The time of day that we take a medicine could have a dramatic impact on its potency, new research suggests.
A British study has determined for the first time how the chemistry of our blood stream changes throughout the day.
Scientists at the University of Surrey and the Institute of Cancer Research in London have shown that the body clock has a profound role in altering the concentration of different molecules in our blood.
The finding means that the amount of sleep we have had, the levels of light to which we are exposed and the timing of our meals could all alter on the way drugs work on our body.
It also suggests that blood tests for diseases may produce different results depending on the time of day.
Nearly all living things have an internal mechanism – known as the circadian rhythm or body clock – which synchronises bodily functions to the 24-hour pattern of the Earth’s rotation.
In humans and other mammals, the clock is regulated by the bodily senses, most importantly the way the eye perceives light and dark and the way skin feels temperature changes.
The mechanism rules our daily rhythms, including our sleep and waking patterns.
The new study, published in the journal the Proceedings of the National Academy of Sciences, is the first to establish the way the body clock also affects our metabolism.
Professor Debra Skene from the University of Surrey, said: ‘Our results show that if we want to develop a diagnostic test for a disease, it is imperative to take the time of day when taking blood samples into account, since this has a significant effect on metabolism.
‘This is also key for administering medicines and determining when they will be at their most effective.
Of course, this will have to be considered on a case-by-case basis, since many people such as shift workers will have a different sleep/wake cycle and timings will need to be adapted to their body clocks.’
She said more research is needed on which drugs are particularly effected, but previous work has shown that the efficacy of certain treatments for diabetes, cancer and liver cirrhosis are altered by the time they are administered.
Professor Skene added: ‘There is good evidence – for example in chemotherapy – that administering drugs at an optimal time increases its effectiveness and reduces the incidence of side effects.’
The metabolism of a group of healthy male volunteers was tracked for 48 hours as their access to light, sleep and meals was controlled.
For the first 24 hours, the volunteers were put through a normal wake-sleep cycle.
This was followed by 24 hours when they were deprived of all sleep.
The researchers found that 27 different chemicals in the blood were found at higher levels while the men were sleep deprived.
Dr Florence Raynaud, who co-authored the paper, said: ‘Our findings are likely to be important in interpreting the results of blood tests, and in understanding why some individuals respond differently to medication.
‘They also set reference points for future studies looking at the connection between metabolic processes and diseases such as cancer.’
