Cambridge scientists may have discovered a new way in which fasting helps reduce inflammation – a potentially damaging side-effect of the body’s immune system that underlies a number of chronic diseases such as Alzheimer’s and Parkinson’s. Fasting raises levels of a chemical in the blood known as arachidonic acid, which inhibits inflammation. Fasting can help reduce inflammation, but the reason why has not been clear. The team found that restricting calorie intake increased levels of a lipid known as arachidonic acid. This came as a surprise as arachidonic acid was previously thought to be linked with increased levels of inflammation, not decreased.