Food Entrainment of the Human Circadian Timing System

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Most living organisms possess internal clocks that regulate daily (circadian) rhythms in many key biological functions (e.g. hormone secretion, sleep time, metabolism). The circadian timing system in mammals, including humans, consists of a 'master' clock within a part of the brain called the hypothalamus and many 'peripheral' clocks found throughout the body. There is increasing evidence to show that abnormal timing of these clocks leads to defects in normal biology. The effects of this abnormal timing can be short lived (e.g. in jet lag) or present over a number of years (e.g. in shift workers). In the second scenario, the long term effects of abnormal rhythms is thought to be a causative factor in many industrial accidents and can lead to increased incidence of major contributors to ill health, such as heart and metabolic diseases. In order for our internal clocks to be matched to external changes in the environment, they are synchronised by various environmental time cues. Although it is known that light is the main synchroniser of the 'master' clock in the brain, the synchronisation of peripheral clocks is poorly understood. Evidence from animal studies suggests that the time of feeding is an important signal for peripheral clocks. However, these animal experiments have not been performed in humans because; 1) very few places in the world can perform well controlled human circadian experiments, and 2) it is difficult to obtain multiple samples of human tissue other than blood. At the University of Surrey, we have the benefit of excellent human biology facilities, experts in circadian rhythms, and experts in nutritional science. Moreover, in our recent research, we have optimised a method for taking multiple samples of fat from human volunteers. We therefore propose to conduct a set of extremely important and timely experiments to discover whether the time of feeding can regulate human clocks. The results of the work will have important implications for scientists and the public. Scientists will learn crucial new information about the basic biology of body clocks. If food is found to be able to regulate circadian timing then this would identify novel treatment strategies that may lead to novel dietary interventions to reduce the burden of shift work and jet lag on health and performance. There has been a lot of public and media interest in both body clocks and nutrition over recent years and so this research is likely to be of broad interest. In particular, we hope to discover new scientific findings that will underpin non-drug treatment for sufferers of circadian disorders including air travellers, shift workers and the totally blind.