Betel nuts are an intoxicant, and therefore the regulative principles prohibit eating them. Sri Caitanya Mahaprabhu's pastime of fainting after eating betel nuts is a solid instruction to all of us that one should not touch betel nuts, even those offered to Visnu, just as one should not touch grains on the Ekadasi day. Of course, Lord Caitanya Mahaprabhu's fainting had a particular purpose. As the Supreme Personality of Godhead, He can do whatever He likes and eat whatever He wants, but we should not imitate His pastimes.