rTG Omega-3: Triple Strength, Higher Bioavailability

Omega-3 supplements come in four main chemical forms, and the form determines both how concentrated the oil can be and how the fatty acids are handled after being swallowed. rTG (re-esterified triglyceride) omega-3 has been reported in absorption studies to be absorbed more efficiently than the ethyl ester form.

The four forms

• Natural triglyceride (nTG). The form in whole fish and minimally processed fish oil: three fatty acids bound to a glycerol backbone, typically around 30 percent EPA plus DHA.
• Ethyl ester (EE). The fatty acids are cleaved from glycerol and bound to ethanol instead, which allows separation by molecular distillation to produce high-EPA or high-DHA concentrates.
• Re-esterified triglyceride (rTG). A further enzymatic step reattaches the concentrated fatty acids to glycerol, restoring a triglyceride structure while keeping the high EPA and DHA percentage.
• Phospholipid (PL). The form in krill oil, where omega-3 fatty acids are bound into phospholipids.

Why the triglyceride structure matters

Dietary fat digestion is built around triglycerides: pancreatic lipase releases their fatty acids for absorption in the small intestine. Ethyl esters are hydrolyzed more slowly and need a further step before entering the same pathway — a difference in digestive chemistry, which is what absorption studies measure.

What one crossover trial measured

In a randomized, open-label, crossover trial, participants took four omega-3 products — an rTG fish oil, an ethyl ester concentrate, krill oil (phospholipid), and salmon oil (natural triglyceride) — each for 28 days, separated by four-week washouts.

• The rTG fish oil produced the largest measured increase in blood EPA plus DHA.
• The reported rank order of measured increase was rTG, then ethyl ester, then krill oil, then salmon oil.

Products were dosed at each manufacturer's recommended serving, so the EPA and DHA delivered was not identical across arms; the finding describes measured blood levels, not a health outcome.

Concentration and reading a label

Concentration describes how much EPA plus DHA sits in a gram of oil. An oil at 60 to 85 percent carries about three times the omega-3 of a standard 30 percent oil in the same volume — the meaning of triple-strength labeling — so fewer or smaller capsules deliver the same amount. Look for milligrams of EPA and DHA per serving rather than total fish oil weight, since the two can differ threefold. Also note the stated form (nTG, EE, rTG, or PL), the species, and any freshness specification such as a TOTOX limit. Concentrated oils oxidize more readily and should be kept away from heat and light.

EPA contributes to maintaining normal heart function, and DHA is a structural fatty acid of the brain and retina that contributes to maintaining normal brain function and normal vision. Both come primarily from oily fish, so choosing a supplement means matching the EPA and DHA amount to your diet and confirming purity and freshness are documented.