Dietary Inflammatory Index (DII) - Diet and Inflammation

What is the Dietary Inflammatory Index?

The Dietary Inflammatory Index (DII) is a scientifically validated scoring system that quantifies the inflammatory potential of an individual's diet. It was developed in 2014 by Shivappa and colleagues at the University of South Carolina, drawing on data from more than 1,900 peer-reviewed publications. Each dietary component is assigned a score reflecting its pro-inflammatory or anti-inflammatory properties, and the individual scores are combined into a single overall DII value.

A high positive DII score indicates a predominantly pro-inflammatory diet, while a negative DII score reflects a predominantly anti-inflammatory diet. Because chronic low-grade inflammation is recognized as a major contributor to many non-communicable diseases, the DII has become an important tool in nutritional epidemiology and preventive medicine.

Background and Development

Chronic, low-grade inflammation is closely linked to the development of numerous modern diseases, including cardiovascular disease, type 2 diabetes, certain cancers, and metabolic syndrome. Diet is considered one of the most modifiable factors influencing systemic inflammation.

The DII was created to make this relationship measurable and to allow researchers and clinicians to evaluate dietary patterns according to their effect on key inflammatory biomarkers such as C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha).

How the DII is Calculated

The DII is calculated using dietary intake data collected via methods such as 24-hour dietary recalls or validated food frequency questionnaires. Up to 45 dietary parameters are assessed, including:

• Macronutrients (e.g., carbohydrates, fats, protein)
• Micronutrients (e.g., vitamin C, vitamin D, zinc, magnesium)
• Bioactive compounds (e.g., flavonoids, isoflavones, capsaicin)
• Other dietary components such as fiber, caffeine, and alcohol

Each parameter is assigned a weighted inflammation score based on the available scientific evidence. The sum of all weighted scores produces the final DII value for an individual.

Pro-Inflammatory and Anti-Inflammatory Dietary Components

Pro-Inflammatory Factors (increase the DII score)

• Saturated fatty acids
• Trans fatty acids
• Refined carbohydrates and added sugars
• High consumption of red and processed meat
• Excessive alcohol intake

Anti-Inflammatory Factors (lower the DII score)

• Omega-3 fatty acids (e.g., from oily fish, flaxseed oil)
• Dietary fiber (e.g., from vegetables, legumes, whole grains)
• Antioxidants such as vitamin C, vitamin E, and beta-carotene
• Polyphenols and flavonoids (e.g., from berries, green tea)
• Spices such as turmeric, ginger, and garlic
• A Mediterranean-style dietary pattern overall

Clinical Relevance and Research Findings

A growing body of epidemiological evidence has linked a high (pro-inflammatory) DII score with increased risk for a range of health conditions:

• Cardiovascular disease: A higher DII is associated with elevated CRP levels and greater risk of coronary heart disease and stroke.
• Type 2 diabetes: Pro-inflammatory dietary patterns are linked to insulin resistance and an increased risk of developing diabetes.
• Cancer: Meta-analyses have reported associations between a high DII and increased risk of colorectal, breast, and gastric cancers.
• Obesity and metabolic syndrome: An inflammatory diet contributes to chronic low-grade inflammation, which is closely linked to overweight and obesity.
• Depression and mental health: Emerging research suggests a higher DII may be associated with an increased risk of depressive disorders.

Practical Application

While the DII is primarily used in research settings, it is increasingly being applied in clinical nutrition practice. Physicians and dietitians can use it to:

• assess an individual's dietary inflammation risk profile,
• provide tailored dietary recommendations to reduce inflammation,
• support the management of chronic inflammatory conditions through nutrition.

A Mediterranean diet, a plant-based dietary pattern, and the targeted intake of anti-inflammatory nutrients are recognized as effective strategies for lowering the DII score.

Limitations of the DII

Despite its usefulness, the DII has certain limitations that should be taken into account:

• It relies on self-reported dietary data, which can be subject to recall bias and measurement error.
• Not all 45 dietary parameters are captured in every dietary assessment instrument.
• Individual differences in metabolism, gut microbiota composition, and genetics are not accounted for.
• The DII measures associations rather than direct causal relationships.

References

1. Shivappa N, Steck SE, Hurley TG, Hussey JR, Hebert JR. Designing and developing a literature-derived, population-based dietary inflammatory index. Public Health Nutrition. 2014;17(8):1689-1696.
2. Hebert JR, Shivappa N, Wirth MD, Hussey JR, Hurley TG. Perspective: The Dietary Inflammatory Index (DII) - Lessons Learned, Improvements Made, and Future Directions. Advances in Nutrition. 2019;10(2):185-195.
3. Minihane AM, Vinoy S, Russell WR, et al. Low-grade inflammation, diet composition and health: current research evidence and its translation. British Journal of Nutrition. 2015;114(7):999-1012.