Since you've narrowed down the trigger to food I would put my money on the fact that you're Gluten intolerant.
Nobody wants to hear it because everything they like to eat has some grains in it.
I had the same problem you have, lower back pain, joint pain in my right leg, nerve pain down my right leg and it all subsided when I got off grains. I drank a beer one day and I was reminded that beer is made from grains. Same with the Gin in my favorite Martini.