Carbohydrates are one of the major chemical components of lipids, amino acids, purines, pyrimidines, porphyrins, steroids, phosphates and many other minor substances.

They do not have a "primary function". Instead, they are part of the structure of almost all living things:

-?Both DNA and RNA contain carbohydrates as part of their primary structure.

-? Many proteins have carbohydrates attached to them, which are necessary for their proper function.

-? The cell walls of plants, bacteria and fungi are made of carbohydrates.

-? All cells attach complex carbohydrates to their outer surfaces in patterns unique to each species. They are used to send and receive signals and also enable different cells of the same organism to recognize each other.

-? The main product of photosynthesis is the carbohydrate glucose, which plants can then use for energy and to build cell walls that give their bodies shape and strength.

-? Most organisms store energy in the form of starch and other carbohydrates that are easy to synthesize and easy to break down when needed.

-? The primary mechanism by which animals release energy from food (the Krebs cycle) is based on carbohydrates. Food is first broken down into its component parts, which are then converted into carbohydrates and fed into the Krebs cycle to produce energy.

Complex carbohydrates are chains of sugars, the molecular makeup of starchy foods such as potatoes, bread, pasta, and rice. Once exposed to stomach acid, they break down into simple glucose, or sugar.

Carbohydrates are therefore essentially sugars, whether simple or complex. Carbohydrates are easily digested for quick energy in the body. Eating too many carbohydrates promotes fat formation. This is why farmers fatten up cattle by turning to corn to bring them to market. This is why bears prepare for hibernation by overharvesting berries.

There is no nutritional requirement for carbohydrates. It is a non-essential nutrient. The body can utilize other energy sources very efficiently by burning ketones internally and can internally manufacture any sugar the body needs. Many endurance athletes have switched to LCHF or ketogenic diets to provide a longer lasting source of energy during marathons, triathlons and hardcore races.