Not sure if anyone has brought this up yet, but I remember reading something that Brandon wrote in someones book. It was something like "Stormlight makes plants grow." There might be something there with the energy cycle passing down stormlight through consumption and Lyft's boon or whatever it was allowed her to tap into the ambient stormlight in food that was originally absorbed by plants. I'll look for the exact quote, but I'm pretty sure this is what is going on.
Q: For Words of Radiance, could you put a comment about something in the upcoming books, nothing specific, just something I can think about? Something like "Renarin has a spren" you wrote for somebody else in The Way of Kings?
A: [brandon wrote]"Stormlight makes plants grow."