Pycnogenol: What the Pine Bark Trials Really Show

Pycnogenol is a branded extract of French maritime pine bark, and it may be one of the most studied supplement ingredients you have never heard of. Its maker, Horphag Research, and the brands that use it point to hundreds of published studies covering blood pressure, circulation, knee comfort, blood sugar, skin, menopause, attention in children and more. Few supplements can claim a research list that long.

Length is not the same as strength, though. When independent reviewers sorted through the trials, they found that most were small, that supplement makers funded most of them, that a large share came from one Italian research group whose studies were mostly open and unrandomized, and that the better-controlled trials usually showed smaller effects or none. This guide explains what Pycnogenol is, what each part of the evidence shows, how it differs from cheaper generic pine bark extract, what it costs and what to know about safety.

What Pycnogenol is

Pycnogenol is a water extract of the bark of the French maritime pine (Pinus pinaster), sold by Horphag Research. The US Pharmacopeia's monograph for maritime pine extract requires 65 to 75 percent procyanidins, which matches the "70 percent, plus or minus 5" figure on many labels. Procyanidins are chains of catechin-type polyphenols, related to the compounds in grape seed, cocoa and tea. The extract also contains catechin, taxifolin and phenolic acids such as caffeic and ferulic acid.

The large procyanidin chains themselves are poorly absorbed. In a small study that tracked what reaches the bloodstream, what showed up in the blood after a dose were small phenolic compounds and a metabolite called M1, which gut bacteria make from catechin and which peaked about 10 hours after a dose. Levels were low and varied a lot from person to person. Most proposed effects, such as more nitric oxide in blood vessel walls and lower oxidative stress, come from lab and animal work plus a handful of human biomarker studies.

"Pycnogenol" is a trademark, not a generic name. Horphag's license terms require a product to contain at least 20 mg a day of the extract to use the name, so a multi-ingredient product can say "with Pycnogenol" while supplying far less than the 100 to 200 mg most trials used.

The evidence at a glance

These summaries describe research. They are not claims about what a supplement does. High blood pressure, blood sugar problems, leg swelling, ongoing joint pain and attention problems in children all deserve a clinician's evaluation.

What the Cochrane review found

The anchor document is a 2020 Cochrane review by researchers at Stellenbosch University in South Africa, who declared no conflicts of interest. They set out to gather every randomized trial of any pine bark extract in a chronic condition: 27 trials with 1,641 people across 10 conditions, including heart and blood vessel risk factors, diabetes, knee osteoarthritis, chronic venous insufficiency, erectile dysfunction, asthma and ADHD.

Their conclusions were blunt:

• Certainty was very low for every outcome. Small samples, few trials per condition, varying outcome measures and poor reporting meant that "no definitive conclusions regarding the efficacy or safety" of pine bark extract were possible.
• Supplement makers funded most of the trials. The reviewers wrote that the maker of the tested product funded 20 of the 27 trials. Horphag was named as the funder of at least 13 of them, four of which came to light only after the reviewers contacted the authors. They also noted that publication bias (positive studies getting published while negative ones do not), which is more likely when studies are small, could explain the positive findings.
• Only four trials were at low risk of bias. Of those four, only one tested Pycnogenol on its own: a Swiss trial in people with heart disease, described in the blood pressure section below. One tested a Japanese-made pine bark extract (Flavangenol), one a French extract called Oligopin, and one a multi-ingredient eye formula.
• Several frequently cited studies did not make the cut. The reviewers excluded the best-known erectile function study as quasi-randomized (participants were not assigned purely by chance), a frequently cited menopause study as not a randomized trial, and most of the papers it assessed from the Italian group described next as not randomized trials.

The review covered research up to September 2019. Trials published since then, discussed below, have not changed the overall picture much, and some important new ones were null.

One research group, a lot of studies

A striking share of the Pycnogenol literature comes from a single research group centered on vascular researchers Gianni Belcaro and Maria Rosaria Cesarone, linked to the University of Chieti-Pescara in Italy. A trial disclosure quoted in the Cochrane review describes Belcaro as "a study investigator for Horphag Research," and several of the group's papers include Horphag staff as co-authors.

Here is what the publication record shows, from our search of PubMed on November 1, 2026:

• Volume: 99 of the 587 PubMed records mentioning Pycnogenol, about 17 percent, list Belcaro or Cesarone as authors. Most appeared in the Italian journals Panminerva Medica, Minerva Cardioangiologica, Minerva Medica and Minerva Surgery, and 32 were published in 2020 or later.
• Design: 52 of the 99 papers describe themselves as "registry" studies, in which people taking the supplement plus standard care are compared with a group managed without it, usually chosen rather than randomly assigned. Only 5 abstracts mention randomization and 3 mention double blinding.
• Results: Every one of the 95 abstracts we could read reported a favorable conclusion for Pycnogenol or a product containing it, across conditions as varied as varicose veins, jet lag, tinnitus, hemorrhoids, exam performance in students, restless legs, urinary tract infections and recovery after COVID-19.

Systematic reviewers have repeatedly flagged this design problem. The Cochrane team excluded most of the group's papers that it assessed as not randomized trials. In a 2020 published letter, Italian hypertension researchers criticized a pooled analysis of Pycnogenol for including 9 non-randomized studies that together enrolled more than half of its participants. A 2021 review of supplements sold for air travel symptoms found that only one of four Pycnogenol flight studies, all from this group, was a randomized trial. The pooled swelling effect of the other three was more than five times larger than the review's pooled effects for melatonin on jet lag.

To be clear about what the record does not show: we found no retraction or expression of concern on any of the group's Pycnogenol papers in PubMed or Crossref, searched November 1, 2026. The fair summary is a design problem documented by reviewers. Much of the positive literature comes from one group's open, mostly unrandomized studies, and the better-controlled trials from other teams tend to show smaller effects or none.

Blood pressure and blood vessels

Blood pressure is the most common claim, and it shows the pattern most clearly. The more tightly controlled the analysis, the smaller the effect:

• Double-blind trials only (2020): A meta-analysis of 7 double-blind, placebo-controlled trials with 626 people found no significant effect on systolic, diastolic or mean blood pressure.
• Split by trial quality (2018): A Chinese meta-analysis of 9 trials, 5 of them from the Belcaro group, reported an overall drop of about 3 mmHg systolic. But in its double-blind trials, the drop was about 1 mmHg and not significant, while the open trials showed about 5 mmHg. The authors wrote that the reduction "was not observed in well-designed trials."
• Pine bark extracts in general (2025): A 2025 meta-analysis of 27 trials of several pine extracts (21 of them reporting systolic pressure) found a systolic drop of about 2.3 mmHg. Its authors rated that evidence very low certainty and found signs of publication bias. Six of its trials came from the Belcaro group, and trials at 200 mg a day or more showed essentially no drop (0.24 mmHg, not significant).

The best single Pycnogenol trial came from cardiologists at University Hospital Zurich and was published in the European Heart Journal in 2012. Twenty-three people with coronary artery disease, already on standard treatment, took 200 mg a day or placebo for 8 weeks each, in random order. On Pycnogenol, flow-mediated dilation (how much an artery widens when blood flow increases, a lab measure of blood vessel function) rose from 5.3 to 7.0 percent, while on placebo it went from 5.4 to 4.7 percent. A marker of oxidative stress dipped slightly. But blood pressure, inflammation markers and platelet stickiness did not change. Cochrane rated this trial at low risk of bias. It was supported by an unrestricted grant from Horphag, which also supplied the capsules.

Two trials of other pine bark extracts are worth knowing. A Stanford trial of 130 adults found that 200 mg a day of a Japanese-made French maritime pine bark extract (Flavangenol, funded by its maker) for 12 weeks did not lower blood pressure any more than placebo. A small Spanish trial of Oligopin did not report a blood pressure drop versus placebo. Neither tested Pycnogenol, but both undercut the idea that every pine bark extract lowers pressure.

Our read: Pycnogenol may improve how blood vessels relax, based on one small, well-run trial, but double-blind trials have not shown that it lowers blood pressure. If you are working on your numbers, our magnesium and blood pressure review and blood pressure supplements hub cover options with more consistent data, and nothing replaces prescribed treatment.

Blood sugar and cholesterol

Two small, double-blind, maker-funded trials anchor the blood sugar claims, both in people with type 2 diabetes who kept taking their usual medicines:

• China, 2004: 77 people took 100 mg a day or placebo for 12 weeks. Fasting glucose fell more on Pycnogenol, but the HbA1c difference (a 3-month average of blood sugar) was significant only at the one-month check, not at the end of the trial.
• Arizona, 2008: 48 people who also had high blood pressure took 125 mg a day or placebo for 12 weeks. Fasting glucose fell by 23.7 mg/dL versus 5.7 mg/dL on placebo, and HbA1c by 0.8 versus 0.1 percentage points. Cochrane flagged this trial for possibly reporting only some of the outcomes it measured.

Pooled analyses that combine these with open studies, several from the Belcaro group, report fasting glucose about 6 mg/dL lower and HbA1c about 0.3 points lower. A 2025 umbrella review of supplements for diabetes called the HbA1c evidence for Pycnogenol very low certainty. For cholesterol, results are inconsistent: one meta-analysis of 7 trials found no effect on any blood lipid, another reported a small rise in HDL, and Cochrane's own analysis did not confirm the HDL rise.

Two trials, the Arizona trial and a separate 2004 Chinese trial in people with high blood pressure, reported that some participants needed less of their blood pressure medicine while on Pycnogenol. If you take medicine for blood sugar or blood pressure, that is a reason to involve your doctor before adding it, not a reason to cut your dose on your own.

Knee comfort

Three small trials in people with mild to moderate knee osteoarthritis reported less pain, better function and less use of pain relievers over 3 months:

• Slovakia, 2008: 100 people, 150 mg a day. Pain and function scores improved on Pycnogenol, and the abstract states that placebo had no effect.
• Iran, 2007: 37 people, 150 mg a day. Cochrane noted that the paper's title claimed less stiffness, but its results did not show it.
• Italy, 2008: 156 people, 100 mg a day, from the Belcaro group, which reported a 56 percent improvement in symptom scores versus 10 percent on placebo.

All three were funded by Horphag. A 2018 review in the British Journal of Sports Medicine listed Pycnogenol among supplements with large short-term effects on pain, but that appears to rest on a few small, maker-funded trials. A 2019 evidence panel convened for the US military went the other way and recommended against Pycnogenol for chronic musculoskeletal pain. For other options, see our boswellia vs curcumin review and joint supplement rankings.

Leg swelling, veins and long flights

Pycnogenol is often sold for heavy, swollen legs. Two small trials from 2000, with 40 people each, reported less swelling and heaviness (and, in one, less pain) in people with chronic venous insufficiency (a condition in which leg veins struggle to return blood to the heart) on 300 mg a day. One was double-blind; in the other, only half the patients were randomized and blinded, and they were pooled with the open patients, so the randomized result cannot be separated out.

Nearly everything since then comes from the Belcaro group, mostly open studies, including comparisons in which Pycnogenol beat a European vein medicine and compression stockings. The well-known flight studies, which reported fewer clots and less ankle swelling on long-haul flights, are also from this group, and only one was a randomized trial, with unclear blinding. A small independent Brazilian trial in 30 people with leg ulcers found Pycnogenol performed about the same as a standard flavonoid vein medicine.

The 2022 European Society for Vascular Surgery guideline on chronic venous disease does not mention Pycnogenol. Horse chestnut and diosmin have broader trial bases for leg heaviness, as our circulation hub explains. Sudden swelling or pain in one leg, especially after a flight, needs urgent medical attention, not a supplement.

Attention and behavior in children

Pycnogenol has been tested in children with ADHD, which makes this part of the story especially important to get right. Three trials matter most:

• Slovakia, 2006: 61 children took 1 mg per kg a day or placebo for 4 weeks. The authors reported less hyperactivity and better attention, with symptoms returning a month after stopping. Horphag funded it, and Cochrane rated the evidence very low certainty.
• Belgium, 2022: The largest trial randomized 88 children aged 6 to 12 to Pycnogenol (20 or 40 mg a day by weight), methylphenidate (a standard prescription medicine) or placebo for 10 weeks. It was partly publicly funded, and Horphag supplied, blinded and randomized the treatments under university supervision. On teacher ratings (the placebo group started with somewhat higher scores), total symptom scores fell by about 7.6 points on Pycnogenol, 11.3 on methylphenidate and 1.5 on placebo. But on parent ratings and on inattention, only methylphenidate beat placebo. The trial enrolled 88 of the 144 children it planned, and it could not show that Pycnogenol was as good as the medicine.
• United States, 2002: In a small crossover trial in 24 adults, neither Pycnogenol nor methylphenidate beat placebo over 3 weeks each.

The fair summary: small trials with mixed results, not a replacement for evaluation and treatment. The Belgian trial's own conclusion called Pycnogenol a good alternative to methylphenidate, which goes beyond what its results showed. The UK's NICE guideline on ADHD does not mention it.

Menopause, periods and skin

Menopause. In a Japanese double-blind trial, 170 women around menopause took 30 mg twice a day or placebo for 3 months. Hot flashes and sleep problems improved more on Pycnogenol, although placebo helped a lot too: a standard symptom index fell 56 percent on Pycnogenol and 39 percent on placebo. A frequently cited Taiwanese study using 200 mg a day reported broad improvements but did not report how it compared with placebo in its abstract, and Cochrane listed it as not a randomized trial. For other options, see our menopause supplement rankings.

Period pain. A Japanese double-blind trial in 116 women found no difference in women with mild period pain, and less pain and pain reliever use in women with more painful periods, at 60 mg a day over two cycles.

Skin. A double-blind crossover trial in 76 Beijing outdoor workers found that 100 mg a day (as 50 mg twice daily) for 12 weeks prevented the usual autumn drop in skin hydration. Other skin studies were uncontrolled (20 women in one, 30 in another) or tested Pycnogenol alongside skin creams, and one had two Horphag employees as co-authors. A 2023 double-blind trial in 76 menopausal women reported denser hair on 150 mg a day for 6 months; one author is a Horphag employee.

Sexual function: a combination product

Pycnogenol is often marketed for erections, mostly on the strength of trials of Prelox, a combination of Pycnogenol and L-arginine aspartate. L-arginine is an amino acid with its own blood vessel effects, so these results belong to the combination, not to pine bark alone.

• The best-known study, a 2008 crossover in 50 men, reported restored erectile function and doubled intercourse frequency after a month. Cochrane excluded it as quasi-randomized.
• The largest trial of the combination, 124 men over 6 months, came from the Belcaro group with a Horphag grant. Erectile function scores rose from 15.2 to 27.1 on the combination versus 15.1 to 19.0 on placebo.
• The only trial of Pycnogenol alone that Cochrane included, an independent Slovak study, had 21 men.

Erection problems can be an early sign of heart and blood vessel disease, so they are worth raising with a doctor. Our libido supplements guide and nitric oxide supplement rankings cover related ingredients.

Memory, exercise and long COVID

Memory. An Australian double-blind trial in 101 adults aged 60 to 85 found better working memory after 3 months on 150 mg a day. A much larger 12-month Australian trial, planned to randomize 465 adults to Pycnogenol, the herb bacopa or placebo, published its protocol in 2012 with co-funding from Horphag, but we found no published results for its main outcomes. Most other memory studies are Belcaro-group registries, including one in 87 otherwise healthy adults whose memory test scores fell in a range the authors themselves labeled mild impairment.

Exercise. The endurance claims rest mainly on a Belcaro-group registry study that reported faster triathlon times and better fitness test scores, plus a 9-cyclist trial of a blend that contained Pycnogenol. Neither tells you much.

Long COVID. The Belcaro group published open studies reporting faster recovery after COVID-19. Then a team in Zurich ran one of the most rigorous Pycnogenol trials so far: 153 adults with lingering post-COVID symptoms took 200 mg a day or placebo for 12 weeks, in a quadruple-blind design, the strictest level of blinding. Self-rated health, the main outcome, did not differ between groups, and neither did any secondary outcome. The trial was funded by Horphag, which deserves credit for backing a rigorous test. Its results were posted as a preprint in June 2025 and had not yet been peer reviewed when we checked.

Two other recent trials funded by Horphag educational grants were also underwhelming: a 2026 German trial in 67 women found no difference from placebo in its main bone turnover marker, and a 2025 gum health trial reported differences in a few inflammation markers, though changes within the Pycnogenol group were small and its main outcome, gum bleeding, has not yet been published.

Pycnogenol vs generic pine bark

Store shelves also carry "pine bark extract" at a fraction of Pycnogenol's price, often labeled "95% proanthocyanidins," which sounds stronger than 70 percent. It is not a fair comparison:

• Different trees. Generic extracts often come from other species. One widely sold product, for example, lists Chinese red pine (Pinus massoniana), and some labels name no species at all.
• Different tests. The "95 percent" figure is not the US Pharmacopeia's procyanidin measure, and labels do not say how it was measured, so the two numbers cannot be compared directly.
• Different research. Even a 2024 review written by a Horphag employee says Pycnogenol research cannot be extrapolated to other pine bark extracts. And two other branded pine extracts tested for blood pressure, Flavangenol and Oligopin, showed no effect versus placebo.

Other branded pine extracts, such as Oligopin (also French maritime pine) and Enzogenol (New Zealand's Pinus radiata), have their own smaller research bases. Grape seed extract contains related procyanidins but is a separate product with its own trials. Results should not be transferred from one to another.

Cost

Here is what several products cost at one retailer on November 1, 2026. Prices change and vary by store.

Prices are one-time (not sale) prices from swansonvitamins.com, read November 1, 2026. Cost per day is our arithmetic.

At 100 mg a day, the low end of the usual trial range, Pycnogenol works out to roughly $24 to $33 a month, and roughly $47 to $66 a month at 200 mg. Generic pine bark costs far less, but it is not the extract that was tested.

Safety and how it is regulated

Most trials lasted 1 to 6 months, and Cochrane noted that most did not report serious adverse events or hospital admissions, so long-term safety has not been well studied. We found no published case reports of serious harm in PubMed.

On the regulatory side, Pycnogenol is sold as a dietary supplement. We found no FDA GRAS notice for it; trade press reports a 2003 self-affirmed GRAS determination that was not submitted to FDA. In Europe, a 2010 EFSA opinion found that a cause-and-effect relationship had not been established for antioxidant claims on Pinus pinaster extract, and no pine bark health claim is authorized there. Health Canada's monograph covering pine bark allows antioxidant claims only. In 2000, the Federal Trade Commission alleged that one seller, J & R Research, had made 21 unsubstantiated pycnogenol claims, including that it helped arthritis, ADHD and varicose veins and was "twenty times more protective" than vitamin C. A consent order barred the company from making such claims without scientific support.

Frequently asked questions

What is Pycnogenol?

Pycnogenol is a branded, standardized water extract of French maritime pine bark (Pinus pinaster), sold by Horphag Research. It contains 65 to 75 percent procyanidins, related to the polyphenols in grape seed and cocoa, plus smaller phenolic compounds. It is sold as a dietary supplement and has been tested in many small trials.

Does Pycnogenol lower blood pressure?

Not in double-blind trials. A 2020 meta-analysis of 7 double-blind, placebo-controlled trials found no significant effect, and a 2018 analysis found that the drop seen in open studies disappeared in its double-blind trials. Broader analyses that pool open studies report drops of about 2 to 3 mmHg, rated very low certainty. One small Swiss trial found better blood vessel function without lower blood pressure.

Is Pycnogenol the same as pine bark extract?

No. Pycnogenol is one specific, trademarked extract of French maritime pine. Generic pine bark extracts often come from other pine species and are standardized differently, so their ‘95 percent’ figures are not comparable. Results from Pycnogenol trials cannot be assumed to apply to them, and two other branded pine extracts showed no blood pressure effect versus placebo.

How much Pycnogenol do studies use, and for how long?

Most adult trials used 100 to 200 mg a day, with a range of about 30 to 360 mg, usually for 1 to 6 months. Trials in children used about 1 to 2 mg per kg of body weight, or 20 to 40 mg a day. Products may say ‘with Pycnogenol’ while supplying as little as 20 mg, so check the amount per serving.

Is Pycnogenol safe?

In trials lasting up to about 6 months, side effects were mostly mild, such as stomach upset, dizziness, headache and nausea. Long-term safety has not been well studied, and most trials did not report serious adverse events. It may reduce platelet clumping and has not been studied for bleeding risk alongside blood thinners, it may add to the effects of blood pressure and diabetes medicines, and pregnancy data are minimal. Talk with your doctor first if any of these apply.

Has Pycnogenol been studied for attention problems in children?

Yes, in small trials with mixed results. A 2006 Slovak trial in 61 children reported benefits, and the largest trial, in 88 Belgian children, found improvement on teacher ratings but not on parent ratings or inattention, and it could not show Pycnogenol worked as well as standard medicine. A small adult trial found no effect. It is not a substitute for evaluation and treatment.

The bottom line

Pycnogenol is a well-characterized, standardized extract with a long research list and a reasonable short-term safety record. Look past the length of that list, though, and the core is thin. Most trials were small and maker-funded, much of the positive research comes from one group's open studies, and the independent Cochrane review concluded that no firm conclusions are possible for any condition. Double-blind trials have not shown a blood pressure benefit, and the most rigorous recent trial was null.

The most credible signal is better blood vessel function in one small, well-run Swiss trial, which is a reason for more research rather than a reason to buy. Smaller positive signals for knee comfort, hot flashes and skin hydration come from a handful of double-blind trials, mostly funded by Horphag, and are worth watching. If you decide to try Pycnogenol, choose a product that names the trademark and supplies a studied dose (usually 100 to 200 mg a day), set a time limit, keep expectations modest, and check with your doctor first if you take blood thinners, blood pressure medicines or diabetes medicines.