Healing Tool Series: Empirical Dietary Inflammatory Index

An index to assesses diet quality based on its inflammatory potential.

“Healing Tools” summaries are a collection of evidence-based resources to help providers and patients use integrative health approaches to improve health and wellbeing.

This tool is for: Providers

This tool was created by: Researchers from Harvard T.H. Chan School of Public Health, Brigham and Women’s Hospital, Harvard Medical School, Dana–Farber Cancer Institute, and Massachusetts General Hospital

SUMMARY

What is this tool for?

Chronic inflammation plays an important role in the development of many chronic diseases, and some dietary patterns have been shown to be associated with inflammation. The researchers developed and validated an empirical dietary inflammatory index (EDII) to assess diet quality based on its inflammatory potential.

The EDII is the weighted sum of 18 food groups: 9 are anti-inflammatory and 9 are pro-inflammatory.

Anti-inflammatory food groups:

• Beer
• Wine
• Tea
• Coffee
• Dark yellow vegetables
• Leafy green vegetables
• Snacks
• Fruit juice
• Pizza

Pro-inflammatory food groups:

• Processed meat
• Red meat
• Organ meat
• Other fish (other than dark-meat fish)
• Other vegetables (other than leafy green vegetables and dark yellow vegetables)
• Refined grains
• High-energy beverages
• Low-energy beverages
• Tomatoes

Methods

Researchers developed the EDII by entering 39 food groups in reduced rank regression models and performing stepwise linear regression analyses on dietary and inflammatory markers data from the Nurses’ Health Study (NHS, n = 5230 women). They evaluated 3 plasma inflammatory markers, using data from previously collected blood samples:

• Interleukin-6 (IL-6)
• C-reactive protein (CRP)
• Tumor necrosis factor α receptor 2 (TNFαR2)

The inflammatory markers were measured through:

• IL-6 and TNFαR2: Enzyme-linked immunosorbent assay
• CRP: A high-sensitivity immunoturbidimetric assay

Based on the analyses, the researchers identified 18 of the 39 food groups as significant contributors to the EDII.

In evaluating the construct validity of the EDII, researchers also used data from the Nurses’ Health Study II (NHS-II) and the Health Professionals Follow-up Study (HPFS).

Researchers used data on diet, medical history, and health practice from questionnaires completed by NHS, NHS-II, and HPFS participants.  They calculated an inflammation-related chronic disease comorbidity score by summing the presence or absence of certain chronic diseases and conditions: hypercholesterolemia, cancer, diabetes, high blood pressure, heart disease, and rheumatoid or other arthritis.

Validation of the EDII

Researchers evaluated the construct validity of the EDII using data from the NHS-II (n = 1002 women) and the HPFS (n = 2632 men) and conducted sensitivity analyses using six potential alternative versions of the EDII. Using multivariable-adjusted linear regression models, they evaluated how well the EDII predicted concentrations of IL-6, CRP, TNFαR2, adiponectin, and an overall inflammatory marker score for all biomarkers.

More details on the EDII

Complete details of the development and validation of the EDII are available in “Development and Validation of an Empirical Dietary Inflammatory Index,” Journal of Nutrition. 2016 Aug; 146(8): 1560–1570.

How can providers use this tool?

Providers can use the EDII to assess the inflammatory potential of a patient’s overall diet and provide counseling, as appropriate, on a healthier diet.

Diet recommendations: For overall health, the most tested diets are the Mediterranean Diet and the DASH Diet. They have benefits for a variety of conditions. Providers can point patients to resources on the Harvard School of Public Health website at https://www.hsph.harvard.edu/nutritionsource/. They have tested tools and recipes for health and reducing risk of disease.

DASH

Designed to prevent and lower high blood pressure, DASH recommends foods high in certain nutrients (potassium, calcium, protein, and fiber): vegetables, fruits, whole grains, fat-free or low-fat dairy products, fish, poultry, beans, nuts, and vegetable oils. The diet limits salt, saturated fat, and sugar.

Mediterranean diet

This heart-healthy diet is based on the typical foods and recipes of people in Mediterranean countries. It emphasizes fruits, vegetables, nuts, olive oil, fish and other healthy foods and limits red meat, sugar, and saturated fat.

Other diets also on the U.S. News 2018* list of Best Diets Overall include:

Flexitarian Diet

This primarily vegetarian diet gives people the flexibility to eat meat sometimes.  Beginners can start with 2 meatless days per week (up to 26 ounces of meat or poultry per week) while experts go at least 5 days a week with no meat (9 ounces of meat or poultry per week).

Weight Watchers

This diet uses a SmartPoints® system that encourages people to eat more fruits, vegetables, and lean protein, and less sugar and unhealthy fats. Weight Watchers offers support through in-person meetings, online chat, or telephone).

* The U.S. News Best Diets Overall is based on ratings by an expert panel comprised of nutritionists, specialists in diabetes and heart disease, and other diet experts.

How does this contribute to an integrative approach?

Integrative health involves combining conventional medicine, self-care, and complementary and alternative medicine to help patients achieve optimal healing, health and wellbeing.. A healthier diet can be made part of self-care and applying a lifestyle medicine approach to chronic disease.

What does the evidence say about this tool?

Researchers found strong construct validity for the EDII in women and men, indicating its usefulness in assessing the inflammatory potential of whole diets. The EDII significantly predicted concentrations of all biomarkers in the NHS-II and HPFS samples. For example, the relative concentrations comparing extreme EDII quintiles were:

• In NHS-II :
  • Adiponectin: 0.88 (95% CI, 0.80, 0.96), P-trend = 0.003
  • CRP: 1.52 (95% CI, 1.18, 1.97), P-trend = 0.002
• In HPFS:
  • Adiponectin: 0.87 (95% CI, 0.82, 0.92), P-trend < 0.0001
  • CRP: 1.23 (95% CI, 1.09, 1.40), P-trend = 0.002

The EDII also circumvents a major limitation of dietary pattern studies because it can be calculated in a standardized and reproducible manner across different populations.

Limitations:

The study had several limitations:

• The mostly white study population in the NHS, NHS-II, and HPFS, requires further study in multiethnic/multiracial populations
• Only one measurement of the inflammatory markers tended to underestimate validity assessed by correlation coefficients.
• Potential confounding factors were self-reported food intake and residual confounding is possible.

What are the drawbacks to using this tool?

There are no resources or tools for asking patients about their diets in relation to the 9 anti-inflammatory and 9 inflammatory foods, and few specific resources or tools for providers to give patients about a healthier diet. One resource to consider giving patients is the following integrative health guide which includes information on healthy food options.

Who created this tool?

A group of researchers from four institutions created this tool.

Researchers:

• Fred K. Tabung
• Stephanie A. Smith-Warner
• Jorge E. Chavarro
• Kana Wu
• Charles S. Fuchs
• Frank B. Hu
• Andrew T. Chan
• Walter C. Willett
• Edward L. Giovannucci

Institutions:

• Harvard T.H. Chan School of Public Health and Harvard Medical School
• Brigham and Women’s Hospital
• Dana–Farber Cancer Institute
• Massachusetts General Hospital 

For the affiliations of each author, see “Development and Validation of an Empirical Dietary Inflammatory Index.”

Funding:

Jorge E. Chavarro and Frank B. Hu were supported by NIH grants P30DK046200 and U54 CA155426.

The Health Professionals Follow-Up Study, Nurses’ Health Study, and Nurses’ Health Study II cohorts are supported by NIH grants UM1 CA 167552, UM1 CA 186107, and UM1 CA 176726, respectively.

For more information click here.

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