le 了 at the end of a sentence with a verb predicate.

1. 
   Yīnwèi hē chá duì shēntǐ hěn hǎo, suǒyǐ tā hē chá le.
   因为喝茶对身体很好，所以他喝茶了。
   Because drinking tea is good for one's health, now he drinks tea.


This sentence implies that the person, 'he', did not drink tea before, but now he has changed. Compare it with the following sentence which does not have the change-of-state le 了.


2. 
   Yīnwèi hē chá duì shēntǐ hěn hǎo, suǒyǐ tā hē chá.
   因为喝茶对身体很好，所以他喝茶。
   He drinks tea because it is good for one's health.


This sentence simply reports the fact that 'he' drinks tea as a habitual action because of its benefits.


3. 
   Tā chī sù le, bié zuò ròu cài.
   他吃素了，别做肉菜。
   He has become a vegetarian now. (Lit. He now eats vegetarian food.) Don't make meat dishes.


This sentence implies that 'he ' used to eat meat. Compare it with the following sentence which does not have the change-of-state le 了.


4. 
   Tā chī sù, bié zuò ròu cài.
   他吃素，别做肉菜。
   He's a vegetarian. Don't make meat dishes.


This sentence does not imply any change. It only states a fact that the person, 'he', is a vegetarian.