BIRMINGHAM, ENGLAND – Proinflammatory diets are associated with increased C-reactive protein (CRP) and subsequent rheumatoid arthritis (RA), according to combined data from the European Prospective Investigation of Cancer and Nutrition (EPIC) and Norfolk Arthritis Register (NOAR).
Sara Freeman/MDedge News
Dr. Max Yates
“There has always been a debate around this topic,” Max Yates, MBBS, PhD, said at the annual conference of the British Society for Rheumatology. “A quick online search will reveal a plethora of texts claiming to give definitive or the best advice for arthritis” and diet, he said, often from “questionable experts.”
“I think we’re all interested in diet,” observed Dr. Yates, of the University of East Anglia in Norwich (England), and “although the association between diet and arthritis is open to debate, previous studies have shown an association with those who have a lower intake of vitamin C and fiber.” The problem is one of credibility, he noted, so this was something that the NOAR investigators decided to look into with data from the Dietary Inflammatory Index (DII) collected from the EPIC cohort.
The DII is a literature-based, population-derived tool that has been used to determine the inflammatory potential of diet, Dr. Yates explained. Data show that inflammatory diets are is associated with increased levels of inflammatory markers including C-reactive protein (CRP) and interleukin (IL)-6. These diets include items such as trans and saturated fats, and fats from animal protein versus more anti-inflammatory items such as black tea, thyme, turmeric, and saffron.
“We are fortunate that NOAR is in the same geographic location as EPIC,” Dr. Yates said, and the two cohorts have been running alongside each other since the early 1990s. While NOAR has been collecting data on incident inflammatory polyarthritis since 1989, EPIC has been “intensively” collecting information on dietary and lifestyle factors and blood samples from its participants since 1993.
EPIC investigators have been “trailblazers” in recording of dietary data, Dr. Yates said. First using paper-based questionnaires and now smartphone apps that allow people to upload photos of what they are eating. Data are linked to both primary care practice and hospital records.
For the present study, data on 159 patients who participated in both NOAR and EPIC were used. Participants had RA according to the 2010 American College of Rheumatology criteria and had an average disease onset of 7 years after enrollment into NOAR and EPIC.
“Quite pleasingly, the dietary inflammatory index scores were associated with high-sensitivity CRP taken at baseline enrollment in 1993 to 1997, further validating the index again within another population,” Dr. Yates said.
Results showed that there was a significant association between the baseline DII score and subsequent development of RA, with an odds ratio of 1.90 comparing individuals with the highest and lowest DII scores (P less than .01).
When cases were matched by age, sex, and body mass index, however, there was only a trend for an association between inflammatory diets and RA onset. “We hope to identify more patients within EPIC to strengthen this association,” Dr. Yates said.
The results are consistent with data from the Nurses’ Health Study, Dr. Yates noted, adding that future research is needed to address whether dietary modification can demonstrate causality.
“Diet is one of the modifiable risk factors that we can use to tackle RA, and I think it’s about time we as a community take over this area and gave definitive advice.”
Dr. Yates presented the work on behalf of PhD student Ellie Sayer. Neither Dr. Yates nor Ms. Sayer had any conflicts of interests to disclose.
SOURCE: Sayer E et al. Rheumatology. 2019;58(suppl 3), Abstract 014.