Individuals with medically diagnosed knee osteoarthritis (OA) participated in a randomized, double-blind study to investigate the effects of a high-rosmarinic acid (rosA) spearmint tea. Sixty-two participants were randomized by sex and screening pain score to consume tea brewed from a high-rosA spearmint variety or a commercially available spearmint twice daily for 16 weeks. Pain, quality of life (QoL), and physical function at baseline and week 16 were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short-Form 36-item Health Survey (SF-36), 6-minute walk test (6MWT), and stair climb test (SCT). Data from 46 participants (mean age=60.7; BMI=32.9 kg/m(2)) were analyzed. Pain score significantly decreased from week 0 to 16 for the high-rosA group but not for the control group and scores for stiffness and physical disability significantly decreased from week 0 to 16 for both groups. Increased QoL score on the bodily pain index in the SF-36 was observed at week 16 within the high-rosA group only, although no significant differences were observed between the groups. A nonsignificant improvement was observed in the 6MWT at week 16 in the high-rosA group only. There were no changes in the SCT for either group. Therefore, 16-week daily consumption of the high-rosA and commercial spearmint teas significantly improved stiffness and physical disability scores in adults with knee OA, but only the high-rosA tea significantly decreased pain. Consumption of high-rosA tea warrants further consideration as a potential complementary therapy to reduce pain in OA.
Clinical trial registration number: NCT01380015.
Keywords: 6-minute walk test; WOMAC; knee osteoarthritis; pain; rosmarinic acid; spearmint tea.