Agroecosystem Management and Nutritional Quality of Plant Foods: The Case of Organic Fruits and Vegetables

Abstract

Organic and conventional crop management systems differ in terms of the fertilisers and plant protection methods used. Ecological and agronomic research on the effect of fertilization on plant composition shows that increasing availability of plant available nitrogen reduces the accumulation of defense-related secondary metabolites and vitamin C, while the contents of secondary metabolites such as carotenes that are not involved in defense against diseases and pests may increase. In relation to human health, increased intake of fruits and vegetables is linked to reduced risk of cancer and cardiovascular disease. This benefit may be primarily due to their content of defense-related secondary metabolites, since most other constituents of fruits and vegetables either are not unique to these foods or have been shown to not provide health benefits when the intake is increased. A meta-analysis of the published comparisons of the content of secondary metabolites and vitamins in organically and conventionally produced fruits and vegetables showed that in organic produce the content of secondary metabolites is 12% higher than in corresponding conventional samples ( P< 0.0001). This overall difference spans a large variation among sub-groups of secondary metabolites, from a 16% higher content for defence-related compounds ( P< 0.0001) to a nonsignificant 2% lower content for carotenoids, while vitamin C showed a 6% higher content ( P= 0.006). Based on the assumption that increasing the content of biologically active compounds in fruits and vegetables by 12% would be equivalent to increasing the intake of fruits and vegetables by the same 12%, a model developed to calculate the health outcome of increasing the intake of fruits and vegetables was then used to tentatively estimate the potential increase in life expectancy that would be achieved by switching from conventional to organic produce without changing the amount consumed per day, to 17 days for women and 25 days for men.

Keywords:

• Organic food
• secondary metabolites
• plant defense compounds
• health benefits
• meta-analysis

ACKNOWLEDGMENTS

K. Brandt gratefully acknowledges funding in 2007 from the Food and Agriculture Organization of the United Nations (FAO), Rome ($10,000) and the Soil Association, Bristol (£1,000) for review reports that contributed to the basis of the present review.

C. Leifert gratefully acknowledges funding from the European Community under the Sixth Framework Programme for Research, Technological Development and Demonstration Activities, for the Integrated Project QUALITYLOWINPUTFOOD, FP6-FOOD-CT-2003-506358, for the proteomics work.

The authors wish to thank Prof. M. Petticrew, London School of Hygiene and Tropical Medicine, for helpful comments on a draft of the manuscript, and Miss D. Srednicka for assistance with proofreading of the data.

Support is also gratefully acknowledged from The Sheepdrove Trust for the recently commenced project ‘Meta-analysis of data on composition of organic and conventional foods’ (MADOC), which hosts the website where the dataset used in the present analysis is deposited.

Referee: Prof. Denis Lairon, INRA, UMR 1260, Nutriments Lipidiques et Prévention des Maladies Métaboliques, U476, Univ. Aix-Marseille, Faculté de Médecine, 13385 Marseille, France.