Time-clock tells how body ticks

Press, Volume CXIV, Issue 33448, 1 February 1974, Page 14

Time-clock tells how body ticks

(By

SANDRA JOBSON)

LONDON. New research into the body’s biological timeclock has revealed surprising facts about human behaviour. For instance—did you know that you can eat more at breakfast than at any other meal—and still keep slim? Or that your sex hormones are at their peak round 7 o’clock- in the morning? Using data collected by the University of Minnesota chronobiology department and the Max Planck Institute in Germany, scientists have constructed a human time graph. The graph traces the daily behaviour of the average person, marking the ups and downs of mood, fluctuations in energy, body temperature, hormone excretion and heartbeat. Some of the information could save lives. We all have an in-built mechanism which synchronises our bodily functions. This mechanism is not basically affected by day or night, light or dark, or by our ordinary concept of time. Research on volunteers who went underground and lived in bunkers at the Max Planck Institute for months revealed unusual facts about this internal clock. The results were shown on “Horizon,” on the BBC. The volunteers were cut off from the outside world. They could hear nothing outside the bunker and had no watch or clock to tell the time.

The bunkers were cut off even from the earth’s magnetic pull. And the lights were kept on at all times. The scientists found that their “guinea pigs” functioned on an internal time-clock with a “circadian rhythm” of about 25 hours.

And although the volunteers had no idea whether its was day or night, the circadian rhythm went through a definite and regular cycle. When the experiment was over, the subjects returned to the outside world and were asked to say how long they thought they had been under-, ground. Almost all miscalculated the time by up to a week and more.

They had been functioning on what is called “free running time.” After a few days above ground they reverted to a 24-hour body rhythm geared to the rising and' setting of the sun. Basic time-table Using these data and comparing them with observations of people in ordinary life, the researchers compiled this basic time-table: 6 a.m. to 7 a.m.: Just before you wake, your adrenal glands start pumping out extra adrenalin. Sex hormones are at their peak. Blood clotting is low. 8 a.m.: You can eat food without converting it to fat. 10 a.m.: You are unable to work efficiently. Sight and smell functions are low. Midday: You have a postlunch dip in behaviour. Even if you don’t eat lunch, this dip still occurs. It is particularly severe, however, if you drink alcohol. The effect of

alcohol is more powerful at this time of day. 4 p.m.: Your mental efficiency is at a peak. 6 p.m.: Physically you are at your best. Blood pressure rises. You are more aggressive.

8 p.m.: Both your mental and physical powers are in harmony and functioning well. Your body weight is at its heaviest for the day. 3 a.m.: Hormones, temperature, heart-beat are at their lowest ebb. Cells divide to regenerate your skin. Your hearing is at its sharpest. Two types The scientists agree, however, that people can be divided into “morning” and “evening” types. Morning people, who function best before midday are usually introverts. Evening people are more extroverted. But the researchers found that nobody, even people who are accustomed to it, work as efficiently at night as in the day. And people who work shifts are worse off than people who always work at night, because their timeclocks never adjust. This could have serious consequences for pilots, doctors, nurses and night drivers, who are particularly vulnerable to the drop in efficiency which could endanger the lives of others. Ten times as many planes crash at night, and most road crashes and deaths on the operating table occur around 4 a.m., when the body is at its lowest point. More babies are born at night than in the day. The peak time for the onset of labour is 1 a.m. and the peak time for birth is 4.16 a.m. A serious consequence of our fixed time clocks is that humans, like animals, respond differently to drugs at various times of the day and night. This means that a dose regarded as “normal” could be too much if administered at an adverse time. Experiments on mice have shown that similar dosages of a drug can affect mice in dramatically different wavs according to the time, ranging from drowsiness to death. Danger signs Ihe research is convincing scientists that we may well have more than one internal clock. Each clock monitors the function of one of the body’s organs, such as the heart. Children at a Minnesota high school are being taught to check their own body time clocks. They are given a testing kit which includes a bloodpressure gauge, a stop-watch to time the pulse, and a thermometer. They are learning to watch for danger signals in their own bodies which indicate that their internal clocks are out of synchronisation. The scientists believe that if everybody could be taught to monitor himself many illnesses could be diagnosed early or even prevented. They say that good health may simply be the result of all the internal clocks being synchronised and working together in harmony. Stress in the body rhythm is regarded as the killer.