What Are Carbohydrates?
Carbohydrates are one of the three main macronutrients found in food, alongside protein and fat.
They are found naturally in many foods, including fruits, vegetables, grains, beans, lentils, milk, and some dairy products.
Carbohydrates are often discussed as if they were one type of food.
But carbohydrates are actually a broad group of nutrients with very different characteristics.
Sugar, starch, and fiber are all carbohydrates, yet the body handles them differently.
This is why simply asking whether a food is “high in carbohydrates” doesn’t tell you whether it is a good or poor choice.
To understand carbohydrates, it helps to look at what type of carbohydrate a food contains, where it comes from, and what else comes with it.
What Are Carbohydrates Made Of?
Carbohydrates are molecules made primarily from carbon, hydrogen, and oxygen.
From a nutrition perspective, carbohydrates are commonly divided into three broad groups:
- Sugars
- Starches
- Fiber
Sugars and starches can be digested and used as sources of energy.
Fiber behaves differently because it is not fully digested by the human digestive system.
This distinction is important because two foods can both contain carbohydrates while having very different effects and nutritional profiles.
What Do Carbohydrates Do?
One of the main roles of digestible carbohydrates is to provide energy.
During digestion, many carbohydrates are broken down into glucose and other simple sugars that the body can use.
Glucose can be used by cells as an energy source.
Carbohydrates can therefore be an important part of a varied diet.
But carbohydrates are not only about energy.
Foods containing carbohydrates can also provide:
- Fiber
- Vitamins
- Minerals
- Water
- Plant compounds
- Protein
- Other nutrients
That is why it is useful to consider the whole food, rather than looking at carbohydrate grams alone.
The Three Main Types of Carbohydrates
Sugars
Sugars are relatively simple carbohydrates.
They can occur naturally in foods or be added during food production.
Naturally occurring sugars are found in foods such as:
- Fruit
- Milk
- Some vegetables
Added sugars can be found in products such as:
- Soft drinks
- Desserts
- Sweetened cereals
- Cakes
- Biscuits
- Sweetened beverages
The presence of sugar alone doesn’t describe the complete nutritional value of a food.
For example, whole fruit contains naturally occurring sugars along with fiber, water, vitamins, minerals, and other plant compounds.
Starches
Starches are complex carbohydrates made up of many linked glucose units.
They are found in foods such as:
- Potatoes
- Corn
- Rice
- Oats
- Wheat
- Bread
- Pasta
- Beans
- Legumes
Starchy foods can provide energy as well as other nutrients.
The nutritional profile depends greatly on the food itself and how it is prepared.
For example, a bowl of oats and a highly processed sweetened cereal may both contain carbohydrates, but they are not nutritionally identical.
Fiber
Fiber is also a type of carbohydrate, but the body does not fully digest it.
It is found naturally in plant foods such as:
- Fruits
- Vegetables
- Whole grains
- Beans
- Lentils
- Nuts
- Seeds
Different types of fiber behave differently in the digestive system.
Some can hold water, some can add bulk, and some can be fermented by gut microorganisms.
If you want to understand fiber in more detail, see our guide:
What Is Fiber? A Simple Guide to Fiber in Food
Are All Carbohydrates the Same?
No.
This is one of the most important ideas to understand about carbohydrates.
Consider these foods:
- An apple
- Oatmeal
- Lentils
- A soft drink
- A slice of whole-grain bread
- A sweetened pastry
All can contain carbohydrates.
But they don’t provide the same nutritional package.
An apple also provides water, fiber, vitamins, minerals, and plant compounds.
Lentils provide carbohydrates together with protein and fiber.
A soft drink can provide a substantial amount of sugar with little fiber or protein.
A pastry may contain carbohydrates together with fats, sugars, and other ingredients.
So the word “carbohydrate” doesn’t tell you enough about a food by itself.
Simple Carbohydrates vs. Complex Carbohydrates
You may have heard carbohydrates described as “simple” or “complex.”
Simple carbohydrates generally include sugars, while complex carbohydrates include starches and fiber.
This classification can be useful as a basic introduction, but it doesn’t completely describe the nutritional quality of a food.
For example, fruit contains simple sugars but also provides fiber and other nutrients.
Likewise, not every food containing complex carbohydrates has the same nutritional profile.
A more useful approach is to look at:
- The type of carbohydrate
- The amount of fiber
- The degree of processing
- Added sugars
- The other nutrients in the food
- The portion and overall eating pattern
What Is the Difference Between Naturally Occurring and Added Sugars?
This distinction is useful when reading nutrition information.
Naturally occurring sugars are found naturally in foods.
Examples include:
- Fruit
- Milk
- Some vegetables
Added sugars are added to foods or beverages during preparation or manufacturing.
Examples include sugars added to:
- Soft drinks
- Sweetened coffee drinks
- Desserts
- Sauces
- Cereals
- Packaged snacks
The presence of naturally occurring sugar in a whole food does not make that food nutritionally equivalent to a food or drink containing added sugar.
Looking at the entire food is important.
Carbohydrates and Blood Glucose
When digestible carbohydrates are broken down during digestion, glucose can enter the bloodstream.
The body regulates blood glucose using several mechanisms, including the hormone insulin.
However, different carbohydrate-containing foods can affect blood glucose differently.
Factors can include:
- The type of carbohydrate
- The amount of fiber
- The physical structure of the food
- How processed the food is
- What other foods are eaten with it
- The amount consumed
This is one reason it is too simplistic to classify all carbohydrates as either “good” or “bad.”
Why Fiber Changes the Conversation
Fiber is particularly important when thinking about carbohydrates.
Because fiber is not fully digested, it behaves differently from digestible sugars and starches.
Foods that naturally contain both carbohydrates and fiber can therefore have a different nutritional profile from foods that provide mostly rapidly digestible carbohydrates.
For example:
Whole fruit
Carbohydrates + fiber + water + micronutrients.
Beans
Carbohydrates + protein + fiber + micronutrients.
Sugary drink
Mostly carbohydrates from sugars, with little or no fiber.
The carbohydrate number alone doesn’t capture these differences.
Whole Grains vs. Refined Grains
Grains can be processed in different ways.
Whole grains generally retain the bran, germ, and endosperm of the grain.
Examples include:
- Oats
- Brown rice
- Whole-wheat bread
- Whole-grain pasta
- Barley
Refined grains have had parts of the grain removed during processing.
Examples include many products made with refined wheat flour and white rice.
Refining can change the fiber and nutrient content of a grain.
Some refined grain products are also fortified with selected nutrients, so the nutritional profile depends on the specific food.
This is why looking at the nutrition label and ingredient list can be more informative than judging a food simply by its color or name.
Are Carbohydrates Necessary?
Carbohydrates can be an important source of energy in the diet.
The body can also obtain energy from other macronutrients, so the question is not simply whether carbohydrates are “good” or “bad.”
What matters is the overall dietary pattern and the types of carbohydrate-containing foods being eaten.
Carbohydrate-rich foods can provide valuable nutrients, particularly when they come from foods such as:
- Fruits
- Vegetables
- Whole grains
- Beans
- Lentils
At the same time, foods high in added sugars can contribute substantial amounts of energy without providing the same range of nutrients.
The source matters.
How to Choose Carbohydrate Foods
Instead of trying to avoid carbohydrates altogether, it can be more useful to ask a few simple questions.
Does the Food Provide Fiber?
Foods containing naturally occurring fiber can contribute to overall fiber intake.
What Else Comes With the Carbohydrate?
Look at protein, fats, vitamins, minerals, and other nutrients.
Is Sugar Naturally Occurring or Added?
This can help you understand the nutritional context.
How Processed Is the Food?
Processing isn’t automatically bad, but different forms of processing can change a food’s nutritional characteristics.
How Does It Fit Into the Meal?
The rest of the meal matters too.
A carbohydrate-containing food eaten alongside vegetables, protein, or healthy fats creates a different meal than the same carbohydrate eaten in isolation.
Carbohydrates in Everyday Meals
Carbohydrates can appear in almost every type of meal.
Breakfast
Examples include:
- Oats
- Whole-grain toast
- Fruit
- Plain yogurt with fruit
Lunch
Examples include:
- Rice
- Whole-grain bread
- Beans
- Vegetables
- Fruit
Snacks
Examples include:
- Fruit
- Oat-based foods
- Nuts with fruit
- Whole-grain snacks
Dinner
Examples include:
- Rice
- Potatoes
- Whole grains
- Beans
- Vegetables
The goal isn’t to eliminate carbohydrates.
It is to understand the different foods that provide them.
A Better Way to Think About Carbohydrates
Instead of asking:
“Are carbohydrates bad?”
try asking:
What Type of Carbohydrate Is It?
Sugar, starch, and fiber behave differently.
Where Does It Come From?
A whole fruit is different from a sugary drink even though both contain carbohydrates.
What Else Does the Food Provide?
Look beyond carbohydrate grams.
How Much Processing Has It Undergone?
Processing can change the physical and nutritional characteristics of foods.
How Does It Fit Into the Overall Diet?
One food rarely tells the whole story.
This approach gives you a much more useful understanding of carbohydrates.
The Simple Takeaway
Carbohydrates are one of the three major macronutrients.
They include sugars, starches, and fiber, which behave differently in the body.
Carbohydrates can come from nutritious foods such as fruits, vegetables, whole grains, beans, and lentils, as well as foods and drinks that contain large amounts of added sugars.
So carbohydrates should not be judged simply as “good” or “bad.”
A better approach is to look at:
The type of carbohydrate, the food it comes from, what else the food provides, and how it fits into the overall diet.
Once you start looking beyond the carbohydrate number on a nutrition label, it becomes much easier to understand the difference between different carbohydrate-containing foods.
Sources & Further Reading
Harvard T.H. Chan School of Public Health — The Nutrition Source: Carbohydrates
Background information on carbohydrates, sugars, starches, fiber, whole grains, and carbohydrate-containing foods.
Harvard T.H. Chan School of Public Health — The Nutrition Source: Fiber
Additional information about dietary fiber and how different types of fiber behave in the digestive system.
U.S. Food and Drug Administration — Added Sugars
Information about added sugars and how they are presented on Nutrition Facts labels.