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.