laravel wherehas is slow for more than 100k records

Hello All, I have a tables like below,

users

id, name, email

courses

id, course_name, description

and user_courses

id, user_id, course_id

now i am trying to fetch user with assigned courses so in user model i have added code like below,

public function assignedcourses()
    {
      return $this->belongsToMany('App\Course','user_courses','user_id','course_id');
    }

now i am trying to fetch data like below,

$coursemanagers = User::whereHas('assignedcourses')->with('assignedcourses')->get();

But above code is taking more time like more than 3 minutes to display the data. how to optimise above query?

Thank you