Betel is a commonly-consumed (well, chewed) nut in Bhutan, as with a good portion of SE Asia. It is a hard nut containing a mild narcotic that is chewed with a pepper leaf (or other, depending on the region) and some lime (calcium carbonate, not the fruit). to help extract the chemicals from the nut. It gives a mild feeling to the mouth and can cause light-headedness or brief, low-level euphoria. It is a common occurrence in Bhutan (as evidenced by the frequent red stains on sidewalks and streets from people spitting), and you have an option of partaking. Infrequent consumption is not dangerous or toxic, and it is an interesting experience. Be warned: it stains. Your mouth and tongue will turn, briefly, bright orangish-red to red.
Bhutan has a cuisine that is distinct for the country. If you are to enjoy Bhutan, trying the local flavors are, in my opinion, a must. Two things that Bhutanese have with nearly every meal is cheese and chiles. The "national dish" is known as ema datshi, a concoction of a melting cheese and dried chiles, and is found at virtually every meal you'll have in Bhutan, breakfast, lunch, and dinner. That's it. Spoon some over some of the local red rice, and keep a bottle of water handy!! Eventually you'll get used to it, and there are lots of other lovely dishes to try. Among them:
** Yewa datshi - a potato-cheese dish, similar I guess to scalloped potatoes for us Westerners.
** Momo - steamed dumplings filled with either vegetables, chicken, or pork.
** Fried chicken - pan-fried chicken (watch out for bones) with onions and a glaze.
The list goes on, but don't be afraid to venture out of your comfort zone and give them a try. You'll be pleasantly surprised.