Trans-Resveratrol vs. Resveratrol: Reading the Label
The Dose AnalysisTrans-resveratrol vs. resveratrol comes down to chemistry: trans-resveratrol is one of the two shapes (isomers) the resveratrol molecule can take, and "resveratrol" on a label can mean either shape or simply the weight of a plant extract. To read the label, look for the word "trans," the percent it is standardized to, and whether the amount shown is the pure compound or the extract. A label number is not a blood level, and it is not an outcome.
Key takeaways
- Resveratrol exists as a trans form and a cis form, and an extract "standardized to 50% trans-resveratrol" holds about half its weight as trans-resveratrol.
- In a 2004 study of six volunteers, at least 70% of a 25 mg oral dose of pure, lab-made resveratrol (not a knotweed extract) was absorbed, but only trace amounts reached the blood unchanged; a blood level is a marker, not a health result.
- Memorial Sloan Kettering Cancer Center advises talking with your healthcare provider if you take blood thinners such as warfarin, because resveratrol may increase the risk of bleeding.
What "trans" and "cis" mean
Resveratrol is a plant compound found in grape skins and seeds, peanuts, pistachios, some berries and Japanese knotweed (Polygonum cuspidatum), according to Memorial Sloan Kettering Cancer Center's About Herbs database. The molecule can take two shapes. In the trans shape the two ring groups sit on opposite sides of a double bond; in the cis shape they sit on the same side.
The two shapes are not interchangeable in the lab. A 2019 study from Sapienza University of Rome, published in the Journal of Agricultural and Food Chemistry, notes that on UV-light exposure resveratrol can change from the trans form to the cis form. A 2020 study in Nutrients describes trans-resveratrol as the form that has been studied intensively, and in a cell model of the gut lining it found that most trans-resveratrol passed through unchanged while most cis-resveratrol was broken down. That was a cell model, not a study in people.
How to read a resveratrol label
A resveratrol label can describe the same capsule in very different ways. One question to ask is whether a number is the weight of the compound or the weight of the plant extract that contains it.
The percent-to-milligram math
When a label says an extract is "standardized to" a percent of trans-resveratrol, multiply the extract weight by that percent. For example, 500 mg of an extract standardized to 50% trans-resveratrol holds about 250 mg of trans-resveratrol (500 x 0.50). The same 500 mg standardized to 10% holds about 50 mg. Standardization tells you how much of a marker compound the extract was made to contain. It does not by itself tell you how well the compound is absorbed or what it does.
| What the label line says | What it tells you | What it does not tell you |
|---|---|---|
| Trans-resveratrol 250 mg | The weight of the trans form per serving | The plant source, unless the label names it |
| Resveratrol 250 mg | A weight of resveratrol per serving | Which isomer, unless the label says "trans" elsewhere |
| Japanese knotweed root extract 500 mg (50% trans-resveratrol) | The extract weight and its trans-resveratrol percent | The trans amount itself; multiply to get about 250 mg |
| Resveratrol blend 600 mg with two extracts at different percents | The blend total and the strength of each extract | How the 600 mg is split between the extracts |
Blend totals are on the label; the amounts inside each blend are not.
An example: Resveratrol+
Resveratrol+, the CuraMyHealth product reviewed on this site, lists one capsule per serving with a 600 mg Resveratrol Blend of Japanese Knotweed (10% Trans-Resveratrol) (Polygonum cuspidatum) root and Japanese Knotweed (50% Trans-Resveratrol) (Polygonum cuspidatum) root. Its product page says the 600 mg should be read as the blend weight rather than pure trans-resveratrol. The source is knotweed root, not grapes or wine.
The label's suggested use is to take one (1) capsule daily, preferably 20-30 minutes before a meal, or as directed by your healthcare professional. Its caution reads: "Do not exceed recommended dose. Pregnant or nursing mothers, children under the age of 18, and individuals with a known medical condition should consult a physician before using this or any dietary supplement." The label also says to keep it out of reach of children, not to use it if the safety seal is damaged or missing, and to store it in a cool, dry place.
Absorbed is not the same as available
Another gap between a label and the body is what happens after you swallow. In a 2004 study in Drug Metabolism and Disposition, six volunteers took a 25 mg oral dose of radio-labelled resveratrol. At least 70% was absorbed, yet only trace amounts of unchanged resveratrol (under 5 ng/mL) showed up in the blood. Most of the dose was recovered in urine, as sulfate and glucuronide forms and a form likely made by gut bacteria; the authors said very fast sulfate conversion by the gut and liver appears to be what limits how much reaches the blood. They also noted that these breakdown products may still be active. That study used a pure lab form of resveratrol, not a knotweed extract.
A 2011 review in the Annals of the New York Academy of Sciences by the same lead author put oral absorption at about 75% and oral bioavailability (the share that reaches the blood unchanged) at considerably less than 1%. The review found that taking larger or repeated doses did not appear to change this much.
Two points follow for a reader. First, a blood level is a marker of what the body did with a dose, not proof of a health effect. Second, the doses in these studies were set by the researchers. A study dose is not a label direction, and a label that does not list a trans-resveratrol amount cannot be matched to a study dose milligram for milligram.
Safety notes before you start
Memorial Sloan Kettering Cancer Center advises talking with your healthcare provider before taking resveratrol supplements, because of its estrogen-like properties and possible drug interactions. It also advises talking with your healthcare provider if you take blood thinners such as warfarin, because resveratrol may increase the risk of bleeding, and it notes that use with antiplatelet drugs may raise bleeding risk, although the clinical relevance is not yet known. It reports that 1 gram a day for 4 weeks changed several drug-processing (CYP450) enzymes (CYP3A4, 2D6, 2C9 and 1A2) in healthy volunteers, which can affect the levels of medicines broken down by those enzymes. In an animal study, Polygonum cuspidatum raised blood levels of the seizure medicine carbamazepine; the clinical relevance is not yet known.
The same source says people with hormone-sensitive cancers should use caution because resveratrol has estrogen-like properties, and that high doses of 2.5 and 5 g a day caused mild to moderate stomach upset and diarrhea. The human studies behind the 1 gram enzyme finding and the 2.5 g and 5 g stomach-upset finding used pure resveratrol, not a knotweed root extract, and all three amounts are more than the 600 mg blend in one Resveratrol+ capsule. If you are pregnant, nursing or trying to conceive, ask your healthcare provider before use.
Frequently asked questions about trans-resveratrol and resveratrol
Is trans-resveratrol better than resveratrol?
Trans-resveratrol is one form of resveratrol, not a separate ingredient. A 2020 Nutrients paper describes trans-resveratrol as the form that has been studied intensively. Whether one product works better than another is not shown by the isomer name alone.
What does "standardized to 50% trans-resveratrol" mean?
It means about half the extract's weight is trans-resveratrol. Multiply the extract weight by 0.50 to estimate the trans-resveratrol amount; 500 mg of such an extract holds about 250 mg.
Does resveratrol absorb well?
Absorption and availability differ. In a 2004 study of six volunteers, at least 70% of a 25 mg oral dose of pure, lab-made resveratrol (not a knotweed extract) was absorbed, but only trace amounts reached the blood unchanged; the authors said very fast conversion by the gut and liver appears to be the main reason, according to Drug Metabolism and Disposition.
Can I take resveratrol with blood thinners?
Memorial Sloan Kettering Cancer Center advises talking with your healthcare provider if you take blood thinners such as warfarin, because resveratrol may increase the risk of bleeding. The same advice applies to antiplatelet medicines.
Why does light matter for resveratrol?
A 2019 study in the Journal of Agricultural and Food Chemistry notes that UV-light exposure can change resveratrol from the trans form to the cis form. That is one reason the isomer named on a label matters.
Related reading
- Resveratrol+ review
- Turmeric vs. Curcumin: What Changes in a Supplement?
- Optional next step: our supplement audit can help you organize your goals; it does not diagnose anything.
Sources
- Memorial Sloan Kettering Cancer Center: About Herbs - Resveratrol, updated 2023.
- Drug Metabolism and Disposition (Walle T, et al.): High absorption but very low bioavailability of oral resveratrol in humans, 2004.
- Annals of the New York Academy of Sciences (Walle T): Bioavailability of resveratrol, 2011.
- Nutrients (Jarosova V, et al.): Metabolism of cis- and trans-Resveratrol and Dihydroresveratrol in an Intestinal Epithelial Model, 2020.
- Journal of Agricultural and Food Chemistry (Francioso A, et al.): Gas Chromatographic-Mass Spectrometric Method for the Simultaneous Determination of Resveratrol Isomers and 2,4,6-Trihydroxyphenanthrene in Red Wines Exposed to UV-Light, 2019.
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This article is for education and is not personal medical advice. A qualified healthcare professional can help assess your needs and review the specific formula. Individual results vary.
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