The role of cherry consumption, either of fresh fruit or of fruit extract, has recently been demonstrated in an epidemiologic study by Zhang et al (1). In the study, gout patients were asked about their food intake 2 days prior to a gout attack (i.e., hazard days) as compared with their food intake during various control periods (one control period at 3, 6, 9, and 12 months after entry into the study). As Gelber and Solomon (2) rightly indicate, the validity of such a study hinges on the accuracy of the recalled dietary consumption. Nevertheless, Zhang et al concluded from their study that cherry intake was beneficial and lowered the incidence of gout by ∼35%.
We used a different approach to demonstrate the efficacy of cherry consumption for the prevention of gout attacks (3–6). The advantage of cherry juice concentrate versus fresh fruit is that it is available throughout the year. In a pilot prospective randomized controlled trial (RCT), which we presented in 2007 (3), patients with gout experienced a significant decrease in the number of acute gout attacks within 4 months of initiating ingestion of the cherry juice concentrate (P < 0.05), an effect that was not seen in the control group ingesting pomegranate juice concentrate. Of patients ingesting cherry juice concentrate, 55% were attack-free and stopped their regular intake of nonsteroidal antiinflammatory drugs within 60 days of initiating consumption of cherry juice concentrate. None of the patients in the group ingesting pomegranate juice discontinued any of their medications.
In our retrospective study of patients ingesting tart cherry juice concentrate daily for ≥4 months (4, 6), a ≥50% reduction in acute gout attacks was seen in approximately half of the patients. Importantly, 36% of patients not receiving urate- lowering therapy were attack-free after 4–6 months of ingesting cherry juice, despite an average serum urate level of 8.7 mg/dl. Thus, although the serum urate level in patients not receiving urate-lowering therapy remained >6 mg/dl, the use of cherry juice concentrate significantly reduced gout attacks. Thus, ingesting tart cherry juice concentrate reduced the incidence of attacks in patients with gout regardless of whether they received urate-lowering therapy.
The mechanism by which cherries and cherry juice concentrate prevent gout attacks is unclear. One of the mechanisms suggested by Gelber and Solomon (2) is the presence of vitamin C in cherries; however, administration of vitamin C has not been found to be as effective for attack prevention. Gouty inflammation is primarily mediated by interleukin-1 (IL-1) (7). Preliminary studies in our laboratory (5, 6) indicate that in vitro treatment with cherry juice concentrate can reduce the release of IL-1 by monocytes activated by monosodium urate crystals.
Our studies suggest that cherry juice concentrate reduces acute attacks of gout when it is consumed over a period of ≥4 months. We have found cherry juice concentrate to have antiinflammatory properties and suggest that it may be useful as prophylaxis for gout. Large, prospective RCTs are needed to further evaluate the efficacy of cherries and cherry juice concentrate for the prevention of attacks in patients with gout.