A report says to take into account such factors as the environment, human health and society.

WASHINGTON — Decisions affecting one part of the food system may have unexpected consequences affecting other sectors, including the environment, human health and society. For example, if Americans doubled the amount of fish they ate to meet recommendations in the Dietary Guidelines for Americans 2010, it could lead to overfishing and depletion of wild fish stocks.

Assessments designed to bring about food system changes thus should consider positive and negative outcomes along the full supply chain, according to a report issued in January by the Institute of Medicine and the National Research Council of the National Academies. A committee developed “A Framework for Assessing Effects of the Food System.” It presents principles and steps to help stakeholders weigh tradeoffs and choose policies that integrate benefits and risks across various domains.

Farmers, processors, policy makers and consumers all make decisions that shape the food system every day, according to the report. They have diverse goals such as improving health, protecting the environment and increasing productivity.

“The committee concludes that engaging a wide variety of stakeholders throughout the assessment can promote the sharing of data and best practices, avoid conflicts of interest, ensure equitable participation and address public concerns about transparency,” the report said.

The committee considered such food and agricultural decision areas as the use of antibiotics in agriculture, recommendations for fish consumption and health, biofuel blending in gasoline supplies, recommendations to increase fruit and vegetable consumption, nitrogen dynamics and management in agro-ecosystems, and egg production practices.

“Each of these examples yields unintended consequences in multiple domains, demonstrating the complexity of the food system and the need for a framework that considers the breadth of the effects and their interactions,” the report said.

For the fish example, Americans doubling their consumption also might have a positive effect, creating new jobs in fish production and processing.

The JPB Foundation, New York, sponsored the report.