All of us eat everyday, but most of us don't understand nutrition (营养). We often make mistakes in talking about good diet.
For example, many people think that food, such as rice, bread and potatoes, will make one grow fat. In fact, those food are very good to one's health. They are good sources of many vitamins (维他命). And in comparison with steak and beef, they contain less amount of calories.
Some people don't like canned or frozen vegetables, because they think fresh vegetables cooked at home are always better. This is again wrong. In fact, whether the vegetables are good or not depends more on how they are prepared. Overcooking, for example, destroys many good qualities of vegetables. Vegetables cooked in too much water can lose a large amount of vitamins.
It is widely believed that extra vitamins provide more energy. But taking more than the body needs doesn't make it function better.
It is also wrong to say that vegetables grown in poor, worn-out soil are lower in vitamins than vegetables grown in rich soil. The vitamins in our foods are in the plants themselves. They don't come from the soil. However the minerals in a plant depend on the minerals in the soil.
In short, there are many false ideas about nutrition. We need to correct them.
This passage is mainly about ______.

A. nutrition
B. vitamins
C. vegetables
D. health