Carbohydrates provide people with energy and are a vital part of a healthful diet.

However, eating too many carbohydrates or choosing the wrong type can lead to weight gain or other health issues.

In this article, we look at the function of carbohydrates, as well as where they come from, how the body processes them, and which ones to choose.

What is the function of carbohydrates?

Sweet potatoes are a good source of complex carbohydrates.
Carbohydrates provide a person with energy. People can also obtain energy from foods containing protein and fats, but carbohydrates are the body’s preferred source.

If a person does not have a good supply of carbohydrates, their body will use protein and fats as an energy source.

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

Carbohydrates break down into glucose in the body. Glucose moves from the bloodstream into the body’s cells with the help of the hormone insulin. All of the cells in a person’s body use glucose to function.

The brain uses 20–25% of a person’s glucose when they are at rest and is reliant on a constant supply.

Where do carbohydrates come from?
People get their carbohydrates from food. All plants contain carbohydrates, which typically represent a significant portion of people’s dietary intake.

Carbohydrates comprise sugar molecules called saccharides. These molecules contain carbon, hydrogen, and oxygen.

Types
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 longer, more complex chains of sugars. They include oligosaccharides and polysaccharides. Complex carbohydrates also contain fiber and starch.

Examples of complex carbohydrates include:

• whole grains, including some types of bread, cereal, pasta, and rice
• peas and beans
• vegetables and fruits
• Refined carbohydrates
• Refined carbohydrates are foods that have gone through processing that removes some of their ingredients, such as fiber and minerals.

These carbohydrates include sweeteners and high fructose corn syrup, which manufacturers often add to processed foods.

Examples of refined carbohydrates include:

• 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 is already storing enough energy and does not require more, it converts the glucose to fat, which can lead to weight gain.

Glucose cannot stay in the bloodstream, as it can be damaging and toxic. After a person eats, the pancreas releases insulin to help move glucose into the body’s cells, which can use or store it.

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

A diet that contains lots of sugary foods and carbohydrates can cause too much reliance on the insulin response, which may lead to health issues such as diabetes or obesity.

Healthful vs. unhealthful carbohydrates
When a person eats more carbohydrates than they need, they can store the excess glucose as fat. If someone is very active or doing a lot of exercise, they may use up these carbohydrates relatively quickly.

However, people who do not use up these carbohydrates may find that they put on weight.

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

Choosing complex carbohydrates and starchy vegetables can be a more healthful way for a person to include this vital macronutrient in 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 carbohy drates, and they can be a great staple of a nutritious diet.

Grains make up a significant portion of many people’s diets. The Dietary Guidelines for Americans 2015–2020 recommend consuming 6 ounce-equivalents per day of grains on a 2,000 calorie diet.

At least half of this amount should be whole grains, rather than refined or processed grains.

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

Simple and refined carbohydrates, such as sugary snacks and beverages, white bread and pasta, and white potatoes can have negative effects if a person eats too many of them.

The body absorbs the sugars from these foods very quickly, which can give them a quick burst of energy but does not keep them full for long. This effect may lead to 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
Summary
Carbohydrates are essential for providing the body with energy and helping it function optimally. People may have varying requirements for carbohydrates according to their lifestyle, weight, and activity level.

Most people can ensure that they eat a healthful diet by including complex carbohydrates and limiting their intake of refined carbohydrates.

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