Dangour, A.D., Hawkesworth, S., Shankar, B., Watson, L., Srinivasan, C.S., Morgan, E.H., Haddad, L., and Waage, J. (2013) Can nutrition be promoted through agriculture-led food price policies? A systematic review. BMJ Open, 3:e002937.Link to Source
Headline Findings: a summary statement
Few studies have investigated the impact of agricultural-price policies on nutrition and health. The limited evidence base found by this review provides some support for the assertion that agricultural policies that directly affect national food prices can affect population-level nutrition and health outcomes.
The authors identified four studies that met inclusion criteria: An ex-post study in India on the effect of reduced food subsidies on children’s nutritional status; an ex-post study in Egypt on the effect of a food-subsidy programme on the body-mass index of mothers; an ex-ante study in the Netherlands on the effect of ending a policy that withdrew fruit and vegetable produce from the market in order to keep producer prices high; and an ex-ante study in the United States on the effect that removing farm subsidies on grain commodities would have on adult weight.
Implications for policy and practice
The authors did not find any evidence that agricultural policies that directly influence the price of food, affect rates of under-nutrition. The studies that evaluated the effects of such policies on over-nutrition found a small effect on adult weight and risk of nutrition-related chronic disease.
Implications for further research
The main finding of this study is to highlight the lack of evidence in this area. As a result, the authors urge increased attention to be paid to high-quality impact evaluation of agricultural policies. They emphasise the value of using research methods from health and development, and the need for rigorous research with credible counterfactuals. They acknowledge the challenges associated with designing evaluations of the impact of agricultural policies on the nutrition status of individuals. Such challenges include lag effects due to the time required for behaviour change, the numerous external factors that affect nutrition outcomes, and the long causal chain that links agricultural policies with nutrition outcomes.
The quantity and quality of available food greatly affects the health of a country’s population. Many countries, particularly low- and middle-income countries (L&MICs), need policies to address both under-nutrition (insufficient energy intake or insufficient vitamins and minerals) and over-nutrition (obesity and nutrition-related chronic diseases such as cancer and heart disease). Agricultural policies have the potential to influence food prices, which are often closely related to quantity and quality of food consumption and thus to nutrition and health outcomes. The authors reference the growing interest in agricultural-market policy interventions. These include output-price policies (these affect the price producers are paid, such as taxes or commodity market interventions), trade liberalisation (policies that affect the prices and quantities of food imports and exports), and food subsidies and public distribution systems (policies that influence the prices that consumers pay for food, including food stamps and food-for-work programmes). To date, no previous systematic review had assessed the evidence on the link between food price policies and nutrition and health outcomes.
To review the global evidence on whether agricultural policies that directly affect the price of food affect the prevalence rates of under-nutrition or nutrition-related chronic disease in children and adults.
The authors included studies that undertook multivariate quantitative analysis evaluating or simulating the effect of national or international agricultural policies, and which could directly affect the price of food. These included output-price policies, trade-liberalisation policies or public distribution policies in any population worldwide. Primary outcomes of interest were child and adult under-nutrition rates (wasting, stunting or underweight), clinical signs of vitamin and mineral deficiency, child and adult over-nutrition rates (overweight and obesity), and rates of nutrition-related chronic disease, including cardiovascular disease, diabetes and cancer. The authors included published and unpublished studies in English that reported data collected after 1990.
The search strategy covered five databases: MEDLINE, EconLit, Agricola, AgEcon Search and Scopus. The authors also searched Eldis, the websites of relevant organisations (such as the United Nations Food and Agriculture Organisation and the World Bank) and hand-searched the reference lists of included publications. Two authors independently screened studies for inclusion, and independently extracted data from included studies. Statistical meta-analysis was not appropriate due to the heterogeneity of the included studies, so the authors presented a narrative summary.
The authors used appropriate methodologies to reduce bias in the identification and selection of studies, including clear inclusion and exclusion criteria, searching multiple databases, independent double screening and data extraction, and narrative synthesis in light of obvious heterogeneity of included studies. However, there are some major limitations with the review: The authors only included studies in English. Studies were not adequately assessed for risk of bias and the authors do not report the outcomes of their quality assessment. The authors do however acknowledge some of these limitations and call for more rigorous research in the field of agriculture-led food price policies.