Difference between Nutrition and Digestion

Key Difference: Nutrition is the process of obtaining and utilizing food by organisms. It can be also described as the body's ability to use and metabolize food. On the other hand, Digestion refers to the process of breakdown of food for the utilization of nutrients. It can be achieved chemically or mechanically. Nutrition involves the process of digestion.

Nutrition is the process of obtaining and utilizing food by organisms. It includes all the processes by which a body takes, digests, absorbs and then later uses food. It is not only the consumption of food, but it also includes the use of nourishing material present on the food. Thus, it can be called as the sum of all these processes (ingestion, digestion, absorption, assimilation and egestion).

Humans make use of carbohydrates, proteins and fats for obtaining some key products. Carbohydrates, proteins, and lipids (fats), as well as fiber, vitamins, minerals, and water are known as the essential nutrients for life. Good nutrition depicts the existence of a well-balanced diet and a regular physical activity. The utilization of food substances is done for various purposes like growth, repair and maintenance of the body. Nutrition is also a branch of science which deals with nutrients and nutrition, particularly in humans.

Digestion refers to the process of breaking down of food into molecules that can be utilized by body cells. It occurs at levels like multicellular, cellular and sub-cellular levels. In most vertebrates, this process includes various stages. Typically, it includes mechanical manipulation and some chemical actions. It is basically a form of catabolism and can be simply stated as a breakdown of macro food molecules into the smaller ones.

In mammals like human, food is taken in through mouth, where it is chewed by teeth. Salivary Amylase breaks starch and glycogen onto smaller carbohydrates. Through Esophagus, it enters the stomach. Acid in the stomach assists in killing the contaminating microorganisms. The mechanical breakdown and chemical alteration of some food further takes place. Then the obtained product goes to the small intestine via large intestine. The products of digestion are used for either cellular respiration or biosynthesis. The undigested product is excreted during defecation. It is important to mention that other organisms use some other mechanisms to digest food.

Comparison between Nutrition and Digestion:

	Nutrition	Digestion
Definition	Nutrition is the process of obtaining and utilizing food by organisms	Digestion refers to the process of breakdown of food for the utilization of nutrients.
Process	Sum of all these processes (ingestion, digestion, absorption, assimilation and egestion)	It involves mechanical digestion - mixing and churning - and chemical digestion - using enzymes.
Types	Autotrophic – organisms produce their own food by using raw materials Heterotrophic – organisms feed on Autotrophics	Mechanical – food is crushed into smaller pieces in order to increase its surface area. Chemical – carried out by the digestive enzymes (example – Bile produced by liver helps in breaking down of fats)