How Do Vegetables Give You Energy?

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Vegetables have a host of health benefits. High in vitamins, minerals and fiber, they are critical to supporting optimal health. Although low in calories relative to other foods, vegetables contain a high percentage of carbohydrates, your body’s primary energy source.

Energy in Food

The energy content of food is calculated from the heat it releases. Scientists measure this value using a calorimeter, and the energy a food generates is expressed in kilocalories, or calories. The three main forms of calories are fat, protein and carbohydrate. Per gram, fat has more than twice the calories as carbohydrate, yet your body uses carbohydrates for energy first, storing fat for later use, according to the textbook “Biochemistry.”

Calories in Vegetables

Like most foods, vegetables contain a mixture of the three major calorie types. However, unlike animal products, such as meat and cheese, which derive a large portion of their calories from fat and protein, most vegetables are made up of mostly carbohydrate. Starchier vegetables, including potatoes and squash, contain more carbohydrate per serving than green vegetables, which are higher in protein.

Carbohydrates in Vegetables

Carbohydrates are classified by the sugars they contain. Simple sugars, such as glucose and fructose, are sweet tasting, as are disaccharides. These sugar pairs include sucrose, or table sugar. Sucrose consists of equal parts glucose and fructose. Longer chains of sugars are called polysaccharides, or starch. In contrast to simple sugars, starch does not have a sweet taste. The carbohydrates in most vegetables consist of glucose, fructose and sucrose, while potatoes and squash are higher in starch.

How Carbohydrates Provide Energy

The fructose and glucose in vegetables are free-form, and they do not require the work of digestive enzymes to break them down. Therefore, they rapidly enter your bloodstream, where they travel to the cells of your body for use as energy. By contrast, starchier vegetables require an abundance of the digestive enzyme amylase to break them down, in addition to other enzymes. Consequently, the energy potatoes provide may not be as immediate as that offered by, say, carrots, but the slower-digested starch provides sustained energy levels.