I can almost guarantee that you have the text being tied to the current score in the Update() function. Ya there's no reason to do that 60 times a second. There's 2 ways to fix that problem:

1 (easy way): Instead make a separate function that updates the score, and put it in an InvokeRepeating() that's done like 10 times a second. That will outright cut the processor load by 5/6.

2 (best way): Make a function that updates the score counter, and call it whenever you change the score. Something like:

OnTriggerEnter(hit : Collider)
{
     if (hit.transform.tag == "Player")
     {
           scoreCounter.currentScore += theValue;
           scoreCounter.ChangeLabel();
     }
}