Newsletter from DARCOF | January 2008

New research on organic food, metabolites and health

By Charlotte Lauridsen, University of Aarhus, and Søren Husted, University of Copenhagen, Denmark



The DARCOF project OrgTrace sets out to study the impact of different agricultural management practises on the ability of crops to assimilate trace elements from the soil and to synthesise bioactive compounds with health promoting effects. Also, the project will extend previous observations, using rats as model animals, that have indicated significant effects of diets on health aspects that have rarely been assessed, e.g., immune status, sleep/activity pattern, and vitamin E status.

Trace elements, bioactive secondary metabolites and vitamins are among the most important quality parameters in plants. Yet, very little information is available on their content, bioavailability and health effects in organically grown plant food products.

The new DARCOF project OrgTrace sets out to study the impact of different agricultural management practises on the ability of cereal and vegetable crops to assimilate trace elements from the soil and to synthesise bioactive compounds with health promoting effects.

The agricultural pratices will be applied in three different geographical locations, which enables us to verify if a number of common organic plant products contain a unique chemical fingerprint, differing significantly from similar conventional plant products

The field experiments will be implemented together with state-of-the-art analytical and statistical techniques allowing solid conclusions to be drawn on the variability and optimum levels of bioactive compounds such as molecular species of the elements iron (Fe), zinc (Zn), selenium (Se), sulphur (S) and health promoting bioactive metabolites (flavonoids and carotenoids), antioxidant vitamins (vitamin C and E) and phytates.

Also, the relationship between human bioavailability of the nutrients studied and will be studied in intervention studies using diets composed of the plant products produced in other DARCOF projects 'CROPSYS' (see below) and 'VEG-QURE'.

The first data from OrgTrace are expected to be available during months of spring 2008.

Health studies with rats as model animals

Observations from a recently published study (Lauridsen et al., 2007) concluded that differences between dietary treatments composed of ingredients from different cultivation methods caused differences in some health-related biomarkers, which, in future studies, should be assessed with respect to health implications. The study used rats as model animals, and the results will be further explored in OrgTrace.

The primary results were previously reported in DARCOFenews, March 2005 (see Box 1). Yet, the study, like most other studies reported in the literature, suffered from the fact that only one replication per food produce was used in the animal studies, whereby the variation due to sources like field and seasonal variations, respectively, could not be estimated.

The systematic approach of OrgTrace, with genuine replications of the food production systems, will be a major improvement compared to previous studies, where organic and conventional foods have been compared on the basis of a relatively narrow selection of compounds with limited information about agricultural practice and growth history.

Thus, the OrgTrace project collaborates with another large DARCOF project CROPSYS that includes a long-term organic crop rotation experiment (initiated in 1997) at three different locations in Denmark. In 2005 this croprotation experiment was modified to include also a conventional system. This experiment includes three 4-year crop rotations representing an organic green manure/cash crop rotation, an organic cash crop rotation and a conventional cash crop rotation. Produce from these well-controlled crop rotations will be used for preparing the diets to be tested in the OrgTrace project.

Reference

Lauridsen, C.; Chen Yong, Ulrich Halekoh, Susanne Højbjerg Bügel, Kirsten Brandt, Lars Porskjær Christensen, and Henry Jørgensen (2007). Rats show differences in some biomarkers of health when eating diets based on ingredients produced with three different cultivation strategies. Journal of the Science of Food and Agriculture 2007.








Box 1: Outline of previous study



In a previous study conducted under 'DARCOF II' it was investigated, through a well controlled animal feeding experiment, whether conventional and organic food products showed differences in animal physiology of a type and magnitude that indicate whether organic products would affect humans differently.

Effects on rarely assessed health aspects

In one of the sub-projects (Lauridsen et al., 2007), a rat-feeding experiment was performed comparing the effect of three iso-energetic and iso-nitrogeneos diets composed of vegetables (potatoes, carrots, peas, green kale, apples) and a high content (13%) of rapeseed oil, produced according to each of three cultivation systems on a range of physiological responses (utilisation of nutrients, immunity, antioxidative defence, and health status).

Even though the dietary treatments were similar in terms of nutritional quality, some notable differences appeared with regard to some of the measured biomarkers (concentration of vitamin E and immunoglobulin, daytime activity, volume of adipose tissue, liver metabolic function, and liver lipid peroxidation) that have until now not been assayed in similar comparative studies. In contrast, a large numbers of markers of 'traditional' nutrient value showed no differences. The results of the study could not be applied to organic and conventional production systems because the production systems used in this study was not replicated and represented combinations of relevant methods rather than actual commercial systems. However, it could be concluded from the study that in future studies, designed to take the variability of cultivation systems used for conventional and organic growing into consideration, focus should be directed on these health biomarkers.