The reason is: 1. Steamed bread and rice contain carbohydrates such as starch. Starch metabolism can produce sugar and energy, but vitamins and minerals are needed in the metabolic process. If the staple food lacks nutrition, it can't be absorbed well.
2. In addition, the first nutrient element that people need for survival is not found in staple food, nor in vegetables and fruits. It is protein (found in meat, eggs and milk).
3. Some people want to live a healthy life and need balanced nutrition. They need to eat high-quality fat, which only exists in nuts.
I study nutrition, so I won't tell the truth. I hope you have a balanced diet and don't have a partial eclipse.