Jet Lag: Prevention and Cure

　　The problem of Jet Lag is one every international traveller comes across at some time. But do you have to suffer? Understand what it is, and how a careful diet can minimize its worst effects, and your flights will be less stressful.

　　The effects of rapid travel on the body are actually far more disturbing than we realize. Jet Lag is not a psychological consequence of having to readjust to a different time zone. It is due to changes in the body's physiological regulatory mechanisms, specifically the hormonal systems, in a different environment.

　　Confused? So was John Foster Dulles, the American Secretary of State, when he flew to Egypt to conduct negotiations on the Aswan Dam.

　　He later blamed his poor judgement on Jet Lag.

　　The effects can be used to advantage, too. President Johnson once conducted an important meeting in Guam and kept the entire proceedings at Washington DC time. The White House working personnel were as fresh as paint, while the locals, in this case, were jet-lagged.

　　Essentially, they had been instantaneously transported to America.

　　Now that we understand what Jet Lag is, we can go some way to overcoming it. A great number of the body's events are scheduled to occur at a certain time of day. Naturally these have to be regulated, and there are two regulatory systems which interact.

　　One timing system comes from the evidence of our senses and stomachs, and the periodicity we experience when living in a particular time zone. The other belongs in our internal clocks (the major one of which may be physically located in a part of the brain called the suprachiasmatic nucleus) which, left alone, would tie the body to a 25 hour - yes, 25 - rhythm. Normally the two timers are in step, and the external cues tend to regularise the internal clocks to the more convenient 24 hour period.

　　If, however, you move the whole body to a time zone which is four hours different, the two clocks will be out of step, like two alarm clocks which are normally set together, but which have been reset a few hours apart. Whereas the two clocks would normally sound their alarms together, now they ring at different times. Similarly, the body can be set for evening while the sun is rising.

　　In time the physiological system will reset itself, but it does take time. One easily monitored rhythm is palm sweating. A man flown to a time zone different by 10 hours will take eight days to readjust his palm sweat. Blood pressure, which is also rhythmical, takes four days to readjust.

　　One reason for this discrepancy is that different bodily events are controlled by different factors. The hormone cortisol, which controls salt and water excretion, is made in the morning, wherever the body is. But the growth hormone is released during sleep, whenever in the day that sleep occurs. Normally these two hormones are separated by seven or eight hours, but if the body arrives at a destination in the early morning (local) and goes to sleep as soon as possible, the two hormones will be released simultaneously.

　　What can we do about it? It is not feasible to wait four days until the body is used to the new time zone. Fortunately there is a short cut. It relies on two things - the power of the stomach to regulate the timing of other events, and the pharmacological actions of coffee.

　　The basic assumptions are:

　　Coffee delays the body clock in the morning, and advances it at night. Coffee at mid-afternoon is neutral.

　　Protein in meals stimulates wakefulness, while carbohydrates promote sleep.

　　Putting food into an empty stomach helps synchronize the body clock.

　　時差綜合癥的預防和治療

　　高速飛行時因時差而引起的生理節奏的推敲是每一個跨國旅行者有時會遇到的問題。但你必須得忍受嗎?如果你了解它是怎么回事，并且知道如何注意飲食才可以將其最壞影響減到最小程度，你的飛行就不會那么緊張了。

　　快速旅行對身體的影響實際上比我們所意識到的更加令人不安。調整的習行因時差而引起的生理節奏的破壞不是必須重新調整去適合不同時區的心理影響。它是由人體內的生理調節結構，特別是荷爾蒙系統在不同環境的變化引起的。感到困惑了嗎?美國國務卿約翰·福斯·特杜勒斯飛往埃及進行關于阿斯旺大壩的談判時也是這樣。后來，他把他的不理想的判斷歸咎于時差反應的不良影響。

　　時差的影響也可以加以利用。約翰遜總統曾經在關島召開重要會議，其所有活動都按華盛頓時間進行。白宮工作人員個個精神煥發，而在這種情況下，當地人卻受時差反應之苦。實際上，好像他們剛剛被飛機送到美國一樣。

　　既然我們懂得了什么是高速飛行時差綜合癥。很自然，這些活動不得不加以調節，人體現人有兩套相互影響的調節系統。

　　一個定時系統表現在我們的感覺和胃以及居住在一個特定時區時，我們所經歷的周期。另一個定時系統在我們的人體時鐘內，這些人體時鐘在不受干擾時，會使人體有一個25小時，是的25小時的生理節奏。一般情況下，這兩種定時器是步調一致的。外部信號常常調節人體時鐘命使之達到更為便利的24小時周期。

　　然而，如果你將整個身體轉移到相差四個小時的時區，這兩個小時鐘就不協調了。就像兩個鬧鐘通常一起設置，但被重新設置時相差了好幾個小時。雖然這兩個時鐘通常會一起鬧時，但現在它們在不同時刻響起。類似的，當太陽升起時身體可能被設定為晚上。

　　經過一段時間以后，生理系統將會重新調整過來。但這的確需要時間。一個容易監測的節律是手掌出汗的節律。血壓也是有節律的，需要四天時間才能得到重新調整。

　　形成這種差異的百不同的身體活動由不同因素的支配。不管身在何處，控制鹽和水分排泄的皮質醇激素是早上產生的。但不論何時睡眠，生長激素是在睡眠中釋放的。通常這兩種激素相隔七、八個小時釋放，但如果人體在一大早到達目的地，并且盡快入睡，這兩種激素將同時釋放。

　　關于這點我們能做些什么呢?等待幾天直到身體適應新的時區是不可取的。幸好，有一條捷徑。它依靠兩點――胃調節其他活動定時的能力和咖啡的藥物作用。

　　基本的道理是：

　　咖啡在早上可以延遲人體時鐘，在晚間可以提早人體時鐘。咖啡在下午三點左右是中性的。食物中的蛋白質使人不眠，而碳水化合物卻使人易于入睡。空腹吃食物幫助人體時鐘準時。