Trans-Resveratrol vs Resveratrol: What's the Difference?
on October 26, 2026

Trans-Resveratrol vs Resveratrol: What's the Difference?

Pick up two resveratrol supplements and you may see "resveratrol" on one label and "trans-resveratrol" on the other. They sound interchangeable, but the five letters at the front tell you which shape of the molecule you are actually getting.

Here is what the difference is, why it matters, and what to look for on a label.

What resveratrol is

Resveratrol is a polyphenol belonging to a small family of plant compounds called stilbenes. Plants make it as a defence response when they are damaged, stressed or attacked by fungi, which is why it concentrates in tough outer tissues like grape skins and roots.

It turns up in red grapes, berries, peanuts and cocoa, but always in small amounts. The richest natural source by far is the root of Japanese knotweed, which is where most supplement-grade resveratrol comes from.

Trans vs cis: two shapes of the same molecule

Resveratrol is two ring-shaped groups joined by a double carbon bond. That bond is rigid, so the rings can sit in one of two fixed arrangements:

  • Trans-resveratrol: the two rings sit on opposite sides of the bond, giving a long, flat, stretched-out shape.
  • Cis-resveratrol: the two rings sit on the same side, giving a bent, folded shape.

Same atoms, same formula, different geometry. Chemists call these isomers.

In nature, plants make the trans form. Stilbenes overwhelmingly occur as trans isomers because that shape is the more stable one. The cis form mostly appears when trans-resveratrol is exposed to light after it has been extracted, and some researchers report finding no cis-resveratrol in natural sources at all.

Why the difference matters

It is the form that is studied. Trans is the shape plants make and the form most resveratrol research has focused on. If you want what has been studied, trans is what you want.

It is the form that is authorised. In the EU, resveratrol in supplements is regulated as a novel food under the name "trans-resveratrol". The authorisation requires that exact designation on the label, sets a maximum of 150 mg per day, and requires a statement that people taking medicines should only use it under medical supervision.

It is sensitive to light. Trans-resveratrol readily converts to cis under UV light, and in solution it converts easily in ordinary daylight too. Protected from light, it is stable across a wide range of temperatures. So how a product is made, packed and stored decides how much of the trans form is still there when you take it.

How to read a resveratrol label

  1. Look for the word "trans". "Trans-resveratrol" tells you which form you are getting. Plain "resveratrol" leaves it open.
  2. Check milligrams of trans-resveratrol, not milligrams of extract. "500 mg Japanese knotweed extract (50% resveratrol)" is 250 mg of resveratrol, not 500. Look for the amount of trans-resveratrol per daily serving.
  3. Check the source. Most supplement resveratrol comes from Japanese knotweed root or is made synthetically. Either way, the label should say.
  4. Look for testing. Knotweed extracts can carry unwanted compounds, notably emodin, and plant extracts can pick up PAHs during processing. A good producer tests for both.
  5. Look at the packaging. Because trans-resveratrol is light-sensitive, packaging that keeps light out matters.

How we do it at IDUN. IDUN Liposomal Resveratrol contains 100 mg of trans-resveratrol per serving, from Japanese knotweed root. It is made in Germany by PlantaCorp and tested for PAH and emodin. We list trans-resveratrol by name and by milligram so you know exactly what is in each serving.

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