The main differences between whole milk and skim milk are as follows:

1. Low cholesterol: As cholesterol is a "fat-soluble substance", it mainly exists in milk fat, while skim milk contains less fat, so the cholesterol content is reduced by more than 70% compared with whole milk, which belongs to "low cholesterol milk".

2. Low content of fat-soluble vitamins: Vitamins A, D, E and carotenoids are "fat-soluble substances". With the removal of milk fat, their content in skim milk will be greatly reduced, or even almost none.

3. Low calorie: Because the fat content in skim milk is very small, the calorie of skim milk is 45% lower than that of whole milk.

4. Low cholesterol: As cholesterol is a kind of "fat-soluble substance", it mainly exists in milk fat, while skim milk has less fat content, so the cholesterol content is reduced by more than 70% compared with whole milk, which belongs to "low cholesterol milk".

5. Skim milk has little difference with whole milk in protein, lactose, potassium, sodium, calcium and B vitamins.