Medha Barbhaiya, MD, of the Hospital for Special Surgery in New York City, and colleagues suggest that compared with women who scored in the lowest tertile of the 2010 Alternative Healthy Eating Index those in the highest tertile had no significant decrease in risk, with a hazard ratio of 0.78 (95% CI 0.54-1.14, P=0.23).
According to the researchers, there was also no difference found in risk depending on whether the individual was seropositive for anti-double-stranded (ds)DNA antibodies (HR 0.78, 95% CI 0.45-1.36) or seronegative (HR 0.78, 95% CI 0.46-1.31).
While many studies have demonstrated lower risks of rheumatoid arthritis with healthy diets such as the AHEI-2010 the association of overall dietary pattern has been studied very little in SLE. Despite the little research mechanistic rationales exists for considering diet as a potential influence on SLE as the team explains, “Oxidative stress and other environmental exposures, including diet, can contribute to lupus onset and flares through epigenetic mechanisms that modify CD4+ T cell gene expression.”
In this study, data was analyzed from the 2 Nurses’ Health Studies including 79,568 women who were enrolled in the first study and 93,554 who were enrolled in the second study. All participants filled out food frequency questionnaires every 4 years and were rated on adherence to three dietary quality scores. AHEI-2010 was based on Dietary Guidelines For Americans and includes 11 foods that are considered as being healthy and others that are considered unhealthy; scores ranged between 0 as the worst to 110 as the best.
The modified Mediterranean Diet was the second diet which measures 9 components of foods that are considered to be healthy as well as undesirable components with scores ranging from 0 to 9. The third diet was the DASH Diet which is similar to the Mediterranean Diet but with scores ranging from 8 to 40. The fourth diet was the Empirical Dietary Inflammation Index which rates food groups according to plasma inflammatory biomarkers levels which contained 9 food groups that are considered to be pro-inflammatory and nine others that are considered to be anti-inflammatory.
The analysis was adjusted for multiple factors including age, race, income, smoking status, BMI, alcohol use, and menopausal status. There were 194 incident cases of SLE with 91 being anti-dsDNA positive and 1-3 being anti-dsDNA negative. Participant mean age was 50, mean BMI was 25 and more than 90% of the participants were caucasian.
According to the researchers in the multivariable analysis, there was no significant difference in SLE risk for the averaged highest versus the lowest tertiles of scores on the 3 scores other than the AHEI-2010: The Mediterranean diet, HR 0.82 (95% CI 0.56-1.18); DASH diet, HR 1.16 (95% CI 0.81-1.66); and Dietary inflammatory index, HR 0.83 (95% CI 0.57-1.21). Additionally, there were no differences according to anti-dsDNA status on any of the scores or in baseline.
The only lower risk that was identified was on the cumulative average intake of nuts and legumes in the AHEI-2010 with a hazard ratio for SLE of 0.59 (95% CI 0.40-0.87, P=0.006) for the highest versus lowest tertile.
“Nuts and legumes are a rich source of alpha-linoleic acid, an anti-inflammatory polyunsaturated fat associated with reduced risk of inflammation and cardiovascular disease,” the researchers explained, adding that the 41% decreased risk for SLE seen with high intake of nuts and legumes should be investigated further.
The study was limited by the possibility of recall bias with the food questionnaire, and that it was not powered to evaluate interactions between diet and other potential risk factors. The researchers suggest that they may not have been able to detect associations between dietary quality and SLE because there may have been changes in secular trends in lifestyle and diet over the period of the studies, and that diet in early life may be more influential.
“Our findings warrant replication in large, prospective, general population cohorts, with younger participants and increased racial/ethnic variation,” Barbhaiya and co-authors concluded.
