Sforno on Leviticus 17:14/ספורנו על ויקרא י״ז:י״ד

1כי נפש כל בשר דמו בנפשו הוא, “for the life-force of all living creatures is its blood” [or contained with its blood. Ed.] (a reference to the way the author described such an almost invisible essence in the blood in his commentary on verse 7).

2בנפשו, including this invisible life-force contained therein. This is because the blood contains something almost intangible. Seeing this ingredient is the closest to anything completely intangible in this terrestrial universe, it is an ideal nutrient for the demons and for those who consort with them. The Torah says:

3ואומר לבני ישראל, although I have permitted the gentiles the consumption of such lifeblood, I have prohibited it to the Children of Israel already in Leviticus 7,26 seeing that the life essence of living creatures is contained in it while the animal was alive and it is liable to transfer some of these animalistic characteristics kind to the persons ingesting it as food. The Torah wants to protect the Jewish people from absorbing more animalistic tendencies than we already possess.