2.3. Dietary inflammatory score
The method developed by Shivappa et al was applied to calculate the DIP scores of the diets. The Food Frequency Questionnaire (FFQ) was used to determine the dietary intake [21]. In the Iranian dietary pattern, 29 out of 45 items of DII are very common, including Macronutrients (energy, carbohydrates, fat, protein, fiber), Fat (cholesterol, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA)), Water-soluble vitamins (pyridoxine, folic acid, niacin, thiamin, ascorbic acid and riboflavin). Fat-soluble vitamins (A,D and E), Minerals (iron, magnesium, zinc, and selenium), as well as caffeine, β-carotene, onion, garlic, pepper, and black tea [31]. Other DIP items that were uncommon in the Iranian dietary regimen were omitted form the list of FFQ.
The intake of the above dietary items was adjusted according to the daily energy intake [32]. A z-score was generated for all of the 29 items of the FFQ list for each participant. For each subject, the ”standard global mean” was subtracted from the mean consumed food and divided by “global standard deviation”. The global means and standard deviations were obtained by the method developed by Shivappa et al [21]. To decrease the skewness of the variables, the variables were converted to a centered percentile score. This score was then extended by the impact for every item [21]. The DIP scores of all foods were summed to calculate the overall score. More positive values indicated a higher inflammatory dietary potential.