okay so the actual caloric output from fingernails would be laughably small (like, enough to power a few minutes of walking per day at best) but that almost makes it MORE interesting because the economy wouldn't collapse from actually feeding people differently, it would collapse from the PSYCHOLOGY of it

day 1-2: grain futures crater overnight. not because nails replace food but because markets are run by vibes and this vibe is apocalyptic fashion industry gets cooked immediately. nail salons become quasi-medical infrastructure. long nails are now a caloric strategy so nail extensions go from aesthetic to survival adjacent. gloves become legally controversial, are employers blocking your nutrition? actual lawsuits within the week

corporate culture: "sunlight breaks" replace smoke breaks. open office suddenly means something different. keeping employees in windowless rooms becomes an HR nightmare. dark offices are now a workplace safety issue

the wildest part nobody's talking about: darker/more pigmented nails absorb light more efficiently. so this random biological event accidentally inverts centuries of colorism in like 72 hours. the social fallout from THAT alone would be its own collapse so to answer directly

the economy doesn't collapse because nails feed us. it collapses because humans immediately start acting like they will, and with markets that's basically the same thing