Assimilation refers to the body’s ability to incorporate vital substances from the environment. Eating, drinking and breathing bring needed materials into the body. Assimilation means that the body can take from these raw materials the specific ingredients needed by the body. Of course digestion is essential for assimilation but is not necessarily synonymous with it. Food can be digested in the stomach but not absorbed properly into the blood and lymph as it makes its way through the intestines.