use like this:
$id = $user->ID;
And if user is new set $id = 9999
function my_show_extra_profile_fields( $user ) {
if(is_string($user) === true){
$user = new stdClass();//create a new
$id = -9999;
}
$newsletter = esc_attr( get_the_author_meta( '_newsletter', $id ) );
unset($user);
}