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What’s the function of carbohydrates?

Carbohydrates provide energy to humans and are a vital part of a healthy diet.

Eating too many carbohydrates or choosing the wrong type may however lead to weight gain or other health problems.

In this article, we look at the function of carbohydrates as well as where they originate, how they are processed by the body and which ones to choose from.

What is the function of carbohydrates?

What is the function of carbohydrates?

Carbohydrates provide the energy to a person. People can also get energy from foods that contain protein and fats but carbohydrates are the preferred source for the body.

If a person doesn’t have a good carbohydrate supply, their body will be using protein and fats as an energy source.

However, since protein is vital for so many other essential functions, such as the construction and repair of tissues, the body prefers not to use it for energy.

In the body, carbohydrates break down to glucose. With the aid of the hormone insulin, glucose moves from the bloodstream into the body’s cells. To function all cells in a person’s body use glucose.

When they are at rest, the brain uses 20–25 percent of a person’s glucose and relies on a constant supply.

Where do carbohydrates come from?

People get their dietary carbohydrates. All plants contain carbohydrates which typically constitute a significant portion of the dietary intake of humans.

Carbohydrates consist of molecules of sugar, called saccharides. Such molecules are composed of carbon, hydrogen, and oxygen.


Scientists classify carbohydrates as either simple or complex, depending on how many sugar molecules they contain.

Simple carbohydrates

Simple carbohydrates have one or two sugar molecules and include glucose, fructose, sucrose, and lactose.

Simple carbohydrates naturally occur in:

  • fruits
  • fruit juices
  • milk
  • milk products

Complex carbohydrates

Complex carbohydrates contain lengthier, more complex sugar chains. They comprise polysaccharides and oligosaccharides. Complex carbohydrates include fiber and starch, too.

Complex carbohydrates Examples include:

  • whole grains, including some types of bread, cereal, pasta, and rice
  • peas and beans
  • vegetables and fruits

Refined carbohydrates

Refined carbohydrates are products that have been refined to extract some of its components, such as fiber and minerals.

Such carbohydrates include sweeteners and high fructose corn syrup which is often added to processed foods by manufacturers.

Examples include refined carbohydrates:

  • white bread, pasta, and rice
  • processed breakfast cereals
  • cakes, sweets, and baked goods
  • sweeteners and high fructose corn syrup

How does the body process carbohydrates? 

The body breaks down carbohydrates into glucose to use them as:

  • a steady source of energy for bodily functions
  • a quick and instant source of energy when exercising
  • a reserve of energy that the body stores in the muscles or liver and releases when necessary

If the body already retains enough sugar and does not need more, the glucose is converted into fat, which can lead to weight gain.

Glucose can not stay in the bloodstream, since it can be harmful and toxic. The pancreas releases insulin after a person eats, to help move glucose into the cells of the body that can use it or store it.

Insulin is responsible for preventing a person from getting too high blood sugar levels.

A diet that contains lots of sugar products and carbohydrates can cause too much dependence on insulin response, leading to health problems like diabetes or obesity.

Healthful vs. unhealthful carbohydrates

When a person is eating more carbohydrates than they need, the excess glucose can be stored as fat. If someone is very busy or is doing a lot of exercise, these carbohydrates may be used relatively quickly.

People who don’t use these carbohydrates can find they put on weight, though.

Complex carbohydrates, such as brown rice, whole grain bread, and vegetables, slowly release energy and hold a person more full for longer.

Choosing complex carbohydrates and starchy vegetables can be a healthier way for an person to integrate this essential macronutrient into their diet.

More healthful starchy vegetables include:

  • sweet potato
  • parsnip
  • squash and pumpkin
  • turnip and swede
  • beets
  • yams

Legumes, such as beans and peas, also contain complex carbohydrates, and a nutritious diet can be a great staple.

Grains form a substantial portion of the diets of many people. The 2015–2020 Americans Dietary Guidelines recommend consuming 6 ounce-equivalents of grains per day on a 2,000 calorie diet.

Whole grains should be at least half of this amount, rather than refined or processed grains.

A good way for people to do this is to either search for 100% whole grain products or choose foods with at least 50% whole grains.

Plain and refined carbohydrates, such as sugary snacks and drinks, white bread and pasta, and white potatoes, may have negative effects if a person eats too many.

The body very rapidly consumes the sugars from these foods, which can give them a fast burst of energy but will not hold them full for long. This may result in overeating.

Healthful substitutes

A person could try the following substitutes to maintain a healthful diet:

  • replace white pasta or rice with whole grain types
  • substitute a quinoa salad or baked sweet potato for a white bread sandwich and add vegetables to the meal
  • rather than eating processed breakfast cereals, soak whole grain oats in coconut milk and cinnamon overnight and add blueberries
  • swap out a pizza slice for a healthful and filling soup containing vegetables and lentils or beans


Carbohydrates are essential for energy supply to the body and to help it function optimally. People may have different carbohydrate requirements, depending on their lifestyle, weight and level of activity.

Most people can ensure they eat a healthy diet by including complex carbohydrates and limiting refined carbohydrate intake.

Being mindful of carbohydrate choices can help give a person a good balance of blood glucose and reduce the risk of associated health conditions.

Chukwuebuka Martins

Chukwuebuka Martins is a writer, researcher, and health enthusiast who specializes in human physiology. He takes great pleasure in penning informative articles on many aspects of physical wellness, which he then thoroughly enjoys sharing to the general public.

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