Each week I try to get one "different" item of produce--something we've never eaten before or don't usually eat or cook with. Some of these start getting added to the regular repertoire--like beets, which I now buy a couple of most weeks when Victor isn't traveling, because he likes them so much. Some of them won't ever get added to the regular repertoire--like sweet potatoes, because I just don't like them that much, and jicama, because Victor just doesn't like it that much.
Why not more than one? At least for us, one has experimentally proven to be a manageable number. When I pick one, I can start thinking right away how I might use it--when I pick several, it's just too complicated and food tends to get wasted.
Last week we tried chayote for the first time. It has a very mild taste, sort of like a cross between a pear (texture) and cucumber (flavor). Most sources say it doesn't need to be peeled, and I have no doubt that the peel is edible, but I found the peel unpalatable--it smelled (and therefore tasted) just like grass, which is not something I care to eat.
We cut the (peeled) chayote into pieces and included it in a tomato-beet-cucumber salad, with a basil-herb vinagrette and walnuts. I hardly noticed it was there, but Victor said he particularly liked it.
Like most whole foods, chayote is associated with particular health benefits; some cultures use the fruit medicinally. And this is part of the point of trying to diversify the mix of things we eat: periodically one food or another becomes a kind of fad--oats are good for your heart, or broccoli fights cancer--as if the fact that food is good for you is news. I imagine some people do add huge quantities of broccoli, or oats, or whatever to their diet as a result of such studies, but that seems misguided.
We just figure that if you vary what you eat, you end up getting the benefits of a lot of different foods. It's easy to fall into dietary ruts. Consciously trying to add something new to the mix each week helps make those ruts shallower, and potentially promotes good health by introducing diverse nutrients and other beneficial properties.