If we look at "food" more generically, rather than bananas specifically, we are literally in that situation where every person has to have X amount per day or they will die. And competition still works great.

There are two things that set healthcare apart here. One is that sometimes people need unusual treatments to stay alive that are extremely expensive, and our desire not to let people die is at odds with the normal market mechanism where products that cost too much just don't get purchased. The other is that sometimes people have emergencies so urgent they can't really choose their provider.

But the vast majority of healthcare doesn't fall into those categories, and normal market mechanisms work fine for those. Competition would lower prices for most healthcare just like it does for food and everything else.