Authors' objectives:

This authoritative, systematic review seeks to clarify the existing knowledge base on interventions to alter dietary behavior related to cancer risk and offers directions for future research. Specifically, the review addresses three key questions regarding the efficacy of behavioral interventions for promoting dietary change: - Is there evidence that one such intervention, alone or in combination, is more effective than another in helping individuals or groups modify their diet to consume more fruits and vegetables and less fat? - What is the evidence for the efficacy of dietary interventions by population subgroup, particularly by ethnicity and gender? - What conclusions (if any) can be reached about the cost-effectiveness of these types of interventions?

Authors' results and conclusions: In the studies that were reviewed, dietary interventions were consistently associated with an increase in fruit and vegetable consumption (with greater increases noted for fruit intake). More than three-quarters of the studies reviewed reported statistically significant increases in fruit and vegetable intake (as a combined variable). Using the differences-in-deltas approach, the reviewers determined that the average increase in fruit and vegetable intake reported was 0.6 servings per day, and consistent decreases were noted in the intake of total fat and saturated fat. The mean change in total fat intake was estimated as a 7.3 percent reduction in the percentage of calories from fat. Interventions appeared to be more successful at positively changing dietary behavior in populations at risk of (or diagnosed with) disease than in healthy populations. Several dietary intervention components appear to be particularly promising in modifying dietary change favorable to cancer risk reduction: social support, goal setting, small groups, food-related activities, and the incorporation of family components.

Authors' recommendations: The dissimilarity across studies in terms of outcome measures, study design, analysis strategy, and intervention technique makes it difficult to draw broad conclusions about the efficacy or effectiveness of behavioral dietary interventions. For example, investigators tended to employ more intensive interventions with high-risk populations, making it difficult to discern whether population or intervention characteristics were primarily responsible for increased change in dietary behavior. However, some intervention components may hold promise for future research efforts. Very few studies were appropriately designed or reported to allow interpretation of evidence for the efficacy of the interventions by population subgroup, particularly low-income or ethnic subgroups. Despite increased Federal agency funding for dietary intervention research in underserved and minority populations, a serious deficit still exists in good-quality, published research designed to determine the relative efficacy of different intervention approaches in these groups. Furthermore, few studies followed participants for more than a year, and those that did often showed a falling off in the initial dietary behavior change achieved. Thus, more research is needed to determine the longer-term effectiveness of dietary interventions in both the general population and important subgroups and to evaluate programs specifically designed to prevent relapse over time. Finally, no studies that met the review criteria provided data on the cost-effectiveness of dietary interventions. Comparing the cost-effectiveness of current and innovative intervention approaches will be critical to assessing their broader applicability.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/dietsumm.htm

Year Published: 2001

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)