I've been reading this from a lay-persons semi pragmatic viewpoint. From what I understand about Sinemet, the L-Dopa is used by the body to produce dopamine. Unlike the body's natural demand and supply process of dopamine production, L-Dopa get's converted even if it isn't required, leading to excess levels and shake side effects since it isn't stored effectively. A bit like drinking from a cup at a variable rate, the trick is to keep it topped up not overflowing or empty, both of which have consequences.
What the eck has this to do with Bananas then? Along with many of our meds, there is often a natural food source that provides the chemicals required. The trick is finding out how quickly and effectively that food converts into the chemical required. Then balancing what you get from food and what from meds is down to your experience.
Provided you can balance the timing, it seems Bananas could help you cope on less meds. You'll need to know what size of Banana and what affects its absorption rate so it's another complication, albeit 'natural'. And then there's all the other foods to try. Sometimes the meds seem the simplest option.