Carbohydrates, or “carbs”, have a bad rap. They have been demonized for years, we’ve been told to limit them in our diets, and they’ve been labeled as the enemy. As it turns out, they are not the demons they have been made out to be, and learning how to incorporate the various types of carbohydrates into a healthy diet is beneficial for our overall health.
What are Carbohydrates?
Carbohydrates are one of the 3 macronutrients, along with protein and fat, found in food and drinks. Carbohydrates function as a source of energy and play key roles in glucose and insulin action, as well as cholesterol and triglyceride metabolism and fermentation (1).
From a structural perspective, carbohydrates are classified into simple and complex carbohydrates. Simple carbohydrates consist of single and double monosaccharide (sugar molecules) units, while complex carbohydrates consist of short and long chains of monosaccharide units. The exact structure of carbohydrates found in food and drinks determines what types of carbohydrates it contains.
What are the 3 types of carbohydrates?
There are 3 main types of carbohydrates:
- Sugars
- Starches
- Fibers
Sugars are classified as simple carbohydrates, given they are single or double units of sugar molecules, while starches and fibers are classified as complex carbohydrates, as they are made up of long chains of sugar molecules. Most foods contain multiple types of carbohydrates.
Sugars
Sugars are the most basic forms of carbohydrates. Sugars are made up of monosaccharides (glucose, fructose, and galactose) and disaccharides (sucrose, maltose, and lactose). The simplest form of sugar is glucose, which is the body’s primary source of energy. Due to their simple structure, sugars are easily and quickly digested by the body. Sugars are naturally present in many whole foods, including fruits, vegetables, and dairy, and can also be found in refined formats in processed foods. Sources of sugars include:
- Fruits
- Fruit juice
- Vegetables
- Honey
- Maple syrup
- Dairy products
- Sugar (white sugar, brown sugar, cane sugar, coconut sugar, etc.)
- Candy
- Soda
While both whole foods and processed foods contain sugar, the natural sugars found in whole foods, such as fruits, vegetables, and dairy, are found in the presence of fiber, protein, and/or micronutrients, while the sugars found in ultra-processed foods are added sugars, which contain little to no nutritional value. Therefore, the sugars found in whole foods have a much greater nutrient density than those found in refined carbohydrates.
Starches
Starches are complex carbohydrates, which are made up of long chains of sugar known as polysaccharides, which are the most abundant and relevant to the human diet. Starch is the storage form of carbohydrate in plants and the body breaks down starches into glucose, which is used for energy. A special form of starch, known as resistant starch, has been shown to be particularly valuable for digestion and gut health (2). Starches are primarily found in whole grains, grain products, legumes, and root vegetables. Sources of starches include:
- Oats
- Rice
- Brown Rice
- Corn
- Peas
- Beans
- Lentils
- Potatoes
- Sweet potatoes
- Squash
- Grain products (cereal, pasta, etc.)
Compared to sugars, starches take longer to digest and, therefore, their energy release is slower, however, the more refined a starch is, the more quickly it is digested and the more potential to spike blood sugar. For instance, while wheat berries and wheat flour are both sources of starch, refined wheat flour contains far less fiber than wheat berries, the whole grain form of wheat.
Fibers
Fibers are also a form of complex carbohydrates and are plant-based compounds that include a wide range of non-starchy polysaccharides that are not fully digested by the human gut. Types of dietary fiber include beta-glucan, cellulose, hemicellulose, gums, pectin, and mucilage. Sources of fibers include:
- Fruits
- Vegetables
- Whole grains
- Beans
- Lentils
- Nuts
- Seeds
Fiber has been shown to lower all-cause and cardiovascular-related mortality and reduce the incidence of coronary heart disease, type 2 diabetes, and colorectal cancer (3). Moreover, high-fiber diets have been shown to promote greater weight loss and dietary adherence independently of macronutrient and calorie intake (4). Learning how to eat more fiber is highly beneficial for overall health.
Sugar vs. Starch vs. Fiber
While there are 3 primary types of carbohydrates, it is important to understand that almost all carbohydrate-containing foods, especially whole foods, contain multiple types. Carbohydrate-containing foods are simply classified by the type of carbohydrate they contain most. Here is a comparison of the sugar, starch, and fiber content in an apple, oats, and kale (5, 6, 7).
| Type of Carbohydrate (per 100 grams) | Apple | Oats | Kale |
| Sugars | 11.8 grams | 0.9 grams | 0.5 grams |
| Starch | 0.9 grams | 46.6 grams | 0.1 grams |
| Fiber | 2.1 grams | 10.1 grams | 3.8 grams |
| Total Carbohydrates | 14.8 grams | 67.7 grams | 4.4 grams |
How many calories are in carbohydrates?
Carbohydrates in the form of sugar and starch provide 4 calories per gram, while fibers contain an average of 2 calories per gram (8).
What are total carbohydrates?
Total carbohydrates include all three types of carbohydrates: sugar, starch, and fiber. On a nutrition facts label, total carbohydrates are listed with a breakdown of sugar and fiber. Although starch is not listed, it can be calculated by subtracting the number of grams of sugar and fiber from the total grams of carbohydrates.
What are net carbs?
Net carbohydrates, or “net carbs”, is the total amount of carbohydrates minus the amount of dietary fiber and or sugar alcohols found in food. While the term does not have an official scientific definition, net carbs are calculated based on the assumption that are not absorbed or metabolized, however, this is not always true as some forms are still partially digested and provide calories (9).
How many carbohydrates should I eat a day?
There is no one-size-fits-all solution when it comes to carbohydrate intake. The optimal amount of carbohydrates an individual should consume is dependent upon their age, sex, activity level, and goals. While dietary guidelines recommended a dietary fiber intake of 14 grams for every 1,000 calories per day, or, about 25 grams for women and 38 grams for men each day, there is no specific recommendation for total carbohydrate intake (10). On average, individuals should aim to consume 45 – 65% of total calories from carbohydrates.
Is a low-carb diet safe and healthy?
Low-carb diets are considered safe and healthy as long as they contain a wide variety of nutrient-dense, unprocessed, whole foods. Due to a process called gluconeogenesis, where the liver can convert non-carbohydrate substrates to glucose, the body can produce enough glucose to support essential body functions. Generally speaking, if an individual is consuming adequate calories, protein, fiber, vitamins, and minerals, low-carb diets are generally safe to consume. Although, individuals with specific health and performance goals, such as athletes and individuals looking to build muscle, can benefit from a higher carbohydrate intake (11, 12, 13). It is best to work with a registered dietician or certified nutrition coach if you are unsure.
What types of carbohydrates are healthiest?
The healthiest sources of carbohydrates are unprocessed, whole foods carbohydrates – fruits, vegetables, root vegetables, whole grains, beans, and lentils. By consuming most of your carbohydrates from whole foods, you can ensure that you are consuming nutrient-dense foods rich in vitamins and minerals, as well as supporting adequate fiber intake.
Which types of carbohydrates should I eat?
Here are some simple tips to keep in mind when it comes to what types of carbohydrates to consume:
- Aim to consume more natural sugars (e.g. fruit) than refined sugars (e.g. white sugar).
- Aim to consume more whole grains (e.g. oats) than grain products (e.g. pastries).
- Aim to consume a source of starch (e.g. rice, potato, sweet potato, beans, lentils, etc.) and fiber (e.g. fruit or vegetable) at every meal.
The Bottom Line
Carbohydrates are classified by their structure and the 3 primary types of carbohydrates are sugars, starches, and fibers. Sugars are found in fruits, vegetables, and dairy products, starches are found in whole grains, legumes, and root vegetables, and fibers are found in fruits, vegetables, grains, beans, and lentils. Carbohydrates are also found in processed foods, such as baked goods, candy, and soda, however, it is best to consume whole-food carbohydrate sources as they are more nutrient dense and can better support overall health.
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