The nutraceutical combination was found to reduce levels of pain associated with walking and climbing stairs in 40 Japanese people with knee osteoarthritis, according to findings published in the Journal of the Science of Food and Agriculture.
Researchers from Suntory Wellness Ltd, Juntendo University, and three other Japanese research institutes compared the supplement’s efficacy against a placebo, and make no claims about how the addition of quercetin may enhance a traditional glucosamine-chondroitin mix.
The joint health market is dominated by glucosamine. Euromonitor International puts the value of the global market for glucosamine supplements at $2bn, and cites an annual growth rate of 7% from 2004 to 2009.
Clinical trials using glucosamine alone or in combination with chondroitin have yielded conflicting results, leading some medical professionals to question the efficacy of such supplements.
The researchers behind the new study also point to the “ambiguity” in clinical data and note that quercetin has been reported to exert anti-inflammatory effects and may therefore offer joint health potential.
“Tempted” by such observations, the researchers developed a “new glucosamine/chondroitin sulfate-based preparation supplemented with quercetin” for people with osteoarthritis.
According to the Centers for Disease Control and Prevention (CDC), arthritis is the leading cause of disability in the US, affecting some 21 million adults.
This number is predicted to rise to 67 million adults aged over 18 by the year 2030, according to data from the 2003 National Health Interview Survey (NHIS).
Forty people with osteoarthritis were recruited to participate in the new study, and they were randomly assigned to receive a daily placebo or the joint health combination providing 1,200 mg of glucosamine hydrochloride, 60 mg of chondroitin sulfate and 45 mg quercetin glycosides per day.
After 16 weeks of intervention, significant reductions in pain in walking and climbing stairs were recorded in the nutraceutical group, compared to placebo, but no differences between the groups were observed for swelling in the knee joint or the range of motion.
The researchers used criteria from the Japanese Orthopaedic Association to assess joint health symptoms.
Analysis of biomarkers of cartilage metabolism revealed a trend in the balance of synthesis and degradation of type II collagen, said the researchers, but these changes did not reach statistical significance.
“Thus there is the possibility that glucosamine-chondroitin sulfate-quercetin supplement may have some protective effect on the progression of knee osteoarthritis,” said the researchers.
“A long-term clinical trial, in which a sufficient number of subjects with knee osteoarthritis are treated with glucosamine-chondroitin sulfate-quercetin supplement for 6 months or longer periods, will be needed to obtain the answer to this important issue.”
The quercetin used in the new study were actually quercetin 3-(4-O-α-glucosyl)1–6-O-β-glucosides, obtained using an enzymatic process.
“Such enzymatically modified quercetin glycosides have been approved by the governmental authority concerned as a food additive (antioxidant) in Japan and have obtained a credit of GRAS (Generally Recognized as Safe) from the Food and Drug Administration of the USA,” they added.
The joint health market is not limited to glucosamine/chondroitin formulations. Indeed the scientific literature also contains other ingredients with potential joint health benefits, including extracts from French maritime pine bark (Pycnogenol), eggshell membranes (ESM Technologies), seaweed (Marigot and Marinova), and collagen (InterHealth and BioCell).
Source: Journal of the Science of Food and Agriculture
Volume 92, Issue 4, pages 862–869, doi: 10.1002/jsfa.4660
“Effect of a dietary supplement containing glucosamine hydrochloride, chondroitin sulfate and quercetin glycosides on symptomatic knee osteoarthritis: a randomized, double-blind, placebo-controlled study”
Authors: N. Kanzaki, K. Saito, A. Maeda, et al.