Many consumers expect organic food to be healthier than food produced under conventional conditions. But scientifically there is a lack of investigations that could support this view. For one reason, it is difficult to test the influence of foods on heath, because a range of other parameters also influences health.
The scientists found that the organically fed rats enjoyed several health benefits, in that they slept better, had stronger immune systems and were slimmer than rats fed conventional diets.
Similar tests would need to be carried out on humans to determine if organic food would have the same effect on them.
Diets from three cultivation strategies
The experiment was done with 36 rats that were fed on three diets consisting of potatoes, carrots, peas, green kale, apples, and rapeseed oil. The difference between the three diets was that the ingredients were grown according to three different cultivation strategies:
- Organically: with low input of fertilizer and without pesticides
- Minimally fertilized: with low input of fertilizer and with pesticides
- Conventionally: with high input of fertilizer and with persticides
The diets had similar energy and protein contents, and had a relatively high content of fat as compared to the recommended level for rats. The diets were analysed for pesticide residues, but these were below detection limits in all three diets.
Vitamins, minerals and amino acids were added to all three diets to fulfil the rats' requirements. The rats received the same diets throughout their life and the measurements of heath started after weaning of their first litter (age, 19 weeks; weight, 212 g).
Measurement of health
The health of the rats was examined through physiological response measurements that comprised nutrient utilisation, function of organs and physical activity. Post mortem blood and tissue samples were collected for analysis of biomarkers of health such as immune function, antioxidant status and nutritional status.
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In addition to the presently reported results, the main project comprised a range of other issues related to reproduction of the rats, bioavailability of the nutrients in the ingredients of diets, and annual variation in the content of nutrients and secondary metabolites in the ingredients.
Improved immune status
Immune status of the rats was measured as the total content of immunoglobulins in the blood serum. The results showed that rats fed on organic and minimally fertilised diets had a higher content of immunoglobulin G (IgG) than rats fed on the conventionally grown diet.
At present, we have no explanation of the lower content of IgG in the rats that were offered the conventionally grown diet. Yet, it is noteworthy that the conventional diet had a higher content of the secondary metabolite falcarindiol than the other diets. It cannot be excluded that falcarindiol may have an inhibitory effect on initiation of the immune response.
Tendencies towards less adipose tissue and better rest
The rats thrived on all three diets and only showed minor differences with respect to utilisation of energy and nutrients. Even though the rats were genetically disposed for diabetes, there was no visual sign of this disease among the rats.
The rats had only a slight increase in weight after eating the diets for 25 weeks. However, the data showed a tendency towards a lower weight and a lower content of adipose tissue in the rats that were fed on the organic diet as compared to the other diets.
Concurrently with the measurements of energy utilisation, we measured the physical activity of the rats using infrared sensors. Rats are active at night, and there were no differences between the dietary groups with respect to activity at night. However, during daytime, when the rats are supposed to rest, our data indicated that rats fed on the organic diet was more relaxed than rats feed on the other diets.
Rapeseed oil comprised 25 pct. of the energy content of the diets. Due to experimental problems there was a different composition of fatty acids and a lower vitamin E content in the rapeseed oil from the minimally fertilised treatment. This caused some differences in the fatty acid composition of the serum and the tissue of the three dietary groups of rats. Also, the vitamin E content was lower in blood plasma from rats that received the minimally fertilised diet.
The content of vitamin E in the organic and the conventional diet was similar. Yet, there was a higher content of vitamin E in the blood of the rats that were fed with the organically grown diet.
The Bottom Line
Speaking to The Journal newspaper, Dr Kirsten Brandt of Newcastle University's School of Agriculture, Food and Rural Development, who helped design the experiment said: "What this research shows is that clearly there are links between food and health which is more to do than with just nutrients. "We used to think that as long as food had adequate nutrients then it was all equally good.
"What this work has shown is that this is not the whole story and we can measure differences and that they are significant. Now we need to understand what is going on. If people think that eating organic food makes them feel better then they are probably right."
Tips on eating organic can be found in
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