for several bioavailability measures.

But the results also showed that:

• Fish-oil formulation significantly influenced performance
• Emulsified fish oil performed strongly for peak concentration measurements
• Different ethyl-ester doses affected time-to-peak measurements differently
• Different formulations ranked differently depending on the pharmacokinetic endpoint
• Some comparisons had limited statistical certainty
• Heterogeneity across the studies was high

The useful conclusion is therefore not simply “krill wins.”

It is that molecular form, dose, formulation, and measurement method substantially affect omega-3 bioavailability.

Recent 12-Week Randomized Trial

A more recent double-blind randomized trial included 72 healthy adults who received approximately 1.1 grams per day of omega-3 fatty acids from either krill oil or fish oil for 12 weeks.

The krill-oil group showed greater increases from baseline in plasma EPA and DHA than the fish-oil group.

That adds useful evidence that certain krill-oil formulations can produce higher circulating EPA and DHA under matched omega-3 conditions.

It still does not establish that every krill-oil supplement has the same advantage over every fish-oil formulation.

Is Krill Oil Really “48% More Bioavailable”?

That number should not be used as a universal property of krill oil.

A percentage difference in a clinical study is calculated from:

• A specific krill-oil product
• A specific comparison fish oil
• A specific EPA+DHA dose
• A particular population
• A particular biological measurement
• A defined period of time

Changing any of those factors can change the result.

It is therefore inappropriate to write:

• “Krill oil is 48% better absorbed than fish oil”
• “Krill oil has 48% higher bioavailability”
• “Phospholipids make all krill oil 48% more effective”
• “A lower dose of krill produces the same clinical result as a higher dose of fish oil”

unless the statement precisely describes the specific study and outcome being cited.

Do Phospholipids Make Krill Oil Better?

Phospholipids are one scientifically interesting difference between krill oil and many conventional fish oils.

They may influence digestion, transport, and incorporation of EPA and DHA.

But they should not be treated as a guarantee of superior clinical performance.

Several additional variables matter:

• The percentage of omega-3 carried in phospholipid form
• Total EPA and DHA dose
• Other lipid classes in the oil
• Processing and formulation
• Whether the supplement is taken with food
• The comparator fish-oil form
• The length of supplementation

The phospholipid content is therefore useful product information, not a shortcut to a guaranteed health result.

Can You Use Less Krill Oil Than Fish Oil?

This question is often framed incorrectly.

The total number of milligrams of oil is not the same as the amount of EPA and DHA.

A 500 mg krill-oil capsule could provide substantially less EPA+DHA than a 1,000 mg fish-oil capsule—or vice versa—depending on the formulations being compared.

The better comparison is:

How much EPA and DHA does each daily serving actually provide?

Bioavailability may influence how a particular formulation changes blood omega-3 levels, but it does not justify assuming that any lower-dose krill-oil product is clinically equivalent to a higher-dose fish oil.

Does Krill Oil Cause Fewer “Fishy Burps”?

Some people report different gastrointestinal experiences with different marine-oil formulations, but krill oil cannot be guaranteed to eliminate reflux or an unpleasant aftertaste.

Omega-3 supplements can cause gastrointestinal effects such as:

• Unpleasant taste or aftertaste
• Heartburn
• Nausea
• Stomach discomfort
• Diarrhea

Claims that phospholipids make krill oil “water-soluble” and therefore eliminate fishy burps oversimplify lipid chemistry and human digestion.

Is Krill Oil More Stable Because It Contains Astaxanthin?

Krill naturally contains astaxanthin, the carotenoid responsible for much of its reddish color.

Astaxanthin has antioxidant activity and may contribute to oxidative stability within a particular oil matrix.

However, the stability of an omega-3 supplement also depends on:

• Raw-material quality
• Processing
• Oxygen exposure
• Temperature
• Light exposure
• Packaging
• Added antioxidants
• Storage time

The presence of astaxanthin does not prove that a krill-oil product cannot oxidize, nor that conventional fish oil is inherently rancid or unstable.

Which Is Better: Krill Oil or Fish Oil?

For most people, there is no evidence-based answer that makes one source universally better.

Instead, compare products using several practical criteria:

• EPA+DHA amount: How much long-chain omega-3 does the daily serving actually provide?
• Form: Is it krill phospholipid-rich oil, fish-oil triglyceride, re-esterified triglyceride, ethyl ester, or another formulation?
• Serving size: How many capsules are required?
• Tolerability: Does the product cause digestive discomfort for you?
• Allergens: Is krill, fish, or another marine source relevant to an allergy?
• Other ingredients: Does the formula contain other compounds that change how the product should be evaluated?
• Reason for use: Are you simply supplementing dietary omega-3, or managing a medical condition that requires professional guidance?

If the goal is to treat very high triglycerides or another diagnosed condition, an over-the-counter supplement comparison should not replace clinical evaluation or prescribed therapy.

What About Shellfish and Fish Allergies?

Krill are crustaceans, while fish oil is derived from fish.

People with a known crustacean shellfish allergy should be cautious with krill products and review the product’s allergen information.

People with a known fish allergy should likewise discuss fish-derived supplements with an appropriate healthcare professional.

Do not assume that purification automatically eliminates allergy risk.

What Does RevitaPlus Beauty Pack Provide?

RevitaPlus Beauty Pack contains an Antarctic krill-oil softgel as one of six daily supplement components.

The current public Supplement Facts information lists:

• Antarctic Krill Oil — 500 mg
• Total Omega-3s (EPA/DHA) — 200 mg
• Phospholipids — 200 mg
• Astaxanthin — 150 mcg

For a broader review of krill oil itself—including EPA, DHA, astaxanthin, health research, and safety—read our guide to what krill oil is and what human research actually shows.

The Key Takeaway

Krill oil and fish oil are both sources of EPA and DHA, but their lipid structures and formulations can differ.

Several human studies have reported favorable absorption or incorporation measures with particular krill-oil preparations, including changes in plasma EPA/DHA, red-blood-cell fatty acids, or the Omega-3 Index.

Other studies have reported smaller or nonsignificant differences, and newer analyses show that fish-oil formulation can strongly affect bioavailability as well.

The research therefore does not support a universal rule that:

• Krill oil is always 48% more bioavailable
• Phospholipid omega-3 bypasses digestion
• Krill oil enters cells directly
• All fish oil is poorly absorbed
• A smaller krill-oil dose automatically equals a larger fish-oil dose
• Higher bioavailability guarantees better clinical outcomes

A responsible comparison starts with the actual EPA+DHA dose, lipid form, formulation, study design, and endpoint measured.

That provides a much more accurate answer than asking whether every krill oil is simply “better” than every fish oil.

This article is for general educational purposes and is not a substitute for medical advice, diagnosis, or treatment.