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Rheumatoid arthritis (RA) affects women more than men, and risk is influenced by a number of environmental and genetic factors, including diet. It was diet specifically that recently led a team of U.S.-based investigators to examine the impact of diet on RA risk among participants in the Women鈥檚 Health Initiative (WHI), a prospective cohort study focused on prevention and management of chronic diseases in postmenopausal women.¹

When it comes to diet, oily fish containing long-chain omega-3 polyunsaturated fatty acids, as well as moderate alcohol use, vegetables, and olive oil, have all been associated with lower risk of developing RA. Red meat and sugar-sweetened sodas, on the other hand, increase the risk of RA. However, the impact of overall dietary patterns on RA risk hasn鈥檛 been well studied in large populations, the authors note.

How the study was designed

In the current prospective study, Malani and colleagues tracked the incidence of RA in 109,591 postmenopausal women (average follow-up time 8.1 years) in terms of diet quality, as measured by the Healthy Eating Index (HEI)-2015 total score.¹ Secondary objectives included the relationship between incident RA and intake of food groups or nutrients that align with the components of either the HEI-2015 or the Alternative Healthy Eating Index-2010.

This study was part of the WHI and included participants recruited at a number of clinical centers in the U.S. between 1993 and 1998. A food frequency questionnaire was utilized to measure diet at baseline. The association between self-reported, physician-diagnosed RA and diet quality was analyzed using multivariable Cox proportional regression that adjusted for age, race, ethnicity, education status, income, and body mass index.

There are 13 components to the HEI-2015, including 9 for which adequate intake is recommended and 4 in which limited intake is recommended. A higher HEI-2015 score corresponds with a higher quality diet and vice versa. Subjects were stratified evenly into quartiles (n=27,398 in each group, minus 1 woman in quartile 1) depending on their HEI-2015 score, and to each food group/nutrient, based on the total score or the total food group/nutrient intake.

Fruit and veggies are good, fats are bad

A total of 5823 incident RA cases were identified during a follow-up of 857,517 person-years. Compared with quartile 1 of the HEI-2015, which corresponded with the lowest quality diet score, the adjusted total scores for quartiles 2, 3, and 4 were associated with a 1%, 10%, and 19% lower risk of RA, respectively (P trend <.001). Lower incident RA rates were also associated with more consumption of total fruits (P trend = .014), whole fruits (P trend <.0002), total vegetables (P trend = .008), greens and beans (P trend <.0002), whole grains (P trend = .008), and dairy (P trend = .018). By comparison, significantly higher rates of RA were associated with consumption of saturated fat (P trend = .002).

Even given the depth and breadth of these findings, the study nevertheless had some limitations, including the following:

• The results relied on self-reported responses, which may lack accuracy in terms of dietary habits.
• The research team used only a single point in time when measuring diet.
• Some patients with osteoarthritis may have misreported their disease status as RA.
• Current ethnic and racial diversity in the U.S. may not be reflected by the 1993 WHI cohort, even though, at the time, the WHI oversampled for African-American and Hispanic women.
• Incident RA in the enrollment period of 1993 to 1998 may not reflect current levels of incident RA.
• The results are limited to a population consisting of postmenopausal women.

Clinicians who treat RA: don鈥檛 forget about diet!

Despite these issues, Malani and colleagues say their study puts an important focus on diet in the diagnosis and management of RA.

鈥淥ur findings suggest that future RA risk algorithms could benefit from incorporating diet quality as a key factor, given the significant relationship between higher diet quality and decreased RA risk,鈥� says lead investigator Kanika Malani, Warren Alpert School of Medicine at Brown University, Providence, R.I. 鈥淎dditionally, management guidelines may emphasize the importance of a diet rich in fruits, vegetables, legumes, whole grains, and dairy while reducing saturated fat, particularly for postmenopausal women, to help lower the risk of developing RA.鈥�

Malani noted a number of potential areas for additional research to build upon these findings. 鈥淔uture studies may benefit from measuring specific seromarkers associated with RA to have a more objective measurement of RA status,鈥� she and her colleagues wrote.¹

Randomized controlled trials comparing healthy and unhealthy diets would also be valuable in validating these results, Malani says. 鈥淎dditionally,鈥� she concluded, 鈥渇urther research on diet quality and RA among other populations is warranted to determine if these findings are consistent across different cohorts.鈥�

Published: September 23, 2024