Well, if it's a complete myth stemming from no where, it's pretty ironic that eating soon after smoking DOES significantly shorten my buzz personally. I've heard this before and only believed it because in my personal experience, eating within 10 mins of smoking kills my high and shortens my buzz. Not that I think it has this effect on everyone... and IME eating after smoking sativa-heavy bud kills the high even quicker. But correlation does not equal causation... maybe I'm just weird.