"According to the Bulletproof website, Upgraded Coffee is essential to the Bulletproof mix: regular coffee contains toxins that make you all jittery, but Upgraded Coffee, the result of a decade-long search, does not. (A canny businessman, Asprey does not divulge the origin of the beans that make up Upgraded Coffee. The website, however, describes it as well-balanced, with a full body and creamy finish, with hints of apple, cherry, and vanilla.) So maybe if I’d had my butter coffee with Upgraded Coffee beans, my leg would not be jiggling right now as I type this. (Or maybe he’s full of shit, since regular coffee doesn’t contain threatening levels of toxins either.)
Anyway, Asprey writes that he was inspired to put butter in his coffee during a freezing trek through Tibet, when, cold and weary, he stopped at a guesthouse to drink tea flavored with yak butter and was "literally rejuvenated." (The snotty former English major in me wants to say, "So he actually died and came back to life, like a vampire?" But who am I to question a revolution in warm beverage technology?) Butter, he writes, contains "all the benefits of healthy milk fat with none of the damaging denatured casein proteins found in cream.""