This case-control study investigates the related between DTAC and Rheumatoid Arthritis. Our study suggests that DTAC may potentially reduce the risk of RA. In the present study, participants in the lowest tertile of DTAC had a significantly OR for rheumatoid, compared with those in the highest tertile and this result persisted after adjustment for potential confounders including BMI; physical activity; waist circumference; smoking; and dietary intake energy and fat.
To our knowledge, this is the first attempt to evaluating associated between DTAC and risk of RA in new diagnosis patients, although evidence have suggested that oxidative status affects the severity and activity of RA. Several previous studies have shown an inversely association between the Dietary TAC and inflammatory diseases such as MS, ulcerative colitis, cardiovascular diseases (18), cancer (28), diabetes, metabolic disorders (16) which share common metabolic parameters with RA.
Several studies showed an inverse relation between intake of antioxidant micronutrients and foods rich in antioxidants with risk of RA(29, 30). The healthy diet and Mediterranean diet are rich in natural antioxidants, which are determined by abundant amounts of plant foods including whole grains, fruits, vegetables, olive oil, legumes, herbs and spices, demonstrated an inverse relationship with risk of RA, as well as an inverse association in chronic diseases associated with RA (31–34). However, in a cohort study, this inverse relationship was found only in vegetables and citrus fruits (29). Also, a number of studies have shown the ability of other nutrients rich in antioxidant to reduced oxidative stress and subsequently reduced risk of rheumatism including garlic, ginger, quercetin, green tea and pomegranate (3, 19–22). Also, in our study, several nutrients that have antioxidant activity have shown an inverse relationship with risk for RA. Fruit, vegetable, n-3 fatty acid, MUFA, fiber and folic acid can be mention. However, in a prospective cohort of older women, there was no relation between coffee as an antioxidant-rich nutrient and incident RA(35). This may be due to the lack of precise control of potential confounders such as tea in this study. So that, decaffeinated tea was associated with an increased risk of developing RA that his increased risk could be due to a lack of caffeine .also, it is possible that other chemical ingredients utilized in the growing or preparation of tea are responsible for this observation(35). In addition, when considering the effects of antioxidant-rich nutrients, one should pay attention to their various synergistic effects, which are also present in DTAC. Also, this suggests that a natural balance between dietary antioxidants can be used to prevent RA compared to certain supplements that may lead to an imbalance of the complex antioxidant system through excessive antioxidant consumption and its side effects, be more effective.
One of the mechanisms that seems to play a role in preventing the onset of RA by receiving dietary antioxidants is the prevention of the production of 8-hydroxydeoxyguanosine from DNA damage by inhibiting the production of ROS(36). In addition, in various studies, antioxidant compounds such as α-tocopherol, β-carotene, and ascorbic acid have been implicated in blocking the activation of the nuclear transcription factor kB (NF κB), which is involved in the regulation of several "pre-inflammatory" genes, decreases the inflammatory response(37). On the other hand, some antioxidant compounds, such as vitamin E, can reduce anti-inflammatory response by inhibiting the arachidonic acid pathway, which is responsible for synthesizing pre-inflammatory prostaglandins and leukotrienes(38). Fruits and vegetables are rich in antioxidants and also major sources of fiber(39). Increased fiber intake reduces the time spent in the intestine and lessens the absorption of harmful compounds in the gut, thereby reducing serum levels of these harmful compounds in RA. By reducing the amount of these toxic compounds, patients' health can improve(40). On the other hand, inflammatory condition such as obesity and the consumption Western diet can increase the risk of rheumatism. They exert their effects through the production of cytokines and chemokine which increased risk of RA.
Strengths and Limitations
To the best of our knowledge, this is the first study that evaluated the association between evaluating dietary total antioxidant capacity and newly diagnosed RA patients. Additionally, we have selected new diagnosed patients to reduce the likelihood of diet changes. We controlled the effects of several potential confounders in the statistical analyses.
Also, our study encounters a number of limitations, including: relatively small sample size and evaluating dietary patterns by using a self-reported 1-year FFQ which may increase the possibility of error in measuring dietary intake The subjects we studied were only from Isfahan, thus we cannot extend these results to all Iranians or the worldwide peoples. It should be mentioned that results may have been influenced by some potential confounders that were not assessed, such as genetic and stress level.