OPC / Pine bark extract (Pycnogenol)

What it is

Proanthocyanidins are chains of catechin building blocks, a widespread group of plant polyphenols. The short chains are called oligomeric, hence the name OPC. They are found in high concentrations in grape seeds and in the bark of pine trees.

Commercially, there are two main sources. Grape seed extract is usually adjusted to a high OPC content; the EU Novel Food Catalogue lists extracts with 65 % to 95 % OPC. Pine bark extract usually comes from the maritime pine, Pinus pinaster. The branded extract Pycnogenol is standardized to 70 ± 5 % procyanidins and provides most of the studies. Other pine species such as Pinus radiata are also used. Important for the assessment: results apply in the first instance to the extract that was studied.

How it is supposed to work

OPC are considered antioxidants and are said to protect the blood vessels. Something has in fact been measured in humans. In a double-blind crossover study with 23 patients with coronary heart disease, 200 mg of Pycnogenol per day over 8 weeks improved flow-mediated dilation from 5.3 to 7.0, while nothing changed under placebo. At the same time, a marker of oxidative stress fell. The researchers explain the effect through the lower oxidative stress; blood pressure and inflammatory markers did not change.

A second route concerns the platelets. In smokers, 100 to 125 mg of Pycnogenol prevented smoking-induced platelet clumping similarly to 500 mg of aspirin, without prolonging bleeding time. In addition, anti-inflammatory effects and a strengthening of the vein walls are discussed, which come mainly from laboratory and animal studies.

What users are looking for

Many take OPC for the blood vessels, against heavy and swollen legs or on long flights. Others use pine bark extract for skin and joints, in a longevity stack as an antioxidant or together with L-arginine for potency. Parents of children with ADHD ask about it as a gentler supplement. People often report lighter legs and better circulation. These are user reports without a control group, some of which match the study signals.

What the studies show

The 2020 Cochrane review

The Cochrane authors pooled 27 randomized trials with 1,641 participants, spread across 10 conditions from asthma to diabetes to osteoarthritis. The studies lasted 4 weeks to 6 months. Per condition there were usually only one to three studies, and in 22 studies the risk of bias was unclear. For every endpoint, the authors rated the trustworthiness as very low and saw no basis for definitive conclusions, neither on efficacy nor on safety.

The ADHD study versus methylphenidate

88 children with ADHD, on average 10.1 years old, received placebo, Pycnogenol or the standard medication methylphenidate for 10 weeks. Pycnogenol was dosed at 20 or 40 mg per day depending on body weight. Teachers rated the total score and hyperactivity better under Pycnogenol and methylphenidate than under placebo; only the medication also improved inattention. 144 children were planned; the study ended early because of the pandemic.

The blood pressure question

Here the analyses contradict each other. A meta-analysis that admitted only double-blind, placebo-controlled trials found no effect on blood pressure across 7 studies with 626 participants. Other analyses with 12 and 27 studies found reductions between 1.91 and 3.22 mmHg. For grape seed extract, 300 mg per day did not significantly lower blood pressure in a well-conducted study with 70 participants.

Where the data stop

The biggest limitation is the size of the studies. Many have only a few dozen participants, run for a few weeks and measure surrogate markers such as vessel diameter or blood pressure. Hard endpoints such as heart attacks, strokes or mortality have not been studied. That the blood pressure meta-analyses reach opposite results depending on which studies are selected shows how sensitive the findings are. In 2021, EFSA saw no evidence for an effect of a grape seed extract on blood pressure.

In the vein and microcirculation studies, it is striking that a large proportion comes from a single Italian research group and is often designed as a registry or comparative study without placebo. This does not rule out an effect, but makes it harder to assess. For ADHD there are two small positive studies, one of which was ended early; independent confirmation on a larger scale is lacking. And finally, the results cannot be transferred at will: Pycnogenol is standardized, while other pine bark and grape seed products differ in composition and content.

Status, approval and legal

Pine bark and grape seed extracts are legally sold as food supplements in Germany and the EU. The European Commission’s Novel Food Catalogue lists maritime pine bark and grape seed extract with 65 % to 95 % OPC as not novel in food supplements. They therefore do not need their own authorization there, nor does Pycnogenol, which may thus be sold without a special novel food authorization. Health claims for OPC alone are not authorized; several applications on cholesterol, veins, vision, blood pressure and antioxidant effects were rejected. The only authorized claim concerns LDL lowering for a specific combination of 8 ingredients that contains, alongside 20 mg of maritime pine bark extract, red yeast rice among other things. I found no official maximum amounts from EFSA, BfR or DGE. OPC and pine bark extract are not on the WADA Prohibited List 2026.

Safety

OPC extracts are considered well tolerated. The US liver database LiverTox classifies pine bark extract as an unlikely cause of liver injury and lists gastrointestinal complaints, dizziness, headache and nausea as side effects. In 2025, a single case of severe muscle damage was described in a man who had taken more than the recommended amount. Because Pycnogenol inhibits platelets, caution is advisable when anticoagulants are taken at the same time; there are no dedicated interaction studies on this. Reliable data are lacking for pregnancy and breastfeeding. In children with ADHD, any supplement belongs under medical supervision; it does not replace an existing therapy. The Cochrane review notes that many studies did not report serious side effects at all.

Sources

• Robertson NU et al., Cochrane Database Syst Rev 2020 – pine bark extract for chronic disorders
• Mohammadi S et al., BMC Complement Med Ther 2025 – pine bark extract and cardiometabolic risk factors
• Fogacci F et al., Angiology 2020 – Pycnogenol and blood pressure, meta-analysis
• Enseleit F et al., Eur Heart J 2012 – Pycnogenol and endothelial function in coronary heart disease
• Weyns AS et al., J Funct Foods 2022 – pine bark extract in ADHD versus methylphenidate
• Martinez-Zapata MJ et al., Cochrane Database Syst Rev 2020 – venoactive drugs for venous insufficiency
• Zhang H et al., Medicine 2016 – grape seed extract and blood pressure, meta-analysis
• EFSA NDA Panel, EFSA J 2021 – grape seed extract and blood pressure
• LiverTox (NIH) – Pine Bark
• Pütter M et al., Thromb Res 1999 – Pycnogenol and platelet aggregation