what about vitamins and minerals?
Vitamins and minerals are quite varied in structure and amount in the foods you eat. They can be found in food in a free form, chemically bound to a larger molecule, or tightly encased inside a food aggregate. In most cases, they are liberated during eating by the mechanical process of grinding. They may also be liberated during the breakdown of the large molecules like proteins and starch, in which they may be encased.
Most vitamins and some minerals have active transports in place for absorption and are taken into the body in very specific ways. These active transports act as shuttles, picking up the vitamin or mineral and taking it through the intestinal cell wall into the body, where it may be directly released or transferred to another transport molecule. Since vitamins and minerals are small and are usually found in much lower levels than amino acids, carbohydrate, and fats, these active transports must select and pull these important molecules out of the food and take them into your body. Active transports require energy to function properly.
Calcium and iron are examples of minerals that are taken into the body by active transport. Most of the water-soluble vitamins have an active transport in place as well, and these active transports are primarily found in the middle section of the small intestine, the jejunum. Some minerals, like iron and calcium, are absorbed in the first part of the small intestine as well as the jejunum. The fat-soluble vitamins (vitamins A, D, K, and E) are absorbed with fat miscelles, and therefore require fat to be present for their full absorption.