How should be a healthy diet?

Very good question. 1)eat what will rot and do it before it does-eat fresh meats fruits veges grains greens and beans. 2)avoid SAD diet= STANDARD AMERICAN diet full of additives preservatives and coloring dyes and preservatives. 3)add essential fatty acids like flax seed or fish oil. If you did this you will be over 90% right.
Colorful. But natural. Focus on a diet that is rich in colorful fruits and vegetables. While grains and lean meats are reasonable to but veggies should serve as the foundation to a healthy diet.