Most vegetables actually have beta carotene instead of actual Vitamin A. It's a safe version that your body only converts to Vitamin A as it needs it. Anything excess is excreted naturally. This is why vegetable sources of Vitamin A are preferred over meat sources like liver since those store the actual Vitamin A form.

Interesting side fact: This is also why polar bear liver is toxic to eat because of it's massive quantities of Vitamin A. A single liver can have as much as 9 million IU of Vitamin A and human toxicity is generally reached at 300,000 IU.