It is a classic playground scare story — if you swallow chewing gum it will stay in your digestive system for seven years.

But according to scientists at the American Chemical Society, the tale is myth as chewing gum is no more harmful than the rest of the food that passes through our digestive system.

When we eat something — whether it be normal foods or chewing gum — it goes through three main phases in our bodies.

The first of these phases is chewing.

With normal foods your teeth and tongue work together to crush the food you eat into tiny bits. Munching your food then triggers muscle movements which move the food through your digestive tract down to your stomach, where muscles churn your chewed up food with digestive juices.

The second phase involves enzymes — biological catalysts that speed up chemical reactions. They are found in your saliva, stomach juices and intestines.

Enzymes kick-start the reactions to break down the food into its constituent parts, whether they are fats from foods such as cheese, carbohydrates from food such as pasta, or proteins from meat or nuts.

Stomach acid, which is made up of hydrochloric acid and salts, leads the third phase of digestion. This harsh brew dissolves chewed food into a slurry so your intestines can handle it. After this point, whatever remains goes straight down the toilet.

The main difference when processing chewing gum is that you don’t crush the chewing gum down into tiny bits — that would somewhat defeat the purpose of chewing gum. Instead, if you swallow the gum, it will go down in one big wad before it enters the enzyme phase.

Most of the molecules in gum are carbohydrates, oils and alcohols. As with any other food, on their own these molecules are easily broken down. However, we don’t have an enzyme for the rubber polymers so the gum passes through to phase three. While stomach acid is strong, it still can’t dissolve the rubber polymers in the chewing gum. Yet the human body has no problem moving that lump of gum through the digestive system and out the other end within a day or two.

有个经典的大人拿来吓唬小孩的谎言— 如果你吞了口香糖，它将在你的消化系统里住七年。但是据美国化学学会的科学家

称，这并非事实，嚼过的口香糖和其他经过我们肠胃的其它食物一样没什么危害。

我们进食时 — 不管是正常的食物还是口香糖 — 都会在消化道内经历三个主要阶段：

第一阶段是咀嚼。进食普通食物时，你的牙齿和舌头协同工作，将你吃进去的食物嚼成小小的碎末。

用力咀嚼食物带动肌肉运动，这会把食物通过食道运送到胃里，胃部肌肉用胃酸搅拌你咀嚼过的食物。第二阶段涉及到酶，这是一种可以加速化学反应的生物催化剂。消化酶主要存在于唾液、胃液和小肠液中。

酶能启动化学反应，将食物分解为一些基本成分，比如从奶酪里分解出脂肪，从意大利面里分解出碳水化合物，或者从肉类、坚果类分解出蛋白质。

第三个消化阶段由胃酸引导。胃酸由盐酸和盐组成。这种非常厉害的消化液可以把咀嚼过的食物分解为泥浆状，这样你的肠道就可以处理它们了。

经过此步之后，剩下的东西就以粪便形式排出体外。处理口香糖，和其他食物最大的不同在于口香糖不能被分解成小块——如果真嚼碎了，一定程度上就没有达到嚼口香糖的目的。因此，如果你将它吞下去了，它是整个一团进入酶消化阶段。

口香糖里的主要成分是碳水化合物、油类和醇类。与其他食物一样，这些分子很容易分解。然而，我们没有能分解橡胶聚合物的酶类，所以口香糖来到了第三个阶段。尽管胃酸很强大，它也不能分解口香糖中的橡胶聚合物。但人体完全可以把这一团口香糖清除出消化系统，这头进那头出只要一两天时间。(Chinadaily.com.cn)

    Words to Learn 相关词汇

   【虚构】xūgòu myth any invented story, idea, or concept

    【咀嚼】jǔjué munch chew or eat (something) especially in a noisy way