ELI5: Why do we have to have a very varied diet in order to live a healthy lifestyle when all other animals tend to eat the same thing all the time and get all the nutrients they need?

You don’t actually HAVE to eat a varied and healthy diet. As a species, humans will do just fine if we all eat a very unhealthy diet, reproduce six times between 15 and 20, have three babies die, and drop dead ourselves at 27. This is a valid survival strategy for many species.

The problem crops up when you actually want to live till you’re 80. Then you’ll have to take much better care of yourself.

Car analogy: You don’t have to maintain your car, clean it or buy quality oil and gas if you plan on scrapping it when its three years old. But if you still want to drive it in 30 years, you have to take good care of it.

Explain Like I`m Five: good questions, best answers.