What is the primary function of carbohydrates in the human body?

The primary function of carbohydrates in the human body is providing energy. Carbohydrates are the body's preferred and most readily available source of fuel.

When carbohydrates are consumed, they are broken down during digestion into simple sugars, primarily glucose. Glucose enters the bloodstream and is transported to cells throughout the body, where it undergoes cellular respiration to produce adenosine triphosphate (ATP), the molecule cells use for energy. The brain alone relies almost exclusively on glucose as its energy source.

Carbohydrates provide approximately 4 kilocalories (17 kilojoules) of energy per gram. They are classified into:

• Simple carbohydrates (sugars): found in fruits, milk, and table sugar. They provide quick energy.
• Complex carbohydrates (starches and fibre): found in grains, legumes, and vegetables. Starches provide sustained energy, while fibre aids digestion.

The other options describe functions of different nutrients:

• Aiding in the digestion of proteins is not a primary carbohydrate function.
• Regulating body temperature is primarily managed by water, the circulatory system, and metabolic processes, not by carbohydrates specifically.
• Building and repairing tissues is the primary function of proteins, not carbohydrates.