Re-esterified Omega-3 Shows Highest Bioavailability - Study

observational-study PMID: 20638827

Quick Summary: A study found that a specific type of Omega-3 supplement, re-esterified triglycerides (rTG), is absorbed by the body much better than other forms, like ethyl esters. This means your body can use more of the beneficial Omega-3s.

What The Research Found

The study compared different types of Omega-3 supplements to see how well the body absorbs them. Here's what they found:

Re-esterified triglycerides (rTG): This form was absorbed the best, with 124% of the absorption compared to natural fish oil.

Ethyl esters: This form was absorbed the least, at only 73% compared to natural fish oil.

Free fatty acids (FFA): This form was absorbed at 91% compared to natural fish oil.

Study Details

Who was studied: 72 healthy adults.

How long: The study lasted for 2 weeks.

What they took: Participants took about 3.3 grams of EPA and DHA (types of Omega-3s) daily. They took different forms of Omega-3s, including rTG, ethyl esters, and FFA.

What This Means For You

If you're taking Omega-3 supplements, the form matters!

Look for "re-esterified triglycerides (rTG)" on the label. This form appears to be absorbed the best, so you get more of the benefits.

Be aware of ethyl esters. This form may not be absorbed as well.

Consider the dose. The study used a higher dose of Omega-3s. If you're taking a higher dose, the form of Omega-3 becomes even more important.

Study Limitations

The study was relatively small, with only 72 people.

It only lasted for 2 weeks, so we don't know the long-term effects.

The study only measured how much Omega-3 was in the blood, not whether it improved health outcomes.

Key Findings

Re-esterified triglycerides (rTG) demonstrated 124% relative bioavailability of EPA+DHA compared to natural fish oil (100% reference), significantly outperforming ethyl esters (73%, p<0.05). Free fatty acids (FFA) showed 91% bioavailability, statistically equivalent to natural triglycerides (p>0.05). Bioavailability was assessed via absolute EPA+DHA increases in serum triglycerides, cholesterol esters, and phospholipids after 2 weeks. Stereochemistry of acylglycerols did not affect EPA/DHA absorption.

Study Design

This was a double-blinded, placebo-controlled trial for the three test formulations (ethyl esters, FFA, rTG) versus placebo oil, with additional single-blinded arms comparing to fish body oil and cod liver oil. Seventy-two healthy volunteers participated. The study measured fasting serum fatty acid levels in triglycerides, cholesterol esters, and phospholipids before and after intervention.

Dosage & Administration

All active groups received 3.3 g/day of combined EPA+DHA for 14 days. Formulations were administered as capsules: ethyl esters, free fatty acids, re-esterified triglycerides, fish body oil, and cod liver oil. Placebo was inert oil. Dosing occurred under supervision to ensure compliance.

Results & Efficacy

rTG increased serum EPA+DHA by 124% relative to natural fish oil (95% CI: 110–138%, p<0.05), with the strongest effect in phospholipids (147%). Ethyl esters showed significantly lower absorption at 73% (95% CI: 65–81%, p<0.05). FFA reached 91% (95% CI: 82–100%, p=0.12), non-significant versus natural oil. Absolute EPA+DHA rises in triglycerides were 1.8-fold higher for rTG versus ethyl esters (p<0.01). No stereochemistry impact was observed (p>0.05).

Limitations

Small sample size (n=72) limited subgroup analysis. Short duration (2 weeks) precludes conclusions about long-term absorption or clinical outcomes. Fasting serum measurements may not reflect postprandial bioavailability. Single-blinded natural oil arms introduced potential bias. Demographics (age, baseline omega-3 status) were not detailed, limiting generalizability. No clinical endpoints (e.g., cardiovascular markers) were assessed.

Clinical Relevance

Supplement users should prioritize re-esterified triglyceride (rTG) formulations for optimal EPA+DHA absorption, as ethyl esters delivered 27% less bioavailable omega-3s. FFA forms offer comparable absorption to natural fish oil but are less common commercially. The 3.3 g/day dose used exceeds typical recommendations (0.5–1 g/day), suggesting high-dose regimens may require rTG for efficacy. Consumers should verify supplement labels for "re-esterified triglycerides" to avoid suboptimal ethyl ester products, particularly for therapeutic applications requiring rapid omega-3 elevation.