Also known as: Trans-resveratrol, Japanese knotweed extract, Polygonum cuspidatum, Grape polyphenol
FoundationalEmerging evidence
A polyphenol from grape skin and Japanese knotweed, once heralded as the explanation for the French paradox. Bioavailability is very poor, and human results have consistently failed to match the enthusiasm generated by cell and animal work.
Typical dose
150.0–500.0 mg per day
With a fat-containing meal; away from training sessions
What it is
Resveratrol is a stilbenoid polyphenol produced by plants in response to stress and pathogen attack. It occurs in grape skins, red wine, blueberries and peanuts, though the main commercial source is Japanese knotweed, which contains far higher concentrations.
Two isomers exist. Trans-resveratrol is the biologically relevant form; cis-resveratrol is not. Reputable products specify trans-resveratrol content, and a label saying only resveratrol without that specification is worth questioning.
Its reputation originated with the French paradox and with early work suggesting sirtuin activation and lifespan extension in simple organisms. Much of that early story has been complicated or contradicted by later research, and it is worth understanding this as a compound whose reputation ran considerably ahead of its evidence.
How it works
The most publicised mechanism is activation of SIRT1, a sirtuin enzyme involved in metabolic regulation and DNA repair. Later work suggested this activation may be indirect, possibly mediated through AMPK, and the original interpretation has been actively disputed in the literature.
Resveratrol also has direct antioxidant activity, influences nitric oxide production with implications for vascular function, and affects inflammatory signalling pathways including NF-kB.
The dominant practical problem is bioavailability. Resveratrol is absorbed reasonably well but metabolised so rapidly that free resveratrol in plasma is minimal. Whether its metabolites retain activity is an open question, and this gap between administered dose and available compound is the most likely explanation for disappointing human results.
What the evidence shows
Cell and animal research is voluminous and often impressive, covering metabolic health, cardiovascular markers, neuroprotection and lifespan in model organisms. Human results have been far less consistent.
Meta-analyses of human trials on glucose control, lipids and blood pressure have produced mixed findings, with some reporting small benefits in specific populations and others none. A notable and frequently cited trial found that resveratrol blunted some of the beneficial adaptations to exercise training in older men, which is close to the opposite of what a performance supplement should do.
The reasonable summary is that resveratrol is one of the clearest examples in this field of a compound where preclinical promise has not translated. That does not make it useless, but it does make confident claims unjustifiable.
Dosing
Common supplemental range is 150-500 mg daily of trans-resveratrol. Trials have used from 75 mg up to 5,000 mg, with higher doses reliably causing digestive upset.
Taking it with a fat-containing meal improves absorption. Some evidence suggests piperine co-ingestion slows metabolism and raises plasma levels, and combinations with quercetin are marketed on similar grounds.
One practical caution specific to this compound: if you are training for adaptation, the trial suggesting blunted exercise response is worth taking seriously enough to avoid taking it around training sessions.
At a glance
Common forms
Trans-resveratrol (Japanese knotweed), Grape extract resveratrol, Liposomal resveratrol, Combined with quercetin or piperine
Half-life / duration
Rapidly metabolised; free plasma resveratrol is short-lived
Timing
With a fat-containing meal; away from training sessions
Competition status
Permitted — not on the WADA Prohibited List
Category
Foundational
Safety and side effects
Well tolerated at typical supplemental doses. Higher intakes, generally above 1,000 mg daily, commonly cause nausea, diarrhoea and abdominal discomfort.
Resveratrol affects some of the enzyme systems the body uses to process medicines, and also influences how readily blood clots. Anyone taking regular medication should seek advice before use.
The exercise adaptation finding is worth repeating here, not because it is dangerous but because someone supplementing to improve training outcomes should know there is trial evidence pointing the other way.
Who should avoid it
Speak to your doctor before use if you take any regular medication — resveratrol affects how the body processes medicines and influences clotting. Seek advice if your hormones are being monitored or managed. Avoid in pregnancy and breastfeeding. Stop before scheduled surgery.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
