Carbohydrates are the main source of energy for the body. They are the sugars, starches, and dietary fiber that occur in plant foods and dairy products.
Carbohydrates are mainly found in plant foods. They also occur in dairy products in the form of a milk sugar called lactose. Foods high in carbohydrates include bread, pasta, beans, potatoes, rice, and cereals.
Carbohydrates play several roles in living organisms, including providing energy.
Byproducts of carbohydrates are involved in the immune system, the development of disease, blood clotting, and reproduction.
This article looks at types of carbohydrates, nutrition, and their effects on health. We also look at the relationship between carbohydrates and diabetes.
What are carbohydrates?
Carbohydrates, also known as saccharides or carbs, provide energy for the body. Each gram of carbohydrates provides 4 calories.
The body breaks carbohydrates down into glucose, which is the primary energy source for the brain and muscles.
Carbohydrates are one of three macronutrients, which are nutrients that the body needs in larger amounts.
The other macronutrients are protein and fats. Proteins provide 4 calories per gram, and fats provide 9 calories per gram.
Nutrition
It’s generally recommended that people consume between 45-65% of their total calories in the form of carbohydrates per day. However, carbohydrate needs depend on many factors, including body size, activity levels, and blood sugar control.
The Food and Drug Administration (FDA) recommend that people get 275 g of carbohydrate each day in a 2,000-calorie diet. This includes dietary fiber, total sugars, and added sugars, which are listed on food labels.
Carbohydrates in foods occur in various forms, including the following:
- Dietary fiber, a type of carbohydrate that the body cannot easily digest. It occurs naturally in fruits, vegetables, nuts, seeds, beans, and whole grains.
- Total sugars, which include sugars that occur naturally in foods, such as dairy products, as well as added sugars, which are common in baked goods, sweets, and desserts. The body very easily digests and absorbs sugars.
- Sugar alcohols, a type of carbohydrate that the body does not fully absorb. They have a sweet taste and fewer calories than sugar. Sugar alcohols are added to foods as reduced-calorie sweeteners, such as in chewing gum, baked goods, and sweets.
Dietary fiber helps promote regular bowel movements, lowers blood sugar and cholesterol, and may help reduce a person’s calorie intake. The FDA recommend that people get 28 grams (g) of dietary fiber per day in a 2,000-calorie diet.
Most people in the United States exceed the recommended daily limits for added sugar. This can increase a person’s risk of developing cardiovascular disease and dental cavities.
The Dietary Guidelines for Americans 2015–2020Trusted Source recommend that people get less than 10% of their total daily calories from added sugars, which means less than 50 g of added sugars each day.
However, limiting added sugar as much as possible is best for overall health. The American Heart AssociationTrusted Source recommend that women limit added sugar to less than 6 teaspoons (25 g) per day and men limit their intake to less than 9 teaspoons (36 g) per day.
Chemistry
The chemical structures of carbohydrates contain carbon, hydrogen, and oxygen atoms. Two basic compounds make up carbohydrates: Aldehydes, which are double-bonded carbon and oxygen atoms, plus a hydrogen atom, and ketones, which are double-bonded carbon and oxygen atoms, plus two additional carbon atoms.
Carbohydrates can combine to form polymers, or chains, to create different types of carbohydrates. Carbohydrate can be monosaccharides, disaccharides, or polysaccharides.
Monosaccharides
Monosaccharides are single units of sugar. Examples include:
- glucose, the body’s main source of energy
- galactose, which is most readily available in milk and dairy products
- fructose, which mostly occurs in fruits and vegetables
Disaccharides
Disaccharides are two sugar molecules joined together. Examples include:
- lactose, found in milk, which is made up of glucose and galactose
- sucrose, or table sugar, which is made up of glucose and fructose
Polysaccharides
Polysaccharides are chains of many sugars. They can consist of hundreds or thousands of monosaccharides. Polysaccharides act as food stores for plants and animals. Examples include:
- glycogen, which stores energy in the liver and muscles
- starches, which are abundant in potatoes, rice, and wheat
- cellulose, one of the main structural components of plants
Simple and complex carbohydrates
Monosaccharides and disaccharides are simple carbohydrates, and polysaccharides are complex carbohydrates.
Simple carbohydrates are sugars. They consist of just one or two molecules. They provide a rapid source of energy, but the person soon feels hungry again. Examples include white bread, sugars, and candies.
Complex carbohydrates consist of long chains of sugar molecules. This includes whole grains and foods that contain fiber. Examples include fruits, vegetables, beans, and whole grain pasta.
Complex carbohydrates make a person feel full for longer and have more health benefits than simple carbohydrates, as they contain more vitamins, minerals, and fiber.
Should I try a high or low carb diet?
In a typical diet, carbohydrates are the main energy source for the body. The body uses them as fuel for the cells.
Many people have turned to low carb diets, such as the keto diet, for their potential health benefits and weight loss. However, some types of carbohydrates – including whole grains and dietary fiber – have substantial health benefits.
In fact, according to the Physicians Committee for Responsible Medicine, those who eat the most carbohydrates – especially from natural sources such as beans, whole grains, and vegetables — have a lower risk for obesity, type 2 diabetes, and heart disease.
Other types of carbohydrates, including simple carbohydrates such as white bread, have much lower nutritional value.
Added sugars are a type of carbohydrate that can have adverse health effects. Eating large amounts of foods that contain added sugars can contribute to obesity, type 2 diabetes, and cardiovascular disease.
When making dietary changes, it is important to aim for a healthful diet that contains the range of nutrients that the body needs.
Carbohydrates and obesity
Some argue that the global rise in obesity is linked to a high intake of carbs. However, a number of factors contribute to rising obesity rates, includingTrusted Source:
- lower physical activity levels
- greater availability of ultraprocessed food or “junk food”
- a lack of access to affordable fresh produce
- oversized portions, which increase a person’s calorie intake
- fewer hours of sleep
- genetic factors
- stress and emotional factors
What about diet foods?
Many manufacturers promote low carb diets to sell weight loss products, including nutritional bars and powders.
These products are not often healthful as many contain colorings, artificial sweeteners, emulsifiers, and other additives and are typically low in vitamins, minerals, and antioxidants, making them similar to junk food.
