Ahara Niyamanam - Dos and Donts of Eating Paan - Pasuram 19

Ahara Niyamanam Pasuram 19
--------------------------------------------

வெற்றிலைமுன்  தின்னாதே  தின்னும்  பாக்கும்
வெற்றிலையின்  அடியுமுனியும்  நடுவில் ஈர்க்கும்
வெற்றிலையும்  பாக்குமுடன்  கூட்டித்  தின்னும்
விதவைக்கு  முதன்முடிவாச்  சிரமத்தார்க்கும்
வெற்றிலையும்  சுண்ணாம்பின்  நிலையுமற்றும்
விரதங்கொண்டிடுநாள் வெற்றிலையும்  பாக்கும்
வெற்றிலை திண்ணனாநிற்கப்  பருகு  நீரும்
விதையென வைத்தது தினலும்  விளக்கினாரே

Swamy Desikan explains to us the rules about chewing paan or betel.

Do not chew betel nuts before you start chewing betel leaves. (no tobacco of-course)
Tip, Bottom (kaambu) and the stems/ thick nerves behind the leaves must be removed.
Betel leaves must be chewed first and then the nuts- we cannot chew both of them at the same time.
Widows, Unmarried Brahmacharis and Sanyasis cannot chew Betel leaves.
The betel leaf, in which calcium or sunnaambu is kept cannot be used. (Yes it has more calcium and will burn the mouth).
On days of religious fasting like ekadashi etc.. (utnil that Vrutham is over) one must not chew betelleaves or Paan.
When eating betel leaves due to those betel nuts - it get struck in the throat - we must never drink water during that.
Betel nuts, which are preserved to be seeds (raw betel nuts - for making seeval) - must not be consumed.

It's very important for us to know the dos and donts of our culture. Swamy Desikan out of his immesnse mercy for this mankind ahd documented all this here.
+
There's also pramanam for this in Dharma Sastras:

वेदोऽखिलो धर्ममूलं स्मृतिशीले च तद्विदाम् ।
आचारश्चैव साधूनामात्मनस्तुष्टिरेव च ॥ २.६॥

Vedas are the ultimate source of our sastras + the lifestyle(s) of learned men and then finally - one's own perception when the above two doesnt give us a clear idea. Swamy Desikan has clearly combined the pramanam from vedas and the way of great Asthikas and given it to us as one grantha for our benefit!