Originally this unsourced halacha was on this page:
The sin of bitul Torah is committed when a person forgoes his allotted time to learn in order to do a fruitless action. If one became obligated in a mitzvah, or some other necessary action for life (restroom, hygiene, breath of fresh air, etc.) during his time for learning, it is not bitul Torah as long as he is doing those actions to enhance his learning or maintain his spiritual well being.
To some extent, this may be logical, but on the other hand a source is required because this is not so clear cut whether "a breath of fresh air" is considered a spiritual need or not. Please support or disagree with this, using sources. Thanks.