Unit 21　Human Biology

　　众所周知，疾病总是困扰我们的健康，有些秘诀可以帮助我们保持健康。

　　Four Secrets To Never Getting Sick

　　Ever wonder why you always seem to come down with a life interrupting virus this time of year，while other women you know sail through the seasons sniffle­free，cough­free，and ache­free?

　　Follow these simple steps to boost your virus protection：

　　Make Friends With Fresh Air

　　Not only does escaping into the fresh air give you a break from all those germs circulating inside，but going for a stroll can actually boost your immunity.

　　Relaxation Fights Off Colds

　　Being stressed will increase your susceptibility to catching a cold.That may be because，over the long term，it leads to the ongoing release of stress hormones (荷尔蒙)，such as glucocorticoids(粮皮质激素)．

　　Clean Hands Are Everything

　　Cold and flu can spread all too easily through touch.Keep your fingers away from your eyes，nose，and mouth as much as possible，and make sure to master the art of handw­ashing.Soap and water remain your most effective tools there.

　　Enough Sleep Is The Magic Bullet

An occasional restless night is nothing to worry about，but a continuous lack of sleep can hamper your immune(免疫)system's ability to function.Anything short of seven hours nearly triples your odds of catching a cold.