Organic foods are a hit with some consumers. An important driver for this organic consumption is the consumer's perception of the products having a series of positive effects. Some consumers eat organic food because they feel that it has a positive effect upon their health.

Is this just a belief – or can this opinion be supported by scientific facts? Do organic cultivation systems affect the nutritional quality of crops? Does one become healthier by eating organic – and how does one measure it?

- Research results surrounding organic foods are very divergent, and there has been a lack of research concerning the influence on animal and human health, says PhD research fellow Maya Melballe Jensen from Aarhus University. She has compared the effect of organically versus conventionally grown crops on a series of health parameters in rats and found that the effect upon the measured health parameters was minimal.

Variables in the crops
There are several factors that might come into play in an investigation into crops and their effects upon health. As a result, it was decided to follow the food chain from farm to fork and follow the effect upon rats over a long period of the rats' life.

Another variable in the comprehensive studies was whether the crops had been fertilised by livestock manure or artificial fertiliser or had been grown in a crop rotation with catch crops.

The crops for the experiment were grown either organically or conventionally, and the experiment was set up so that comparisons could also be made between harvest year and cultivation locality. Thus, factors such as weather and soil type were also addressed, but by other partners in the large, interdisciplinary research collaboration..

In the different experiments there was a difference in the menus, in that the rats in one experiment were given carrots as a supplement to their usual feed while the menu in the two other experiments were complete diets consisting of potatoes, rapeseed oil, wheat, barley and fava  beans.

There was thus a wide selection of feed types lined up to be tested on the rats to see whether organic derivation, year, locality, fertilisation and crop type affected the health of the animals.

Rat health
The next thing was to investigate the health effects on the rats. In order to measure the concept of  ”health” it was decided that the immune status of both the mothers and their young was to be measured. Beyond this, their antioxidant status, fatty acid profiles and physical activity were all registered as indicators of their health.

- The definition of health and the potential biological indicators of health are under heavy debate. One of the aspects is that the immune system can be modulated by nutrients and that the immune system is affected during the foetal stages and early life, explains Maja Melballe Jensen.

If the rats have a good immune response, they will be good at creating antibodies against foreign, potentially dangerous substances (antigens). One of the aspects of the immune system is, however, also whether or not the animal is capable of tolerating harmless antigens. If it is not, it will develop an allergic condition.

In one of the tests it was evaluated whether feeding the mother rat organic crops during pregnancy and lactation could affect the young rat’s tolerance to a harmless antigen. Egg white was used as a harmless antigen, which was added to the drinking water of the mother rats during the lactation period, and was thus passed via the milk to the young.

No improvement in immune status
The overarching conclusion of the long series of experiments was that organically cultivated crops do not affect the immune status of the rats to any significant degree.

- One should, however, be aware that the results from the experiments in question cannot be translated directly to humans due to physiological and immunological differences, says Maja Melballe Jensen and continues:

- Previous individual experiments have shown higher levels of antioxidants in the blood and in diverse immunological bioindicators if you eat organic products, but what significance does this have? That you are healthier? That you live longer? This is hard to prove.

- One of the explanations to previous experiments having suggested a difference in the healthiness in favour of organic crops is that they contain fewer pesticides. These days, however, there are also fewer pesticides in conventional Danish crops than before, and the amount of fertiliser applied to crops has been reduced so there is not as much difference between conventional and organic crops as there perhaps once was.

For further information please contact: PhD Maja Melballe Jensen, Department for Animal Science, email: Maja.Jacobsen@agrsci.dk, telephone: +45 8715 4256 or main supervisor, Head of section Charlotte Lauridsen, Department of Animal Science, e-mail: charlotte.lauridsen@agrsci.dk, telephone: +45 8715 8019