Halakha is very concerned about eating, precisely because it is a natural, basically animal, process. We eat to assuage our hunger. We eat in order to ensure life, not in order to give it content. It is more basic (and hence, less value-oriented) than other human experiences... As usual, halakha attempts to slip in beneath our skin - in this case, literally. We are not worried about man doing something wrong, but about his transforming his life to one of holiness. Even eating - no, precisely eating! - must be the bearer of holiness, so that holiness not be something I engage in, on Shabbat, or in synagogue, but rather something I AM.
(כו) והמדריגה השלישית אחר הגזל והעריות לענין החמדה, הנה הוא איסור המאכלות, בין בענין הטריפות עצמם, בין בענין תערובותיהן, בין בענין בשר בחלב או חלב ודם וענין בישולי גוים, וענין געולי גויים, יין נסכם וסתם יינם. כל אלה הנקיות בהם צריך דקדוק גדול וצריך חיזוק, כי יש תאות הלב המתאוה במאכלים הטובים וחסרון הכיס באיסורי התערובות וכיוצא בזה. ופרטיהם רבים ככל דיניהם הידועים והמבוארים בספרי הפוסקים. והמקיל בהם במקום שאמרו להחמיר, אינו אלא משחית לנפשו.
(26) The sin which comes third after theft and illicit relations in respect to desire is that of forbidden foods - whether those; that are ritually unclean, or an admixture containing them, or a combination of meat and milk, or suet, or blood, or food cooked by gentiles, or the utensils of gentiles, or the wine used in their libations, or their drinking-wine. Purity in relation to all of these requires great scrutiny and self-strengthening because there is a lust in the heart for good foods and because one must sometimes suffer a monetary loss as a result of admixtures and the like. The prohibitions concerning forbidden foods also involve many details, as is reflected in all of the commonly known laws that are treated in the Halachic writings. One who is lenient in relation to these laws when he has been instructed to be stringent is destroying his soul.
For a set of laws that are pretty exacting, most modern Jews treat kashrut with varying degrees of flexibly. That said, keeping kosher, like other Jewish traditions and customs, endures. Many scholars believe that traditions like keeping kosher are important, because they connect Jewish people to their sense of identity, their history, and their culture. Such traditions have kept the spirit of Judaism alive, even in the darkest of times.
אתמר מפני מה אסרו שכר של עובדי כוכבים? רמי בר חמא אמר רבי יצחק משום חתנות...
רב פפא מפיקין ליה לאבבא דחנותא ושתי. רב אחאי מייתו ליה לביתיה ושתי. ותרוייהו משום חתנות.
It was stated: Why did theyprohibit the beer of gentiles? Rami bar Ḥama says that Rabbi Yitzḥak says: due to "marriage"...Rav Pappa had gentiles bring beer outto the entrance of the store, and he drank there. Rav Aḥai had them bring the beer to his house, and hedrank it there. And both [drank in such a manner] due to a concern of "marriage".
ת"ר (דברים יב, כ) כי ירחיב יהוה אלהיך את גבולך למדה תורה דרך ארץ שלא יאכל אדם בשר אלא לתאבון
It was taught: “When the Lord, your God, expands your boundary…according to every craving of your soul you may eat meat” (Deuteronomy 12:20). The Torah taught as a desired mode of behavior that a person should consume meat due only to appetite.
If you have eaten [forbidden foods], not only touched but absorbed them into your system- you may be more nourished and better fed: but the animal instinct will be aroused more strongly within you, and your body becomes more blunted as an instrument of the spirit. Your heart, instead of being holy, instead of only striving for holiness- namely, your sublimity over everything animal-like, is drawn down to the animal- or become the more apathetic and dulled. Your spirit is now faced with a fiercer battle. and is less equipped for the fight.