I’ve thought of this exact same thing, because of the exact same episode.

I ended up interpreting “cast no shadow” as not being exposed to light under normal circumstances. In other words, a lvl 5 vegan can only eat vegetables that has the edible part under ground. Potatoes, carrots, etc. Fruits and berries are no-go. Maybe even there’s a requirement that said vegetables have to be harveated and eaten at night time to avoid shadows.

Also, I think you intended to put the word “eat” at the end of the title.