Do a render foreach loop on a regular field?
$field_values = element_children($fields['field1']);
foreach($field_values as $field_value) { ... }


I was looking for the answer to this too, and ended up hunting through the render() function. It wasn't too far down the chain: drupal_render() calls element_children().


  element_children
  
  Identifies the children of an element array, optionally sorted by weight.
  
  The children of a element array are those key/value pairs whose key does not start with a '#'. See drupal_render() for details.