Just kidding! Yes, we do eat most of the food I bring home. In the dark, I grab what looks good, and we sort when I get home.
"But isn't that food diseased?"
No. Places throw stuff out when it hits the sell-by date, gets dirty or crunched, is discontinued, sometimes no discernable reason. I'm reminded of the Seinfeld episode where George ate the donut from the top of the trash. What was wrong with that dounut? Does moving it from the counter or refrigerator to the trash change the chemical composition of the food?
200 years ago, maybe even 100 years ago, we ate fruit that had imperfect spots, drank milk with no sell-by dates (they used a fancy system where they opened the container and smelled the milk), and ate meat that hadn't been in a constant refrigerated state.
So sarcastic rant aside, we test our food using our brains and senses. If it smells bad, away it goes. Many times fruit is past the freshest state, but still perfectly fine and safe to eat. Meat I bring home is still cold from the store, and if still in a sealed package, is cooked thoroughly. For example, I found a 5-pound tube of ground meat. There was a small break in the package, but the meat was still cold, so had just come from the meat case. We saved everything except the portion near the break in the package, and didn't die after eating it.
If there was a ridiculous amount of the same item in the trash that hadn't expired yet, that could be a suspect of tainted food. Often these scares aren't as serious as they're made out to be (bird flu, anyone? Swine flu?). So again, common sense, sound judgment.
I'm not an expert on food science. I just use common sense, and that's gotten us by so far.