Efficacy of Spice Supplementation in Rheumatoid Arthritis: A Systematic Literature Review

Background: Spices, i.e., curcumin, ginger, saffron, and cinnamon, have a thousand-year history of medicinal use in Asia. Modern medicine has begun to explore their therapeutic properties during the last few decades. We aimed to perform a systematic literature review (SLR) of randomized controlled trials (RCTs) assessing the effect of spice supplementation on symptoms and disease activity in patients with chronic inflammatory rheumatic diseases (rheumatoid arthritis (RA), spondylarthritis, or psoriatic arthritis). Methods: An SLR of RCTs, reviews, and meta-analyses was performed, searching for articles in MEDLINE/PubMed. Abstracts from international rheumatology and nutrition congresses (2017–2020) were also scrutinized. The risk of bias of the selected studies was evaluated using the Cochrane Collaboration’s tool and the Jadad scale. Results: Altogether, six studies, assessing the use of spice supplementation only in RA patients, were included: one on garlic supplementation, two on curcumin, one on ginger, one on cinnamon, and one on saffron supplementation. Garlic, ginger, cinnamon, or saffron supplementation was associated with a decrease in RA clinical activity. However, several points limit the external validity of these studies. No conclusion on the impact of curcumin supplementation on RA activity could be drawn due to low-quality studies. Conclusions: Garlic, ginger, cinnamon, and saffron supplementation could have a beneficial effect on RA activity, but the risk of bias of these studies is difficult to assess and data are too limited to recommend them in daily practice.