“At the beginning of yoga practices (especially pranayama) consumption of milk and ghee in the food is recommended. Later, when the practice is firmly established, there is no need to strictly follow these rules." Regarding this 14th sloka in chapter 2, Jyotsna’s commentary of Hathapradipika offers further clarification that the "practice is firmly established when complete success is achieved in the ‘kevala’ kumbhaka.”
Members of TTC 2013 have been happily abiding by this sloka, having each consumed at least one kilo of ghee in less than four weeks (actually, much more than that, in many cases). After adding copious amounts of ghee to our diets, one classmate claimed that her joints popped less in asana class. Another could feel how nourishing ghee was for her nervous system, as “doing a lot of pranayama can really dry you up inside.”
Fat for nerves and for good prana conduction. Makes sense methinks.