A varied diet keeps the immune system alert, but it doesn't matter whether the feed was grown organically or in the usual manner. Variation in the diet means variation in mild stress.
It seems obvious: each individual reacts differently to stress, for example to changes in the living or working environment. As Adriaansen says to illustrate the personal nature of stress: what one individual experiences as stress has no effect at all on the stress system of another individual. The susceptibility to stress directly affects the immune system's response, and through this one's health.
Diet also affects an individual's stress response. Adriaansen based her findings on research into chickens carried out as part of a large-scale study of the potential health benefits of organic feed. The study used leghorn hens that had been given the same feed for 25 generations on the run. One group of these hens was fed organic chicken feed and another group was given similar chicken feed, but grown in the standard way.
The groups were followed for two generations, using analyses of their blood, for instance. The study showed that the immune systems of all the groups responded more alertly. Adriaansen: 'The change in feed gives the immune system a jolt. This doesn't just change the resistance to sickness, it also affects the hormonal system and as a result the susceptibility to stress. Whether the feed was grown organically or produced in the usual manner has no affect on this mechanism. We cannot say which diet is best.'
Does this mean there is still no conclusion to the long-running debate on whether or not organically grown food is healthier? 'That's right', says Ruth Adriaansen. 'This study shows that it is all much more complicated. Each individual reacts to stress - and therefore to food - differently. You can't predict what will happen. The study has raised many new research questions. As science advances, so does our understanding.'