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While the antioxidants in tea may reduce the risk of developing inflammatory diseases, such as rheumatoid arthritis, previous studies have shown inconclusive results.
Regularly consuming tea may lower the risk of developing rheumatoid arthritis (RA), especially for current smokers and in anti-citrullinated autoantibody (ACPA)-positive RA, according to a study published in Arthritis & Research Therapy.1
“In recent years, diet has gained attention for its potential immunomodulatory effects. After water, tea is the most popular drink in the world [and] all kinds of tea are rich in polyphenols, which are antioxidants that may reduce the risk of inflammatory diseases such as RA,” investigators explained. “However, studies on tea consumption and the risk of developing RA have thus far shown inconclusive results.”
Data from the population-based, case-control study, EIRA, was collected for 2237 patients with RA diagnosed between 2005 and 2018 and 4661 controls that were matched for age, sex, and residential area. Participation rate was 90% for the RA cohort and 69% for the controls.
Tea consumption was classified as no (0 cups/day), irregular (< 1 cup/day), regular (1-2 cups/day), and high (≥ 2 cups/day). Herbal tea was classified as no (0 cups/day), irregular (< 1 cup/day), and regular (≥1 cup/day).
Results were adjusted for lifestyle factors, such as smoking habits, alcohol intake, and coffee consumption, as well as body mass index, and educational level.
The control group was more likely to be high consumers of tea when compared with the RA cohort (22.1% vs 19.7%, respectively). In the RA group, 57.3% drank tea and 19.7% were classified into the high tea consumption category. A total of 58.4% of participants in the control group drank tea and 22.1% were high tea consumers. Additionally, those who were tea consumers were less likely to smoke or drink coffee and had a lower alcohol intake. Smoking was more prevalent in the RA cohort (22.5% vs 13.8%).
While tea consumption and risk of RA was not linear, there was a reduction in odds for those who consumed 1 or more cups per day. High consumption was associated with a 22% lower risk when compared with irregular consumers. However, after adjusting for covariates, results were no longer statistically significant. Participants who regularly drank herbal tea had a borderline statistically reduction in risk of developing RA when compared with irregular consumers (adjOR = 0.77, 95% CI 0.58–1.02).
The odds of developing ACPA-positive RA were significantly lower in the high tea consumer group when compared with irregular tea consumers (adjOR = 0.76, 95% CI 0.62–0.94). Lowest odds ratio was seen in current smokers (adjOR = 0.60, 95% CI 0.38–0.95).
The study was strengthened by the participation rates and study design. However, tea consumption data was missing for a large percentage of participants, which investigators chose to classify in the no tea consumption group. This notion was backed up by the fact that proportion of tea drinkers was in line with Swedish statistics on tea sales. Irregular tea consumption was used as a reference. Recall bias may have altered the results of the study; however, it was not believed to have impacted the amount of missing data as percentages were similar in both the RA cohort and the control group.
“This study showed an inverse association with the risk of RA among high tea consumers compared to irregular consumers among smokers and in the ACPA-positive subset of RA,” investigators concluded. “We could not draw any conclusion about no tea consumption and the risk of RA, due to the possibility of bias.”
Westerlind H, Palmqvist I, Saevarsdottir S, Alfredsson L, Klareskog L, Di Giuseppe D. Is tea consumption associated with reduction of risk of rheumatoid arthritis? A Swedish case-control study. Arthritis Res Ther. 2021;23(1):209. Published 2021 Aug 7. doi:10.1186/s13075-021-02583-y