system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so hard to figure out the optimal diet for humans?

Seems like with other animals and our pets, we more or less have a good understanding of what they need, and why. And yet when it comes to what WE should eat, it seems like scientists can't agree on anything and there are countless opinions of what we should eat. Why is it so hard to figure out?
gpt
Humans can eat a variety of diets and still be healthy. So long as you get adequate protein, fat, and carbohydrates for your body size, essential vitamins and minerals, some fiber so you can poop, and enough calories, you won't die! At least not right away! It could eventually give you obesity/heart disease/cancer/ diarrhea/bad breath what have you. But that usually takes years and years. People want to live as long as they can without any health problems and that's where you run into trouble because the healthiest diets are pretty plain and don't give you the taste explosion that Doritos and pizza can give you.