What is the difference between triglyceride and ethyl ester omega-3?

In natural fish oil, EPA and DHA are attached to a glycerol backbone as triglycerides — the same molecular form found in whole fish. To concentrate EPA/DHA, manufacturers use ethanol transesterification, replacing the glycerol with ethanol to create ethyl esters. This form is cheaper to produce but absorbs approximately 27% less efficiently. Re-esterified triglyceride (rTG) products reconvert the ethyl esters back to a triglyceride structure, recovering the absorption advantage at a higher cost.

Is krill oil better than fish oil?

Krill oil and fish oil have different strengths. Krill oil carries omega-3s as phospholipids, which may preferentially cross the blood-brain barrier and are absorbed without requiring bile acids. Krill oil also contains choline and astaxanthin. However, krill oil provides significantly less EPA and DHA per capsule than concentrated fish oil products. For achieving higher omega-3 blood levels, a high-quality rTG fish oil typically offers better gram-for-gram efficiency.

Should omega-3 supplements be taken with food?

Yes. Omega-3 absorption is significantly higher when taken with a fat-containing meal. A meal with dietary fat stimulates bile acid release, which is required for effective absorption of triglyceride-form omega-3s. Studies show that taking fish oil in a fasted state can reduce EPA/DHA absorption by 50% or more compared to taking it with a meal — an effect particularly pronounced with ethyl ester forms.

Moderate Evidence

Best Form of Omega-3: A Clinical Guide

Fish oil supplements differ substantially in how they deliver EPA and DHA to the body. The molecular form — natural triglyceride, ethyl ester, or re-esterified triglyceride — determines how efficiently the omega-3 fatty acids are absorbed. Most budget fish oils use the ethyl ester form for cost reasons, but this form consistently underperforms triglyceride-based products in absorption studies.

Updated 2026 · Reviewed by Dr. Brennan Commerford, D.C.

Our Recommendation

Our Pick

Re-esterified Triglyceride (rTG)

The rTG form achieves approximately 124% relative bioavailability compared to natural fish oil (the 100% reference), outperforming ethyl ester concentrates (~73%) in head-to-head absorption studies. The triglyceride backbone mirrors the natural structure of EPA and DHA in food.

All Forms Compared

Best

Re-esterified Triglyceride (rTG)

Bioavailability

~124% relative to natural fish oil

Best For

Cardiovascular support, anti-inflammatory support

EPA/DHA re-attached to a glycerol backbone — mirrors the natural food form.

Best

Natural Triglyceride (NTG)

Bioavailability

100% (reference standard)

Best For

Moderate-concentration fish oil, food-first approach

The form found in whole fish. Lower EPA/DHA concentration per gram than concentrates.

Good

Krill Oil (Phospholipid Form)

Bioavailability

High — phospholipid carrier with preferential brain uptake

Best For

Brain support, smaller daily dose

Contains choline alongside omega-3s. Lower absolute EPA/DHA per capsule than fish oil concentrates.

Avoid

Ethyl Ester (EE)

Bioavailability

~73% relative to natural fish oil

Best For

N/A — most budget fish oil concentrates

Requires pancreatic esterase to cleave the ethyl group before absorption. Absorption is further reduced when taken in a fasted state.

Frequently Asked Questions

What is the difference between triglyceride and ethyl ester omega-3?: In natural fish oil, EPA and DHA are attached to a glycerol backbone as triglycerides — the same molecular form found in whole fish. To concentrate EPA/DHA, manufacturers use ethanol transesterification, replacing the glycerol with ethanol to create ethyl esters. This form is cheaper to produce but absorbs approximately 27% less efficiently. Re-esterified triglyceride (rTG) products reconvert the ethyl esters back to a triglyceride structure, recovering the absorption advantage at a higher cost.
Is krill oil better than fish oil?: Krill oil and fish oil have different strengths. Krill oil carries omega-3s as phospholipids, which may preferentially cross the blood-brain barrier and are absorbed without requiring bile acids. Krill oil also contains choline and astaxanthin. However, krill oil provides significantly less EPA and DHA per capsule than concentrated fish oil products. For achieving higher omega-3 blood levels, a high-quality rTG fish oil typically offers better gram-for-gram efficiency.
Should omega-3 supplements be taken with food?: Yes. Omega-3 absorption is significantly higher when taken with a fat-containing meal. A meal with dietary fat stimulates bile acid release, which is required for effective absorption of triglyceride-form omega-3s. Studies show that taking fish oil in a fasted state can reduce EPA/DHA absorption by 50% or more compared to taking it with a meal — an effect particularly pronounced with ethyl ester forms.

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FormulaForge formulates and sells supplements containing the ingredients discussed on this page. Our formulary recommendations are based on peer-reviewed bioavailability research. All cited studies are independently verifiable.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.