Effects of Dietary Habits on Markers of Oxidative Stress in Subjects with Hashimoto’s Thyroiditis: Comparison Between the Mediterranean Diet and a Gluten-Free Diet

Background: The Mediterranean diet (MedD) exerts anti-inflammatory and anti-oxidant effects that are beneficial in autoimmune thyroid diseases (ATD). Recently, a gluten-free diet (GFD) has been proposed for non-celiac patients with Hashimoto’s thyroiditis (HT), but its usefulness is under debate. The present pilot study evaluates the effects of these two dietary regimes, with a focus on redox homeostasis, in HT. Patients and Methods: 45 euthyroid HT patients (30 F; median age 42 years) were randomly assigned to different dietary regimes: MedD (n = 15), GFD (n = 15) and free diet (FD, n = 15). Thyroid function tests, autoantibodies, and oxidative stress markers (Advanced glycation end products, AGEs; glutathione peroxidase (GPx), thioredoxin reductase (TRxR), and total plasma antioxidant activity (TEAA) were measured at baseline and after 12 weeks. Results: In the MedD group, significantly lower values of AGEs and higher values of GPX, TRX and TEAA with anti-oxidant action were detected (p < 0.05) at 12 weeks compared to baseline, and compared to the GFD and FD groups, in which the oxidative stress parameters did not change significantly (p > 0.05). No significant differences in serum levels of TSH, FT4, Ab-Tg, Ab-TPO compared to baseline were found in any group. Conclusions: This pilot study confirms the protective effect of the MedD against oxidative stress, while a GFD does not significantly influence markers of oxidative stress and/or thyroid autoimmunity/function parameters.