Inflammation is a natural biological process where the immune system responds to injury, infection, or irritation. While acute inflammation is beneficial for healing, chronic, low-grade inflammation that persists over time can be detrimental to health. Diet plays a substantial role in modulating this chronic inflammatory state, as foods consumed can either promote or reduce inflammation within the body. The Dietary Inflammatory Index (DII) is a scientific tool developed to quantify this relationship.
Understanding the Dietary Inflammatory Index (DII)
The Dietary Inflammatory Index is an advanced exposure assessment tool designed to estimate the inflammatory potential of a person’s overall diet. Developed by researchers at the University of South Carolina, the DII provides a standardized, continuous measure of diet-related inflammation. Its primary goal is to move beyond simple food group analysis and provide a single, universal score that can be compared across different populations and studies worldwide.
The index is calculated based on an individual’s reported intake of specific food components, typically derived from a food frequency questionnaire. The score is rooted in an extensive review of scientific literature linking various dietary factors to six key inflammatory biomarkers. These biomarkers include C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-\(\alpha\)).
The DII provides a score that ranges from highly anti-inflammatory to highly pro-inflammatory. Its design allows researchers to compare diet-inflammation relationships across diverse global populations. This standardized approach provides a robust metric for understanding the link between dietary habits and systemic inflammation.
Components and Scoring of the DII
The calculation of the DII typically incorporates up to 45 different food parameters. These components include specific vitamins, minerals, fatty acids, and phytochemicals, not just whole foods. Anti-inflammatory elements include fiber, magnesium, omega-3 fatty acids, and vitamins A, C, and E. Pro-inflammatory components that drive the score upward include saturated fat, trans fat, and refined carbohydrates.
The scoring methodology involves a multi-step mathematical process to ensure consistency. First, an individual’s intake of each parameter is compared to a global mean intake derived from multiple international datasets. This comparison is then standardized and converted into a centered percentile score.
Each parameter is assigned an inflammatory effect score based on scientific literature, indicating its known ability to modulate inflammation. The standardized intake of each parameter is multiplied by its respective inflammatory effect score, and all results are summed to generate the final DII score. A highly negative DII score signifies a diet with strong anti-inflammatory properties. Conversely, a highly positive score indicates a predominantly pro-inflammatory diet.
Translating the DII Score into Dietary Choices
The DII score translates directly into practical dietary patterns that individuals can adopt. A low (negative) DII score is characterized by a high intake of nutrient-dense, whole foods rich in compounds that actively suppress inflammation. This pattern closely mirrors the Mediterranean diet, which has been shown to significantly reduce DII scores.
To achieve a more anti-inflammatory score, the focus is on foods high in fiber, antioxidants, and healthy fats. This includes regular consumption of fruits, vegetables, and legumes, which are excellent sources of anti-inflammatory phytochemicals. Key components are sources of omega-3 fatty acids, such as fatty fish, and spices like turmeric, ginger, and garlic, which have high anti-inflammatory potential. Using monounsaturated fats like extra virgin olive oil as the primary cooking fat also contributes to a lower DII score.
In contrast, dietary patterns that result in a high (positive) DII score are typically high in components that promote systemic inflammation. These patterns align with a Western-style diet characterized by overconsumption of highly processed and refined foods. Foods that increase the DII score include red and processed meats, sugar-sweetened beverages, and refined grains. A high intake of solid fats, such as those found in fried foods and many baked goods, also drives the DII score into the pro-inflammatory range. These items are high in saturated fat and simple carbohydrates, which are known to increase inflammatory markers in the body.
Research Applications and Health Outcomes
The DII serves as a valuable tool in epidemiological research, allowing scientists to investigate the long-term impact of dietary patterns on disease risk. By quantifying the inflammatory potential of a diet, researchers can more accurately model the link between food and chronic health conditions. The DII has been used in hundreds of studies and forms the basis for numerous meta-analyses exploring diet-disease associations.
Research consistently shows that a higher, more pro-inflammatory DII score is associated with an increased risk of developing several chronic diseases. These include cardiovascular disease, certain types of cancer, and metabolic disorders like type 2 diabetes and metabolic syndrome. Conversely, individuals with a low, anti-inflammatory DII score generally demonstrate a reduced risk for these same conditions. This suggests that dietary choices quantified by the index have measurable consequences for long-term health and mortality.