Many people swear by vitamin C's ability to ward off colds.是什么意思？

Many people swear by vitamin C's ability to ward off colds.

许多人深信维生素C能预防感冒。

many

adj. 许多，多的；pron. （与复数动词连用）大多数人；

例句
There are many people who still find the act of abortion abhorrent.
仍有很多人对堕胎行为表示厌恶。

people

n. 人，人类，居民，人民，种族；vt. 居住于，布满，使住满人，在…殖民，把动物放养在；

例句
Most people have very little difficulty in seeing why a Van Gogh is a work of genius.
多数人不难理解为什么凡·高的作品是天才之作。

swear

v. 发誓，咒骂；n. 发誓，宣誓，咒骂；

例句
I could kill you! I swear I could!...
我想杀了你！我发誓我真想杀了你！

by

prep. 在…旁边，表示方式，由于，经过；adv. 经过，表示保留或保存时用，短暂拜访；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

vitamin

n. 维生素，维他命；na. “vitamine“的变体；

例句
Since iron destroys vitamin E, these two nutrients should not be taken in conjunction.
铁会破坏维生素E，所以这两种营养物质不应该同时摄取。

ability

n. 能力，资格，能耐，才能；

例句
The public never had faith in his ability to handle the job...
公众从来不相信他有能力胜任这一职位。

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

ward

n. 病房，病室，监视，监督，保卫，[法]受监护人；vt. 监护，守护，挡住，架住，避开，收容；

例句
The ward was busy and Amy hardly had time to talk.
病房里非常忙碌，埃米几乎没有时间说话。

off

prep. 从…落下，离开，从…去掉，下班；adv. 离开，距，离，被取消，下班；adj. 不新鲜的，不能接受，不礼

例句
He eased his foot off the accelerator.
他松开了油门。

colds

n. 冷( cold的名词复数 )，寒冷，伤风，感冒；

例句
Eating oranges keeps colds at bay...
吃橘子可以预防感冒。