Carbohydrates
The primary energy source for the human body
Carbohydrates are a large class of nutrients, including sugars, starches, and fibers, that function as the body's primary energy source.​
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Carbohydrates are a large class of nutrients, including sugars, starches, and fibers, that function as the body's primary energy source.
Carbohydrates
Sugars, starches, and fibers all belong to carbohydrates. Carbohydrates are the energy-yielding nutrient. All carbohydrates are made of the same three elements: carbon, hydrogen, and oxygen.
Grains, like oats and rice, are rich in carbohydrates. When grains such as wheat are ground, it produces flour to bake bread, tortillas, crackers, cookies, and cakes.
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Carbohydrate is the primary energy source for most of us. Carbohydrates produce energy for our bodies, and carbohydrates can spare protein for the body’s use. Carbohydrates can also assist in lipid/fat metabolism.
Carbohydrates from Plant-based Foods
Carbohydrates are the ideal nutrient to meet your body's nutritional needs. Carbohydrates nourish the brain and nervous system, provide energy to all your cells within proper caloric limits, and help keep the body fit.
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Specifically, digestible carbohydrates provide bulk in foods, vitamins, and minerals, while indigestible carbohydrates provide good fiber and other health benefits.
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Plants harness the sun's energy to synthesize glucose from carbon dioxide in the air and water. Plants convert the energy in sunlight to chemical energy in glucose. This is called photosynthesis.
Glucose is a fast-releasing carbohydrate that can be directly used for energy in plants and humans. Plants use glucose to make other larger, more slow-releasing carbohydrates, starches, and fibers. When we eat plant foods, we harvest the energy of glucose, starches, fibers, and other phytonutrients from plant-based foods to support our life processes.
The Whole Nutrient Package
In choosing dietary sources of carbohydrates, the best choices are those that are nutrient-dense, meaning they contain more essential nutrients per kilocalorie of energy. Nutrient-dense carbohydrates are minimally processed, including whole-grain bread and cereals, low-fat dairy products, fruits, vegetables, and beans.
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In contrast, empty-calorie carbohydrate foods are highly processed and often contain added sugars and saturated fats. Empty-calorie carbohydrates include soft drinks, cakes, cookies, and candy. They are sometimes called ‘bad carbohydrates,’ as they have no other significant nutrients except added sugar.
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Reference: Part D. Section 5: Carbohydrates. In Report of the DGAC on the Dietary Guidelines for Americans, US Department of Agriculture. 2010.
Calories of Carbohydrates, Sugar, and Starch
Whether from sugars or starch, a single gram of carbohydrate fuels your body with the same amount of energy, four kilocalories per gram of sugar or starches. By comparison, protein supplies four kilocalories per gram, and fat provides nine kilocalories per gram.
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Fiber fermentation in the gut is estimated to provide two kilocalories per gram of dietary fiber. However, since not all fiber is fermentable, calculating fiber's energy value poses problems and can lead to calorie miscalculations.
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The bottom line of carbohydrates is: For your health, make nutrient-rich carbohydrate foods your body's primary energy source.
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Reference: Institute of Medicine 2005. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press. https://doi.org/10.17226/10490.