Moreover, the randomised, double-blind, placebo-controlled trial involving 37 patients with osteoarthritis and using the pine bark extract, Pycnogenol, indicated an improvement in physical function of 52 per cent.
The study is published in the journal Nutrition Research .
"To our knowledge, this is the first randomised clinical trial to show the effectiveness of Pycnogenol, a dietary supplement with known antioxidant and anti-inflammatory activities, in alleviating the clinical symptoms of knee osteoarthritis," wrote the researchers, led by Ronald Ross Watson from the University of Arizona.
Osteoarthritis effects about seven million people in the UK alone are reported to have long-term health problems associated with arthritis.
Around 206m working days were lost in the UK in 1999-2000, equal to £18bn (€26bn) of lost productivity.
The new study randomly assigned the volunteers (average age 48.2, average BMI 23.1 kg per sq. m) to receive either a daily dose of Pycnogenol (150 mg) or placebo for three months.
Using the Western Ontario and McMaster Universities (WOMAC)
Osteoarthritis Index as a measure of arthritis symptoms, the researchers report that pain and physical function scores improved after 60 and 90 days of supplementation with the pine bark extract.
No changes were observed in the placebo group.
Furthermore, after 90 days of Pycnogenol supplementation the WOMAC scores for self-reported pain, stiffness, and physical function were reduced by 43, 35, and 52, respectively.
Changes in the use of Nonsteroidal anti-inflammatory drugs (NSAIDs) or selective cyclooxygenase 2 (COX-2) inhibitors were also observed between the groups.
Before the study started, all the patients reported requiring NSAIDs or COX-2 inhibitors on most days.
Subjects in the pycnogenol group reported a significant reduction in the monthly intake of NSAIDs and COX-2 inhibitor pills in terms of the number of pills and number of days, compared to the baseline.
Subjects in the placebo group reported a marked increase in the number of days and pills taken.
"The results of this study indicate the efficacy of Pycnogenol in alleviating osteoarthritis symptoms and reducing the need for NSAIDs or COX-2 inhibitors administration," wrote the researchers.
While no mechanistic study was performed by the researchers, Watson and co-workers do propose that the beneficial effect of the pine bark extract might be due to its antioxidant and anti-inflammatory properties.
The researchers called for further research to clarify the underlying mechanism.
They also recommended that larger clinical trials be conducted in osteoarthritic patients.
The study was supported by a grant from Horphag Research, the company behind the Pycnogenol ingredient.
The company has been very active in sponsoring and supporting studies into the potential health benefits of the pine bark extract.
The first research was conducted on the ingredient 35 years ago.
Victor Ferrari, research chief operating officer and executive vice president of Horphag Research, told NutraIngredients last year that the company ploughs $1.5m - "most of its profits" - into research each year.
The product is extracted from the bark of the Maritime pine that grows on the southern coast of France, and is currently used in over 400 dietary supplements, multi-vitamins and health products.
Source: Nutrition Research (Elsevier) November 2007, Volume 27, Issue 11, Pages 692-697 "Pycnogenol supplementation reduces pain and stiffness and improves physical function in adults with knee osteoarthritis" Authors: R. Farid, Z. Mirfeizi, M. Mirheidari, Z. Rezaieyazdi, H. Mansouri, H. Esmaelli, S. Zibadi, P. Rohdewald and R.R. Watson