The Dietary Inflammatory Index (DII) is a numerical score created by researchers to assess the inflammatory potential of a person's diet. It is based on a comprehensive literature review of how various dietary components and foods affect key inflammatory biomarkers in the body. A more positive DII score indicates a diet with a higher pro-inflammatory potential, while a more negative score reflects a diet that is more anti-inflammatory. This tool has become an important metric for studying the complex link between diet, inflammation, and chronic diseases like cardiovascular disease, diabetes, and cancer.
How is the DII Calculated?
The calculation of a DII score is a multi-step process conducted by nutrition researchers, not a simple at-home tool. It begins with data collected from an individual's diet, typically through a food frequency questionnaire (FFQ) or 24-hour dietary recalls. This data is then used to determine the intake levels of up to 45 different food parameters, including specific nutrients, vitamins, minerals, and whole foods.
- Standardization: The individual's intake of each food parameter is standardized into a 'Z-score' by comparing it to a global average derived from eleven different countries. This step ensures comparability across diverse populations by normalizing dietary intake data.
- Percentile Scoring: The Z-score is converted into a centered percentile score, ranging from -1 to +1, to minimize statistical skewness. A score of +1 represents the most pro-inflammatory intake, -1 the most anti-inflammatory, and 0 is neutral.
- Literature-Based Weighting: Each food parameter is assigned a specific inflammatory effect score based on an exhaustive review of scientific literature published between 1950 and 2010. The literature scores are adjusted for the robustness of the evidence.
- Final Score Aggregation: The individual's percentile score for each dietary component is multiplied by its literature-derived inflammatory effect score. These parameter-specific scores are then summed up to generate the overall DII score for that individual.
Interpreting Your DII Score
For a professional calculation of the DII, the final score provides a quantifiable measure of the diet's potential to either promote or reduce inflammation. It is not an endpoint in itself but a guide for intervention and risk assessment.
- Positive DII Score: A positive score indicates a more pro-inflammatory diet. This is typically associated with a higher consumption of processed foods, refined carbohydrates, added sugars, and saturated or trans fats. High DII scores have been linked to an increased risk of obesity, metabolic syndrome, and cardiovascular disease.
- Negative DII Score: A negative score indicates a more anti-inflammatory diet. This pattern is characterized by higher intake of fruits, vegetables, whole grains, and foods rich in omega-3 fatty acids, fiber, and polyphenols. A lower DII score is generally associated with a reduced risk of chronic diseases.
Anti-Inflammatory vs. Pro-Inflammatory Foods
To better understand the DII, it is helpful to categorize foods based on their general impact on inflammation, though the actual index uses far more granular data.
| Table: Anti-Inflammatory vs. Pro-Inflammatory Foods | Category | Anti-Inflammatory Foods (Lower DII) | Pro-Inflammatory Foods (Higher DII) |
|---|---|---|---|
| Fruits | Berries, apples, cherries, oranges | Fruit juices with added sugar | |
| Vegetables | Leafy greens (spinach, kale), tomatoes, broccoli | Starchy white potatoes in large amounts | |
| Fats | Omega-3 rich fish (salmon, tuna), flaxseeds, olive oil | Trans fats (margarine, microwave popcorn), Saturated fats | |
| Grains | Whole grains (oats, brown rice, quinoa) | Refined grains (white bread, white pasta, pastries) | |
| Spices | Turmeric, ginger, garlic | N/A | |
| Processed Items | N/A | Processed and red meats, packaged snacks | |
| Beverages | Green and black tea, coffee | Sugar-sweetened beverages (soda, sweetened tea) |
Health Implications of the DII
The DII serves as a tool to evaluate the connection between dietary patterns and long-term health outcomes. A high DII score is associated with an increased risk of numerous chronic, low-grade inflammatory conditions, while a low score is protective.
- Cardiovascular Disease (CVD): Higher DII scores correlate with increased CVD risk and mortality. This is linked to elevated markers such as C-reactive protein (CRP) and unfavorable cholesterol and triglyceride levels.
- Metabolic Syndrome and Type 2 Diabetes: Meta-analyses have consistently found that a more pro-inflammatory diet (higher DII) is associated with a higher risk of metabolic syndrome and type 2 diabetes. Key indicators like hyperglycemia and insulin resistance show strong associations with higher DII scores.
- Cancer: Evidence suggests that higher DII scores are associated with an increased risk for several types of cancer, including colorectal, pancreatic, and breast cancers. The link is thought to involve chronic inflammation's role in tumorigenesis.
- Mental Health and Cognitive Function: Emerging research is exploring the relationship between DII and mental health, with some studies suggesting a link between a pro-inflammatory diet and depression. A healthy dietary pattern with a low DII can positively impact mental well-being.
Limitations and Considerations of the DII
While a valuable research tool, the DII is not without limitations. It is complex to calculate and primarily used in epidemiological studies rather than for individual clinical assessment. Furthermore, the DII is based on a global standard and may not perfectly capture the nuances of regional diets. The index also primarily focuses on the inflammatory aspect of diet and should be considered alongside other established dietary quality indices, such as the Healthy Eating Index (HEI). A balanced perspective acknowledges the tool's utility in research while recognizing that practical dietary changes focus on increasing whole, unprocessed foods and reducing refined and processed items.
Conclusion
The Dietary Inflammatory Index is a robust, research-backed metric for quantifying the inflammatory potential of a person's diet. By assigning positive scores to pro-inflammatory dietary components and negative scores to anti-inflammatory ones, the DII provides a powerful tool for studying the link between nutrition and chronic disease. A higher, positive DII score is consistently associated with an increased risk of conditions like CVD and metabolic syndrome, while a lower, negative score is protective. Ultimately, the DII reinforces the importance of moving towards a diet rich in whole, plant-based foods and healthy fats to manage systemic inflammation and promote long-term health.
For more in-depth information on the methodology and development of the DII, readers can consult the scientific literature, such as the publication by Shivappa et al. in Public Health Nutrition that details the tool's creation and validation.
