CIRCADIAN RHYTHMS AND THE INTAKE OF FOOD. All living creatures, from the simplest bacteria to human beings, have evolved a way of coordinating their activities with the day-night cycle associated with the rotation of the Earth. These circadian rhythms govern not only our periods of waking and sleeping but also the way in which we absorb nutrition: for example during the night, when no food is being consumed, the liver synthesizes glucose and secretes it into the circulation, whereas during the day this system is silenced because sufficient quantities of sugar are provided by the diet. Download the column