I have a hypothesis as to why this might be. I think that many cases of tinnitus derive from misfiring neurons, possibly due to neuro-chemical imbalances. To the extent that serotonin is involved, eating may play a role in altering these neuro-chemical levels because much of the body's serotonin is generated in the gut.
I too find that my tinnitus is affected by food, but in a somewhat different way. If my stomach is riled, due to spicy food for example, I will often notice that my tinnitus is louder upon waking. Once my stomach calms down, the tinnitus subsides, and sometimes vanishes altogether.
-Golly