But as diet and health improved, children and adolescents have, on average, increased in height by about an inch and a half every 20 years, a pattern known as the secular trend in height.

　　【长难句分析图解】

　　篇章超精读

　　①Growth, which rarely continues beyond the age of 20, demands calories and nutrients – notably, protein – to feed expanding tissues.

　　②At the start of the 20th century, under-nutrition and childhood infections got in the way.

　　③But as diet and health improved, children and adolescents have, on average, increased in height by about an inch and a half every 20 years, a pattern known as the secular trend in height.

　　④Yet according to the Centers for Disease Control and Prevention, average height – 5′9″ for men, 5′4″ for women – hasn’t really changed since 1960.

　　参考译文

　　①在 20 岁后人很少继续长高，长高需要热量和营养，特别是蛋白质，以满足组织增长的需求。

　　②20 世纪初期，营养不良和儿童传染病盛行。

　　③但随着饮食和健康的改善，儿童和青少年的身高平均每 20 年增加约 1.5 英寸，这就是被称之为身高增长长期趋势的模式。

　　④然而根据疾病控制与预防中心的数据(男性 5.9 英尺，女性 5.4 英尺)，从 1960 年以来并没有改变过。