Our body's glucose tolerance varies depending on the time of day, a study by Harvard researchers has confirmed. As it turns out, it is not only what we eat that matters, but also when we eat. Indeed, glucose tolerance is reduced in the evening and much better in the morning. Disregarding this characteristic of the body can be fatal and lead to diabetes, which is particularly important in the context of workers doing shift work - disrupting the daily biological rhythm.
A team of researchers from Harvard, joining forces with specialists from Brigham and Women's Hospital, conducted a study on the influence of external factors - behavioural (such as meal timing, sleep cycle, wake-up time) - and the biological clock and possible shifts between these 2 elements on the body's ability to control blood glucose levels. This tightly-controlled study involved 14 people and went a long way towards understanding where our body's variable glucose tolerance - increased in the morning and decreased in the evening - comes from. In relation to the conclusions drawn from the study, the danger that shift work, for example, poses to humans has been noted [1].
It is not only the type of food we eat that matters, but also the time at which we eat. This can have health consequences in terms of the diurnal rhythm. The study carried out was based on 2 protocols - the first involved breakfast at 8 a.m. and sleeping through the night, while the second involved a 12-hour shift, with breakfast in the evening hours and dinner in the morning hours. What's more: the energy value of the menus was the same in both cases, and the researchers continuously monitored the subjects' glucose levels. A so-called 'diurnal shift' was observed - lack of sleep at night, as in the case of people working through the night, results in lower glucose tolerance during the following days. Glucose levels were significantly higher in those eating in the evening, which may indicate reduced glucose tolerance just at that time of day. The main risk posed by both the diurnal shift and the consumption of heavy meals in the evening is the possibility of diabetes [1].
Diabetes belongs to a group of metabolic diseases characterised by hyperglycaemia, which is a direct result of abnormalities in insulin secretion and action. If there is a chronic condition, prolonged hyperglycaemia, there is a likelihood of damage that involves disorders of various systems and organs - eyes, kidneys, nerves, heart and blood vessels.
In order to make a definite diagnosis, it is necessary to confirm the abnormalities, excluding fasting blood glucose, by taking into account the results of the 2-fold abnormality in the blood glucose determination. It is important to take into account factors that are not directly related to the test - the time of consumption of the last meal, physical exercise or the time of day precisely - when taking the test material [2].