Is it possible to overwrite _source field mapping to add/remove fields?

Elastic Stack Elasticsearch
1

Is it possible to overwrite an existing _source field mapping to add/remove
fields?

This is an existing mapping.

{
"article": {

"_source": {
  "includes": ["item.@*", "item.displayData", "item.itemType.*"]
}

}
}

I tried to remove "item.itemType.*" so that it's not included in "_source".
But mapping GET doesn't show any change. Same thing happens if I try to add
any new field to be included. Not sure if ES supports this.

Thanks,
Yadu