*Geek Box: The Dietary Inflammatory Index [DII]
The DII was first utilised in 2009 and was based on available research linking diet to one of six inflammatory biomarkers: interleukin-1β [IL-1β], interleukin-4 [IL-4], interleukin-6 [IL-6], interleukin-10 [IL-10], tumour necrosis factor alpha [TNF-a], or CRP.
The DII utilised 45 food parameters based on national food data intakes from different countries across different world regions: Europe, North America, the Middle East, East Asia, South Asia, and Australia. From these data, average intakes of the various food parameters included in the DII were calculated.
As an index of diet, the DII is representing the total dietary pattern. This allows for the overall inflammatory score of an individual’s diet pattern to be quantified, and the overall scores in a cohort can be divided into different levels and analysed in relation to disease outcomes. In the DII, foods associated with positive influences on inflammatory markers – e.g., flavonoids and omega-3 fatty acids – are scored positively. Conversely, foods associated with negative influences on inflammatory markers – e.g., saturated fat and free sugars – are scored negatively.
This is one of the great strengths of dietary indices: they are inherently adaptable to different dietary patterns. More particularly, the use of the DII as a standardised measurement instrument means that the same instrument may be applied across different studies, providing a level of consistency in measuring the exposure-outcome relationship of interest, i.e., DII and CVD or DII and cancer, which is rare for measurement instruments in nutritional epidemiology.