Complex carbohydrates take longer to digest and are a more stable source of energy than simple carbohydrates. Complex carbohydrates are present in foods such as bread and pasta. Simple carbohydrates are in foods such as table sugar and syrups.
Complex carbohydrates contain longer chains of sugar molecules than simple carbohydrates. The body converts these sugar molecules into glucose, which it uses for energy. As complex carbohydrates have longer chains, they take longer to break down and provide more lasting energy in the body than simple carbohydrates.
Both types of carbohydrate are often present in many foods. In addition to providing energy via glucose, these foods have many other properties that are important for health.
Which is better?
Carbohydrates provide most of the body’s energy. As a source of energy, complex carbohydrates are the better choice. However, for overall nutrition, it is more difficult to say.
Simple carbohydrates, or sugars, are made up of shorter chains of molecules and are quicker to digest than complex carbohydrates.
This fact means that simple carbohydrates produce a spike in blood glucose, providing the body with a short-lasting source of energy.
The initial spike in energy is responsible for the so-called “sugar rush” that people have long believed follows the consumption of certain simple carbohydrates, such as a chocolate bar or a sugary drink.
However, a 2019 review of studies that included 1,259 participants found no evidence for this, with carbohydrates producing no immediate elevations in mood or activity levels. Instead, the review found a reduction in alertness and increase in fatigue after 30 to 60 minutes.
Complex carbohydrates raise blood glucose levels for longer and produce a more lasting elevation in energy. The primary function of carbohydrates is to provide the body with energy, and complex carbohydrates do this more effectively.
Considering the type of food containing the carbohydrate is important, however.
Some simple carbohydrates are present in healthful foods, such as milk and whole fruits, that contain a variety of necessary vitamins, minerals, and other nutrients.
But some simple carbohydrates are also present in foods with low nutritional value, such as sugary drinks.
Complex carbohydrates are also available in processed foods without much nutrition, such as refined white flour. However, many other complex carbohydrates are in more nutritious foods.
A good example of this is fiber, which is a type of complex carbohydrate and a constituent of plant-based foods. Fiber is necessary for keeping the digestive system healthy.
While complex carbohydrates are a better source of energy than simple ones, they are not necessarily healthier.
Some forms of simple carbohydrates are healthier than some complex carbohydrates. Therefore, it is more useful for people to consider the overall nutritional profile of each food they may want to eat instead of focusing on a single nutrient, such as the type of carbohydrate it contains.
There are many cases of foods that contain simple carbohydrates that are suitable for a healthful diet. For example, fruits and vegetables contain simple carbohydrates, but they are rich in micro-nutrients, such as vitamins and minerals, and they contain some dietary fiber.
Milk and milk products contain lactose, which is a type of simple carbohydrate. These foods do not contain fiber but are rich in protein, calcium, and vitamin D.
Simple carbohydrates to avoid are typically in processed foods or those with added sugar. Adding sugar to food increases its calorie content, without providing any additional nutrition.
Examples of such foods include:
- sugary drinks
- table sugar
- fruit juice concentrate
- products with added sugar, such as baked goods or some cereals
Whenever it is possible, people should try to stick to eating whole fruits rather than fruit juice. Whole fruits contain more dietary fiber and are a better option.
There may be some situations where these forms of less healthful, simple carbohydrates can be beneficial. For example, many sports drinks contain large amounts of added sugar. Manufacturers market these drinks as beverages for improving performance and enhancing rehydration.
However, the evidence for their effectiveness is lacking. A systematic review of 17 studies on the topic found no improvements in performance in half of the studies. In the other half, improvements ranged from 1–13%.
Sports drinks may be beneficial for improving performance, but the effect is likely to be small. It is unclear whether this possible benefit offsets the health consequences of having so much added sugar in a diet.
Complex carbohydrates found in whole foods tend to be highly nutritious.
For example, whole-grain foods contain a layer of bran and germ, which provide fiber, vitamin B and E, phytochemicals, and healthful fats.
They may also reduce the risk of several chronic health conditions, such as type 1 diabetes , cardiovascular disease, and several forms of cancer.
Examples of whole grains include:
- brown rice
- bulgur wheat
- wild rice
Refined grains are also complex carbohydrates but do not contain the bran and germ of the grain, and they have a lower nutritional value than whole-grain foods.
Examples of refined grains include:
- white flour
- degermed cornmeal
- white bread
- white rice
Vegetables, legumes, and nuts are also examples of highly nutritious sources of complex carbohydrates. It is easy to leave the skin on vegetables and fruit before eating, which will increase their nutritional value.