Women who follow a Mediterranean-style diet – high in whole grains, nuts, fish, and legumes while low in red meats, processed meats, and saturated fats – showed no significant reduction in the risk of developing rheumatoid arthritis in a large, prospective cohort study.
However, the findings do not jibe with the results of other studies in which the diet was associated with a reduced risk of certain other inflammatory diseases or observations of clinical improvement in people with existing rheumatoid arthritis (RA).
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A Mediterranean diet does not appear to reduce the risk of developing rheumatoid arthritis.
The study, published Sept. 23 in Arthritis Care and Research (doi:10.1002/acr.22481), evaluated data from nearly 175,000 women in two U.S. cohorts: the 1980-2008 Nurses Health Study (n = 83,245) and the 1991-2009 Nurses Health Study II (n = 91,393). Data from both cohorts were obtained through validated diet questionnaires at baseline and every 4 years during follow-up. Investigator Yang Hu of Brigham & Women’s Hospital, Boston, and his colleagues, identified 913 incident cases of RA in 3.5 million person-years of follow-up and found the pooled hazard ratio for women in the quartile most adherent to the Mediterranean diet to be 0.98 (95% confidence interval, 0.80-1.20; P for trend = .85), compared with women in the quartile representing the lowest level of adherence.
The investigators described nine measures they used to assess the Mediterranean dietary pattern, including consumption of vegetables (not potatoes), fruits, nuts, whole grains, legumes, fish ratio of monounsaturated to saturated fats, red and processed meats, and alcohol. When components of the Mediterranean diet were evaluated as separate contributors to risk, only alcohol consumption was seen significantly associated with RA risk, with moderate consumption linked to lower risk.
Two coauthors of Mr. Hu and his colleagues’ study detailed the alcohol-related findings from the same cohort in a paper earlier this year (Arthritis Rheumatol. 2014;66:1998-2005). Mr. Hu and his colleagues hypothesized that the null findings related to the Mediterranean diet could have been influenced by the fact that within the food categories used in the study (fats, vegetables, fish), certain preparations or types of food might contribute to risk while others might help lower it.
The study was supported by grants from the National Institutes of Health. None of the authors declared conflicts of interest.