In the big picture, there is no difference between the two. You
can look at anything that provides nutrients to the body like
carbohydrates, protein, and fats. Food in general is just a carrier
for nutrients. For example, take a loaf of bread – it has starch in
it and protein and non-fat dry milk, the non-fat dry milk also
contains lactose. It will also contain a high amount of minerals.
The non-fat dry milk will contain casein, which is a non-fat milk
protein. When you eat food, you break down the food to get
nutrients for the body.
