What Is the Dietary Inflammatory Index (DII)?
Developed by researchers at the University of South Carolina, the Dietary Inflammatory Index (DII) is a system for scoring foods based on their effect on inflammation in the body. It is a scientifically validated tool used primarily in research to quantify the inflammatory potential of an individual's diet, based on the combined effects of numerous foods, nutrients, and other food components. The index doesn't evaluate single foods in isolation but rather assesses the overall dietary pattern and its potential to either promote or suppress systemic inflammation. The scoring is based on an extensive literature review that links specific dietary parameters to changes in six key inflammatory biomarkers, including C-reactive protein (CRP), Interleukin-6 (IL-6), and Tumor Necrosis Factor-alpha (TNF-α).
How the DII Scoring System Works
Calculating a DII score is a complex process typically performed by researchers or nutrition professionals. It involves collecting detailed dietary intake data, often using a food frequency questionnaire (FFQ) or 24-hour dietary recalls. The score is based on 45 food parameters, including macro and micronutrients, vitamins, minerals, flavonoids, and whole foods.
The scoring process involves these key steps:
- Standardizing Intake: The reported intake of each food parameter is standardized against a global database to express it as a comparative value, or z-score, relative to the average intake worldwide.
- Assigning Scores: Each food parameter is assigned a score based on its known inflammatory effect, derived from the scientific literature review used to develop the index. More negative scores indicate an anti-inflammatory effect, while more positive scores indicate a pro-inflammatory effect.
- Calculating the Overall DII: The standardized intake value for each parameter is multiplied by its effect score. The sum of all these individual scores yields the final, overall DII score for an individual's diet.
A positive DII score indicates a diet with a net pro-inflammatory effect, while a negative score indicates a net anti-inflammatory effect. A score near zero suggests a neutral inflammatory potential. In general, the score ranges from approximately -8.87 (maximally anti-inflammatory) to +7.98 (maximally pro-inflammatory). For more precise comparisons, especially when caloric intake varies widely, an Energy-Adjusted DII (E-DII) is often used.
Pro-inflammatory vs. Anti-inflammatory Foods
Understanding which foods influence your DII score is crucial for managing your dietary inflammatory potential. Generally, diets rich in processed foods, unhealthy fats, and refined sugars tend to have higher, more pro-inflammatory scores, while diets emphasizing whole plant foods, healthy fats, and spices have lower, more anti-inflammatory scores.
Anti-inflammatory foods (Lower DII)
- Fruits and Vegetables: Berries, dark leafy greens (spinach, kale), tomatoes, and beets are rich in antioxidants and vitamins.
- Omega-3 Fatty Acids: Found in fatty fish (salmon, mackerel, sardines), flaxseeds, chia seeds, and walnuts.
- Whole Grains: Oats, brown rice, and quinoa provide fiber that supports gut health and reduces inflammation.
- Healthy Fats: Extra virgin olive oil, nuts, and seeds contain monounsaturated and polyunsaturated fats.
- Herbs and Spices: Turmeric (curcumin), ginger, and garlic have potent anti-inflammatory properties.
- Beverages: Green tea and coffee contain polyphenols and antioxidants.
Pro-inflammatory foods (Higher DII)
- Refined Carbohydrates: White bread, pasta, and baked goods.
- Processed and Red Meats: Bacon, hot dogs, and cured meats.
- Trans Fats: Margarine and processed snacks.
- Sugar-Sweetened Beverages: Soda, sweetened teas, and sports drinks.
- Fried Foods: Items cooked in excessive unhealthy fats.
- Excess Omega-6s: Found in some vegetable oils and processed foods, can lead to an omega-6/omega-3 imbalance.
DII and Health Outcomes
Extensive research has consistently linked higher (more pro-inflammatory) DII scores with an increased risk of various chronic diseases. Meta-analyses and observational studies have found correlations with cardiometabolic disease, certain cancers, and other inflammation-related conditions.
- Cardiovascular Disease (CVD): Higher DII scores are associated with an increased risk of CVD incidence and mortality. This is linked to elevated markers of inflammation and poorer lipid profiles.
- Obesity: Pro-inflammatory diets have been shown to be associated with higher body mass index (BMI), weight gain, and central obesity. This is partly because adipose tissue produces pro-inflammatory cytokines in response to excess calories.
- Metabolic Syndrome: A higher DII score is associated with an increased risk of metabolic syndrome and its components, including hypertension and hyperglycemia.
- Cancer: Higher DII scores have been linked to an elevated risk of overall cancer incidence and mortality, particularly for certain types like colorectal and breast cancer.
- Cardiorespiratory Fitness: Studies indicate an inverse relationship between DII scores and cardiorespiratory fitness, suggesting that a pro-inflammatory diet can negatively affect exercise capacity.
DII vs. Healthy Eating Index (HEI)
While both the DII and the Healthy Eating Index (HEI) evaluate diet, their approaches and purposes differ significantly. The HEI assesses overall diet quality based on adherence to the Dietary Guidelines for Americans, whereas the DII is specifically focused on the inflammatory potential of the diet.
| Feature | Dietary Inflammatory Index (DII) | Healthy Eating Index (HEI) |
|---|---|---|
| Primary Purpose | Quantifies the inflammatory potential of the diet based on how food components affect inflammatory biomarkers. | Assesses adherence to federal dietary guidelines for overall diet quality. |
| Underlying Principle | Links specific dietary parameters (e.g., nutrients, foods) to effects on inflammatory markers like CRP, IL-6, and TNF-α. | Evaluates intake of 13 food components, such as fruits, vegetables, and whole grains, and assesses moderation of items like saturated fat and sodium. |
| Scoring Range | Ranges from approximately -8.87 (most anti-inflammatory) to +7.98 (most pro-inflammatory). | Scored from 0 to 100, with a higher score indicating better diet quality. |
| Standardization | Standardizes individual intake data against a global database to make scores comparable across different studies and populations. | Based on dietary intake guidelines specific to the U.S. population. |
How to Improve Your DII Score
Improving your DII score involves shifting your dietary pattern towards more anti-inflammatory choices. These strategies align with general healthy eating principles and can be implemented gradually.
- Focus on Whole Foods: Prioritize minimally processed, whole foods like fruits, vegetables, legumes, and whole grains.
- Increase Healthy Fats: Incorporate more sources of omega-3 fatty acids and use healthy oils like extra virgin olive oil.
- Embrace Herbs and Spices: Flavor your food with anti-inflammatory powerhouses like turmeric, ginger, and garlic instead of excessive salt or sugar.
- Reduce Processed Intake: Cut back on processed snacks, sugary drinks, and foods high in unhealthy fats and refined carbohydrates.
- Choose Wisely: Opt for leaner protein sources like fish and poultry over processed or high-fat red meats.
For more detailed information on the development and validation of the DII, researchers can explore relevant studies published in scientific journals.
Conclusion
The dietary inflammatory index scoring system offers a robust, research-based method for evaluating the inflammatory potential of a diet. By quantifying the combined effects of dietary components, the DII provides valuable insights into how food choices contribute to or protect against chronic low-grade inflammation. A diet with a low, or negative, DII score is consistently associated with better health outcomes and a reduced risk of chronic diseases such as CVD, obesity, and metabolic syndrome. Focusing on whole, nutrient-dense foods is a powerful strategy to shift dietary patterns toward an anti-inflammatory state and support long-term health.
