Pine Bark Extract: Fertility, Testosterone and More

Summary: Pine bark extract (best known as Pycnogenol) has been tested in dozens of small human trials, but a Cochrane review found the evidence too weak to draw firm conclusions for any condition. The most interesting results are for sperm quality and erectile function, yet most of those studies were small, short and used pine bark combined with L-arginine. Effects on testosterone, skin and blood sugar look small at best, and blood pressure results are mixed.

Pine bark extract is sold for everything from fertility and erections to smoother skin and healthier blood sugar. If you’ve searched for it, you’ve probably seen bold claims. Here we look at what the human studies actually found, how strong that evidence is, and what to know about safety before you try it.

What is pine bark extract?

Pine bark extract is made from the bark of pine trees. The most studied version is Pycnogenol, a trademarked, standardized extract of French maritime pine (Pinus pinaster) bark. It’s mostly made of procyanidins, which are chains of plant compounds called flavonoids (the same family found in tea, cocoa and berries), plus smaller plant acids such as ferulic acid [1]. In lab and animal research, these compounds act as antioxidants (they mop up unstable molecules that can damage cells) and help blood vessels relax [1].

That sounds promising, but lab results don’t always carry over to people. A 2020 Cochrane review, which pooled 27 randomized trials with about 1,600 people across 10 conditions, rated almost all of the evidence as “very low certainty.” The reviewers concluded that small studies and poor reporting mean “no definitive conclusions” about how well pine bark extract works, or how safe it is, are possible yet [2]. Memorial Sloan Kettering Cancer Center’s herb database also describes the evidence as limited [3].

Pine bark extract and fertility

Fertility is one of the most common reasons people look up pine bark extract. Nearly all the research is in men with poor sperm quality:

• Pycnogenol alone: 19 men with low fertility took 200 mg a day for 90 days. The share of normally shaped sperm (after a lab preparation step) rose by 38%, and a test of the sperm’s ability to bind to an egg improved by 19%. There was no placebo group, so we can’t tell how much was due to the extract [4].
• Pycnogenol with L-arginine: in a placebo-controlled crossover trial (each man tried both the supplement and a dummy pill), 50 infertile men took Prelox, a mix of pine bark extract and L-arginine aspartate, for one month. Semen volume, sperm count, movement and shape all improved compared with placebo, but the gains disappeared after the men stopped taking it [5].
• A Japanese study of 47 men with low sperm count and movement found sperm concentration roughly doubled after 2–4 months of L-arginine plus 60 mg of Pycnogenol. It compared results before and after treatment rather than against a placebo [6].

Two important caveats: none of these studies reported whether couples actually got pregnant, and the combination trials can’t tell us how much was due to pine bark and how much to L-arginine, an amino acid the body uses to make nitric oxide.

For women, the evidence is thinner still. In one Japanese study of 58 women who’d had surgery for endometriosis (a painful condition where tissue like the lining of the womb grows outside it), 60 mg of Pycnogenol a day slowly reduced symptoms, though less strongly than a standard hormone drug. It didn’t change estrogen levels or menstrual cycles, and fertility wasn’t measured [7]. We couldn’t find any trials of pine bark extract for egg quality or IVF success, or good safety data for use while trying to conceive or during pregnancy.

Does pine bark extract raise testosterone?

Only a little, if at all, and only in studies where it was combined with L-arginine:

• In a one-month crossover trial of 50 men with erectile dysfunction, blood testosterone rose significantly while taking Prelox [8].
• In a 6-month trial of 124 men aged 30–50, average total testosterone went from 15.9 to 18.9 nmol/L with Prelox, versus 16.9 to 17.3 nmol/L with placebo. That’s an increase of about 19%, and both groups started in the normal range [9].
• An 8-week Japanese trial of Pycnogenol with L-arginine and aspartic acid saw only a slight rise in testosterone measured in saliva [10]. (Aspartic acid is related to D-aspartic acid, which is itself sold as a testosterone booster.)

When a 2023 meta-analysis (a study that pools the results of several trials) combined three of these trials with 184 men, the pine bark and L-arginine combination did not raise testosterone significantly compared with the control groups [11]. So the honest summary is that pine bark extract is not a meaningful testosterone booster.

Pine bark extract for erectile dysfunction

This is where the most consistent results are. The trials above all found better scores on the International Index of Erectile Function (IIEF), a standard questionnaire, in men with mild to moderate erectile dysfunction [8,9,10]. In the 6-month trial, the erection score rose from about 15 to 27 (out of 30) with Prelox, compared with about 15 to 19 with placebo [9]. The 2023 meta-analysis also found improvements in erectile function, orgasm and satisfaction [11].

Still, independent reviewers are cautious. The Cochrane review rated the erectile dysfunction evidence as very low certainty [2]. A 2026 review by French urology and sexual medicine societies found only “modest low-certainty signals” for Pycnogenol and concluded the evidence doesn’t support routinely recommending herbal products for erectile dysfunction [12]. Prelox is made by Horphag Research, the company behind the Pycnogenol trademark [9], and most of these trials were small and short. If erections are a problem, it’s worth seeing a doctor, because erectile dysfunction can be an early sign of heart or blood vessel disease.

Other pine bark extract benefits: skin, blood sugar and more

Skin. In 20 healthy postmenopausal women, 12 weeks of Pycnogenol (25 mg three times a day) improved skin hydration and elasticity, especially in women who had dry skin to start with. Skin samples showed more activity of genes involved in making hyaluronic acid and collagen, two molecules that keep skin plump [13]. The study was small and had no placebo group, so treat this as early evidence.

Blood sugar. A 2019 meta-analysis of 24 trials found Pycnogenol lowered fasting blood sugar by about 6 mg/dL and HbA1c (a measure of average blood sugar over about three months) by about 0.3 percentage points [14]. Those are small changes. Individual trials in people with type 2 diabetes reported larger drops [15,16], and lab tests suggest the procyanidins may slow the enzyme that breaks carbohydrates down into sugar in the gut [17]. The Cochrane reviewers still rated the diabetes evidence as very low certainty [2].

Blood pressure. Results are mixed. One meta-analysis of 24 trials found a small drop of about 2.5/1.8 mmHg [14], while another that included only the seven best-designed, double-blind placebo-controlled trials (626 people) found no effect on blood pressure at all [18]. In a 12-week trial in people with mild high blood pressure, 100 mg a day helped people lower their dose of a blood pressure medicine (nifedipine) [19]. Pine bark extract shouldn’t replace prescribed treatment.

Memory. In 101 healthy adults aged 60–85, 150 mg a day for three months modestly improved working memory compared with placebo and lowered a blood marker of oxidative damage [20]. This hasn’t been widely repeated.

You may also see claims about asthma, ADHD, vein problems and joint pain. The Cochrane review found only one to three small trials for each, all rated very low certainty [2].

How much pine bark extract is used in studies?

There’s no official recommended dose. The trials in this article used between 60 mg and 200 mg of Pycnogenol a day, for anywhere from a few weeks to about a year [4,7,13,15,19,20]. Many products sold as “pine bark extract” use other pine species or extraction methods, so results from Pycnogenol studies may not apply to every product on the shelf.

Pine bark extract side effects and safety

In clinical trials, pine bark extract has usually been well tolerated. When side effects occur, they tend to be mild, such as stomach upset, dizziness, headache and nausea [1,19]. Most trials were short and didn’t report serious side effects well, so long-term safety isn’t known [2]. Some things to be aware of:

• Blood thinners: pine bark extract may reduce blood clotting, so it could raise bleeding risk if you take warfarin or other anticoagulant or antiplatelet medicines [3].
• Diabetes and blood pressure medicines: because it may lower blood sugar and blood pressure slightly [14,19], check with your doctor if you take medicine for either.
• Allergy: don’t take it if you’re allergic to pine bark [3].
• Pregnancy and breastfeeding: there isn’t enough safety research, so it’s best avoided unless your doctor advises otherwise.

The bottom line on pine bark extract

Pine bark extract is one of the more studied plant extracts, but most of that research is small, short and often linked to the manufacturer. The strongest signals are for sperm quality and erectile function, mostly with pine bark combined with L-arginine, and even those are rated low or very low certainty [2,12]. It doesn’t meaningfully raise testosterone, and its effects on blood sugar, skin and blood pressure are small or uncertain.

If you’re trying to conceive, a fertility specialist can check for treatable causes first. If you still want to try pine bark extract, choose a product that names its extract and dose clearly, and run it past your doctor, especially if you take blood thinners or diabetes medicine. For more on popular men’s health supplements, see our reviews of ashwagandha and L-citrulline.

This article is for general information only and isn’t medical advice. Talk to your doctor or another qualified health professional before starting a new supplement. See our medical disclaimer.

References

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2. Robertson NU, Schoonees A, Brand A, Visser J. Pine bark (Pinus spp.) extract for treating chronic disorders. Cochrane Database Syst Rev. 2020;9(9):CD008294. https://doi.org/10.1002/14651858.CD008294.pub5
3. Memorial Sloan Kettering Cancer Center. Pine Bark Extract. About Herbs, Botanicals & Other Products. Updated August 3, 2023. https://www.mskcc.org/cancer-care/integrative-medicine/herbs/pine-bark-extract
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