I'm no Turnip, but he's probably still in bed (?) so I thought I'd slip in.
My take is the food as such is far too variable and complex a preparation to be useful. As T says about fava beans - why take ldopa in an unpredictable way when you can have a nice, regulated pill that gets the stuff where it's needed?
So "might" is, er, right. I can't see how anyone will be able to show anything better than a "tendency." i spose vitamins, minerals might be able to be shown to have some causative effect, but there's probably too many variables even here.
I'd stick with the drugs, and eat what's regarded as a good general diet: "Eat food. Not too much. Mainly plants."
But listen to turnip, not me.