wp_nav_menu and wp_count_posts

I’m showing my custom menu with the wp_nav_menu function.

<?php wp_nav_menu( array( 'theme_location' => 'header-menu' ) ); ?>

Now I want to show how many posts are in a category next to the menu item.

Is it possible to combine wp_nav_menu with wp_count_posts?

Or is there another, better solution?