Pycnogenol Data Too Sparse to Support Chronic Disease Use

Janis C. Kelly

February 23, 2012

February 23, 2012 — Studies regarding Pycnogenol (Horphag Research), a dietary supplement extracted from the bark of pine trees grown only in Landes de Gascogne, France, provide insufficient support for its use, according to a systematic review of randomized controlled trials published online February 15 in the Cochrane Database of Systematic Reviews.

The supplement has lately become popular for the prevention and treatment of several chronic disorders, write Anel Schoonees, from the Division of Human Nutrition, Stellenbosch University, Tygerberg, Western Cape, South Africa, and colleagues in their review, which they prepared on behalf of the Cochrane Collaboration.

The reviewers conclude that "currently available evidence [about Pycnogenol] is not sufficient to support claims regarding its benefit in any chronic condition. Furthermore, the available evidence provides no assurance regarding the safety of Pycnogenol."

The main ingredient in the supplement is procyanidin, a powerful antioxidant also found in grapes, berries, pomegranates, red wine, and some nuts. Procyanidin, a subtype of proanthocyanidin, has attracted research attention because of the possibility that reducing oxidative stress by lowering levels of reactive oxygen species might be beneficial in diseases such as cardiovascular disease, rheumatic disorders, cancer, inflammatory bowel disease, Alzheimer's disease, Parkinson's disease, and cataracts.

Although supplements containing proanthocyanidin are sold worldwide under a variety of different trade names, the reviewers focused on Pycnogenol because it is "a standardized product widely marketed for its antioxidant effects."

The reviewers note, "The manufacturer of Pycnogenol strongly promotes research and claims that its products are based on results of scientific research."

The Cochrane reviewers searched CENTRAL, MEDLINE, EMBASE, and 3 trial registries for randomized controlled trials evaluating the effectiveness of Pycnogenol in adults or children with any chronic disorder. They also contacted the manufacturer of the supplement and hand-searched the bibliographies of included studies. Chronic disorders were defined as a disease such as heart disease, stroke, cancer, diabetes, or HIV/AIDS, or a nonspecific illness such as fatigue or pain, of more than 3 months' duration.

Primary outcomes were clinical outcomes directly related to the disorder and all-cause mortality.

Fifteen trials involving a total of 791 participants met the criteria for inclusion in the review. These included 2 studies in asthma (n = 86), 1 study in attention-deficit/hyperactivity disorder (n = 61), 2 studies in chronic venous insufficiency (n = 60), 4 studies in diabetes mellitus (n = 201), 1 study in erectile dysfunction (n = 21), 2 studies in hypertension (n = 69), and 3 studies in osteoarthritis (n = 293).

The authors write, "Despite the positive findings reported in a number of studies in this review, small sample size and constraints to conducting meta-analyses and poor study quality preclude firm conclusions regarding the effects of Pycnogenol."

Perhaps the most important limitation was the small sample size of the studies, which can lead to misleading conclusions because of the role of chance. Outcomes for each disorder varied widely across the studies, so results from different studies could not be pooled.

Data quality was also a problem. "In some cases outcomes were not measured in an optimal manner. For example, in one study of hypertension, systolic and diastolic blood pressure were not reported directly but by the change in drug (nifedipine) dosage at the end of the treatment period," the authors write.

With regard to quality of the evidence, the reviewers found problems such as lack of allocation concealment, incomplete blinding, and selective outcome reporting. Furthermore, they warn that publication bias is more likely with small studies and could explain the positive findings in the reported trials.

"A further concern was that 11 of the 15 trials were funded by the manufacturer of the test drug," the authors write.

They conclude, "Well-designed, adequately powered randomized controlled trials of Pycnogenol are needed. Careful attention should be given to the outcomes to be assessed in future trials to ensure that selected outcomes are important to patients and are measured in a standardized manner."

The authors have disclosed no relevant financial relationships.

Cochrane Database Syst Rev. Published online February 15, 2012. Abstract

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