Perspective: USDA Nutrition Evidence Systematic Review Methodology: Grading the Strength of Evidence in Nutrition- and Public Health–Related Systematic Reviews

Abstract

The U.S. Department of Agriculture's Nutrition Evidence Systematic Review (NESR) team conducts food- and nutrition-related systematic reviews used to inform U.S. Federal guidelines and programs, including the Dietary Guidelines for Americans. NESR's systematic review methodology includes a step to grade the strength of the evidence underlying conclusion statements, which is critical for ensuring that end users understand the level of certainty in conclusions when using them to make decisions. Over time, NESR has ensured its grading process not only remains state of the art but is also designed specifically for systematic reviews that inform Federal guidelines and programs on nutrition and public health. The NESR grading process used by the 2020 Dietary Guidelines Advisory Committee included five grading elements: risk of bias, consistency, directness, precision, and generalizability. Evidence was grouped by study design and assessed against these elements, and the grade assigned to the entire body of evidence took into consideration the strengths and limitations of each design. Based on this assessment, one of four grades was assigned: strong, moderate, limited, or grade not assignable. The grade was clearly communicated by integrating language into each conclusion statement (e.g., “strong evidence demonstrates” or “limited evidence suggests”), and supported by rationale documented in the review. NESR's grading process aligns with approaches used by other organizations that conduct systematic reviews, while retaining aspects unique to NESR's role in informing Federal nutrition and public health guidelines and programs. It provides a framework that promotes consistency in grading across food and nutrition-related reviews, while offering flexibility that allows for thorough consideration of the body of evidence underlying an individual conclusion statement. NESR's rigorous and transparent methods for grading the strength of evidence in food- and nutrition-related systematic reviews ensures that decisions related to diet and public health are based on the strongest available evidence.

Perspective: Examining Conflicts of Interest for Professional Service within the 2020 Dietary Guidelines Advisory Committee

“…Details of the DGA processes are described elsewhere [ 18 , 22 , [28] , [29] , [30] , [31] ]. The 835-page DGAC 2020 scientific report [ 7 ] was shared with the USDA and HHS Secretaries for internal institutional review, and the recommendations were translated into simple messages before the agencies released the 164-page DGA 2020 to 2025 report in December 2020 [ 8 ].…”

Dietary pesticide exposure and non-communicable diseases and mortality: a systematic review of prospective studies among adults

“…We systematically reviewed prospective studies aimed at estimating the associations between dietary exposure to pesticides and NCD among adults. The methodology for conducting systematic review in nutrition and public health developed by the United States Department of Agriculture (USDA)’s Nutrition Evidence Systematic Review (NESR) team [ 13 ] was used. This systematic review was planned and conducted in accordance with the standards of PRISMA-2020 [ 14 ].…”

Evidence and suggestions for establishing vitamin D intake standards in Koreans for the prevention of chronic diseases

“…Strength of evidence assessment was evaluated using the U.S. Department of Agriculture Nutrition Evidence Library Conclusion Statement Evaluation Criteria. Based on this assessment, studies were assigned as grades 1 to 4, signifying strong, moderate, limited, or grade not assignable, respectively (e.g., “strong evidence demonstrates” or “limited evidence suggests”) [ 29 ].…”