I maintain that the food which is forbidden by the Law is unwholesome.
There is nothing among the forbidden kinds of food whose injurious
character is doubted, except pork (Lev. xi. 7), and fat (ibid. vii.
23). But also in these cases the doubt is not justified. For pork
contains more moisture than necessary [for human food], and too much
of superfluous matter. The principal reason why the Law forbids
swine's flesh is to be found in the circumstance that its habits and
its food are very dirty and loathsome. It has already been pointed out
how emphatically the Law enjoins the removal of the sight of loathsome objects, even in the field and in the camp; how
much more objectionable is such a sight in towns. But if it were
allowed to eat swine's flesh, the streets and houses would be more
dirty than any cesspool, as may be seen at present in the country of
the Franks. A saying of our Sages declares: "The mouth of a swine is
as dirty as dung itself" (B. T. Ber. 25a).
The fat of the intestines makes us full, interrupts our digestion, and
produces cold and thick blood; it is more fit for fuel [than for human
Blood (Lev. xvii. 12), and nebelah, i.e., the flesh of an animal that
died of itself (Deut. xiv. 21), are indigestible, and injurious as
food; Trefah, an animal in a diseased state (Exod. xxii. 30), is on
the way of becoming a nebelah.
The characteristics given in the Law (Lev. xi., and Deut. xiv.) of the
permitted animals, viz., chewing the cud and divided hoofs for cattle,
and fins and scales for fish, are in themselves neither the cause of
the permission when they are present, nor of the prohibition when they
are absent; but merely signs by which the recommended species of
animals can be discerned from those that are forbidden.
The reason why the sinew that shrank is prohibited is stated in the
Law (Gen. xxxii. 33).
It is prohibited to cut off a limb of a living animal and eat it,
because such act would produce cruelty, and develop it: besides, the
heathen kings used to do it: it was also a kind of idolatrous worship
to cut off a certain limb of a living animal and to eat it.
Meat boiled in milk is undoubtedly gross food, and makes overfull; but
I think that most probably it is also prohibited because it is somehow
connected with idolatry, forming perhaps part of the service, or being
used on some festival of the heathen. I find a support for this view
in the circumstance that the Law mentions the prohibition twice after
the commandment given concerning the festivals "Three times in the
year all thy males shall appear before the Lord God" (Exod. xxiii. 17,
and xxxiv. 73), as if to say, "When you come before me on your
festivals, do not seethe your food in the manner as the heathen used
to do." This I consider as the best reason for the prohibition: but as
far as I have seen the books on Sabean rites, nothing is mentioned of
The commandment concerning the killing of animals is necessary,
because the natural food of man consists of vegetables and of the
flesh of animals: the best meat is that of animals permitted to be
used as food. No doctor has any doubts about this. Since, therefore,
the desire of procuring good food necessitates the slaying of animals,
the Law enjoins that the death of the animal should be the easiest. It
is not allowed to torment the animal by cutting the throat in a clumsy
manner, by poleaxing, or by cutting off a limb whilst the animal is
alive. (Friedlander translation)
If any of this seems scientifically questionable, keep in mind that he was writing this with the knowledge of 12th Century science.