vegetables. Certain foods — such as fish, olive oil, moderate amounts of alcohol, and vegetables — can be healthy choices for prevention of rheumatoid arthritis. Alternatively, other foods like red meat and sugary drinks can increase RA risk. But new research discourages thinking of individual foods in isolation and indicates that a diet combining the healthy foods can be more protective against RA than the sum of its parts.

“The major message from the current study is that each of these healthy food items may only confer modest beneficial effects,” says Yang Hu, lead author of the study

. “Consuming them together can maximize their protective effects against RA.”

[For more information about how diet can impact RA, check out this CreakyJoints explainer.]

Previous studies had investigated associations between individual foods or drinks and risk for RA, notes Hu, a science doctoral candidate in the Harvard School of Public Health’s nutrition program. “But the findings for these analyses are not always consistent,” she says.

Hu accounts for the inconsistent findings with the hypothesis that each food and nutrient only offers a small benefit and that broader advantages could only be discernible when healthy foods are working together in concert. So she and her colleagues used the 2010 Alternative Healthy Eating Index (AHEI) to determine whether overall quality of a diet related to RA risk.

Greater adherence to the AHEI has been associated with lower risks of major chronic diseases, such as coronary heart disease, stroke, and type 2 diabetes.

“Since the pathological pathways are overlapped between these diseases and RA, it’s not surprising to observe a similar protective effect in RA,” Hu says. “On the other hand, unlike these major chronic diseases, few dietary factors have been consistently associated with risk of developing RA.”

In the study, Hu and colleagues worked with data from 75,597 women aged 30 to 55 who were included in the Nurses’ Health Study (1976), as well as another 93,392 women aged 25 to 42 who were part of the Nurses’ Health Study II (1989). The researchers found that a better quality diet was associated with lower RA risk for women 55 years old and under, while it lacked a significant association for women over the age of 55.

“The age 55 years is not a magic turning point that could dramatically alter your risk of RA,” Hu says. “It’s rather an empirical cutoff found in the analyses.”

Researchers don’t yet understand completely why a healthy diet is more of a factor in whether younger rather than an older women develop RA, but Hu notes that previous studies have found that factors such as body mass index (BMI), diabetes, hyperlipidemia, hypertension, and smoking tend to impact cardiovascular diseases less as patients grow older.

“This is likely due to blunted response to autonomic nervous system stimuli that is triggered by these modifiable factors,” Hu says.

Prior research also indicates etiological (causal) differences between RA that occurs in younger and older people.

“It is proposed that later onset RA may be different from earlier onset RA in terms of genetic predisposition and immune dysfunction, and hormonal changes with menopause can be a source of RA activation in older female patients,” Hu says. “Thus, it’s likely that the early and later onset RA have somewhat different etiological pathways. But the mechanisms of why diet quality is only associated with risk of early onset of RA still needs further investigations.”

While Hu and her colleagues’ study focuses more on the role the index AHEI plays in preventing RA rather than treating it, there are still important takeaways for patients.

Studies have associated eating a Mediterranean diet with improved physical function and vitality, but it’s not known if the AHEI would similarly improve RA symptoms, Hu says. And she advises physicians to inform patients that they ought to improve the quality of their diets overall, rather than just singling out one or the other food item.

In future research, Hu intends to investigate more population-based studies (to confirm these findings), whether there are dietary patterns that are more relevant to RA development prevention, and if the quality of the diet could modify RA risk that is based upon genetic predispositions.