At the moment the parameters of food and drinks are limited to "energy" and "water". If you guys would add additional parameters to food and drinks the PVE aspect of the game would increase and certain playstyles would change.
I suggest, you would add two new parameters, namely protein (main sources: meat, fish,insects/worms and some canned food) and vitamine/fibers (vegetables and fruits).
For instance, if a player only eats zucchini from his private garden, he will lack protein and eventually become sick (e.g. Kwashiorkor disease). The same goes with the lack of vitamines/fibers (e.g. more prone to get a cold).
The player is therefore forced to alter his diet.
I suggest, that the players start with 2/3 full of protein and vitamine/fibers reserves. Then both reserves will decrease linear and independend from other activites. The rate of decrease should be slow. If a player has filled up for example his protein reserves and then won't eat anything, that has protein, he should get sick in about 5 to 7 hours gameplay.
Maybe you guys have already planned something similar, in that case: never mind!