Food is considered as important environmental factor that plays a role in development of Hashimoto's thyroiditis (HT). The goal of our study was to identify food groups, assessed by food frequency questionnaire, that differ in consumption frequency between 491 patients with HT and 433 controls. We also analysed association of food groups with the wealth of HT-related clinical traits and symptoms. We found significantly increased consumption of animal fat (OR 1.55, p < 0.0001) and processed meat (OR 1.16, p = 0.0012) in HT cases, whereas controls consumed significantly more frequently red meat (OR 0.80, p < 0.0001), non-alcoholic beverages (OR 0.82, p < 0.0001), whole grains (OR 0.82, p < 0.0001) and plant oil (OR 0.87, p < 0.0001). We also observed association of plant oil consumption with increased triiodothyronine levels in HT patients (β = 0.07, p < 0.0001), and, association of olive oil consumption with decreased systolic blood pressure (β = − 0.16, p = 0.001) in HT patients on levothyroxine (LT4) therapy. Analysis of food consumption between HT patients with and without LT4 therapy suggest that patients do not tend to modify their diet upon HT diagnosis in our population. Our study may be of relevance to nutritionists, nutritional therapists and clinicians involved in developing dietary recommendations for HT patients. Environmental factors, in addition to genetic factors, play important role in Hashimoto's thyroiditis (HT) development 1. HT is a chronic autoimmune thyroid disorder (AITD) characterized by the production of thyroid autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) 2. Other main characteristics of HT include infiltration of lymphocytes and ruination of thyroid tissue, which usually leads to hypothyroidism 3. This disease predominantly affects female population and is considered as one of the most frequent endocrine disorders 4. The estimated incidence of HT is 350/100,000 for females and 80/100,000 per year for males 5. It is most often diagnosed in women between the age of 30 and 60 6. High iodine intake (median urinary iodine concentration ≥ 300 μg/L) 7 , especially in areas with sufficient iodine supply, is one of the most known factors that increase the incidence of HT 8. Also, low vitamin D levels (below 30 ng/mL) 9 and low selenium intake (bellow 40 µg/day) 10 are proposed to be risk factors for HT development, albeit a role of these factors in HT still needs to be confirmed. Conversely, alcohol intake was proposed to decrease the risk for HT 11. Other dietary factors are also considered as potential environmental modifiers of the clinical appearance of HT 12-15. A diet low in gluten has been recently proposed to have beneficial effects on the disease course in a study of 34 women with HT 13. Another study of 83 patients with HT indicated that restriction of lactose intake in lactose-intolerant HT patients resulted with decreased thyroid-stimulating hormone (TSH) levels 14. However, the current knowledge of this topic is scarce and only the following two studies ...