The report is a product of the VA/HSR Evidence Synthesis Program.

Beyond Diabetes, Obesity, and Cardiovascular Disease: An Evidence Map of Anti-Inflammatory Diet and Related Dietary Interventions for the Prevention and Management of Chronic Health Conditions

Takeaway: High-certainty evidence remains lacking for some anti-inflammatory dietary patterns and some chronic conditions. However, adherence to diets such as the Dietary Approaches to Stop Hypertension (DASH) and Mediterranean eating patterns might have beneficial associations with reduction or management of chronic disease risks associated with blood pressure, liver diseases, cognitive function, and some types of cancer. Moreover, adverse events or harms associated with these diets are essentially non-existent.

Six of 10 adults in the United States have at least one chronic health condition such as heart disease, cancer, diabetes, dementia, osteoarthritis, or an autoimmune disorder. Some evidence suggests that inflammation contributes to these conditions, and other lines of evidence support particular dietary patterns to reduce risk for some of these conditions.

In response to a request from VA’s Clinical Nutrition Committee, HSR’s Evidence Synthesis Program (ESP) Center in Los Angeles, CA, conducted a systematic review of reviews on the evidence of the potential roles of anti-inflammatory dietary patterns — including the Dietary Approaches to Stop Hypertension (DASH) diet, Mediterranean diet, the Dietary Inflammatory Index (DII), vegetarian/plant-based and vegan diets, and other anti-inflammatory diets — in the prevention and management of chronic conditions where anti-inflammatory diet and related interventions are not yet established as one standard of care. The review did not seek to recommend any specific dietary pattern, and did not include studies on diabetes, obesity, or cardiovascular disease. The ESP team searched for relevant articles from inception to July 2023 in MEDLINE, CINAHL, Cochrane Database of Systematic Reviews, Canadian Agency for Drugs and Technologies in Health, National Center for Biotechnology Information Bookshelf, and VA Dimensions, and in PROSPERO for reviews in development. A total of 28 studies were included in the review.

Summary of Findings

• Proposed impacts of anti-inflammatory dietary patterns on — or associations of these dietary patterns with — risks for some chronic diseases and mortality lack a strong evidence base.
• Although multiple anti-inflammatory dietary patterns, including the DASH diet, Mediterranean diet, and to a lesser extent, vegetarian/plant-based diets, appear to be associated with lower risks for some chronic conditions — including hypertension, some types of cancer, and liver diseases — these observations could be due to foods excluded from these dietary patterns, foods they include, or both.
• Despite the lack of a full understanding of how anti-inflammatory diets might help prevent and manage some chronic conditions, the demonstrated benefits for other conditions and apparent lack of harms suggest that there may be no downside to adopting one of these diets.

Conclusions supported by high certainty of evidence

• The DASH diet was associated with significant reductions in systolic and diastolic blood pressure compared with the consumption of other diets and might be the most effective dietary measure to reduce blood pressure among individuals with hypertension or pre-hypertension.
• A five-point increase in adherence to the DASH diet reduced cancer-related mortality by 3% and reduced the risk for all-cause mortality by 5%.
• Better adherence to a Mediterranean diet was associated with decreased risk of frailty and pre-frailty.

Conclusions supported by moderate certainty of evidence

• Observational studies found associations of the Mediterranean Diet, DASH diet, and lower DII scores with reductions in various cancer risk outcomes.
• Adherence to the Mediterranean diet and the DASH diet and lower DII scores is associated with lower risks for cirrhosis and nonalcoholic fatty liver disease.
• Adherence to the Mediterranean diet is associated with reduced risk for cognitive decline.

Implications

Adherence to diets such as DASH and Mediterranean eating patterns might have beneficial associations with reduction or management of chronic disease risks associated with blood pressure, liver diseases, cognitive function, and some types of cancer. Moreover, adverse events or harms associated with these diets are essentially non-existent. It is important to note that these dietary patterns and the DII all include an emphasis on a variety of vegetables, legumes, fruits, nuts, less-processed grains, and minimal intake of saturated fat, red meat, and full-fat dairy products.

Limitations

Most studies aimed at assessing the role of dietary patterns or individual foods or nutrients on chronic disease endpoints are relatively low-quality observational studies that rely on self-report or other potentially inaccurate methods of assessing exposures and adherence and on measures of intermediate outcomes of unclear value. In addition, the ESP team selected only the most recent or most inclusive reviews for this map and might have missed reviews that arrived at different conclusions.

Future Research

Intermediate outcomes such as biomarkers that have consistent, significant associations (positive or negative) with disease risk must be identified and ideally, some chain of causality must be established. The idea that a dietary pattern that non-selectively suppresses inflammation might have health benefits needs extensive clarification. Then it will be necessary to determine whether certain combinations of foods or nutrients or certain overall dietary patterns or the avoidance of certain foods or eating patterns are responsible for the observed health outcomes and whether these outcomes are also affected by other modifiable lifestyle characteristics.

Newberry S, Chen D, Shekelle P, Mak S, Begashaw M, De Vries G, Miake-Lye I. Beyond Diabetes, Obesity, and Cardiovascular Disease: An Evidence Map of Anti-Inflammatory Diet and Related Dietary Interventions for the Prevention and Management of Chronic Health Conditions. Washington, DC: Evidence Synthesis Program, Health Systems Research, Office of Research and Development, Department of Veterans Affairs. VA ESP Project #05-226; 2024.

To view the full report, go to https://www.hsrd.research.va.gov/publications/esp/anti-inflammatory-diet.cfm.

How can VA leadership work with the ESP? Nominations for systematic review topics may be submitted to the program at any time. When you submit a topic nomination form, ESP Coordinating Center staff will work with you to determine the appropriate research approach and ESP product to address your questions of interest. Topics are selected and assigned to an ESP Center based on program capacity and alignment with VA national goals

This Management Brief is provided to inform you about recent HSR findings that may be of interest. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs. If you have any questions or comments about this Brief, please email CIDER. The Center for Information Dissemination and Education Resources (CIDER) is a VA HSR Resource Center charged with disseminating important HSR findings and information to policy makers, managers, clinicians, and researchers working to improve the health and care of Veterans.

This report is a product of VA/HSR's Evidence Synthesis Program (ESP), which was established to provide timely and accurate synthesis of targeted healthcare topics of particular importance to VA managers and policymakers; and to disseminate these reports throughout VA.

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