What is Fructose?

Highlights

  • Fructose is a type of sugar known as a monosaccharide.
  • Like other sugars, fructose provides four calories per gram.
  • Fructose is also known as “fruit sugar” because it primarily occurs naturally in many fruits. It also occurs naturally in other plant foods such as honey, sugar beets, sugar cane and vegetables.
  • Fructose is the sweetest naturally occurring carbohydrate and is 1.2–1.8 times sweeter than sucrose (table sugar).
  • Fructose metabolism does not require insulin and has a low impact on blood glucose levels.

There are many different types of sugars, some of which are more common than others. Fructose is a type of sugar known as a monosaccharide, or a “single” sugar, like glucose. Monosaccharides can bond together to form disaccharides, the most common of which is sucrose, or “table sugar.” Sucrose is 50% fructose and 50% glucose. Fructose and glucose have the same chemical formula (C6H12O6) but have different molecular structures, which makes fructose 1.2–1.8 times sweeter than sucrose. In fact, fructose is the sweetest naturally occurring carbohydrate. In nature, fructose is most often found as part of sucrose. Fructose is also found in plants as a monosaccharide, but never without the presence of other sugars.

Where does fructose come from?

Sometimes called “fruit sugar,” fructose is a naturally occurring sugar found primarily in fruits (such as apples, dates, figs, pears and prunes), but also in vegetables (such as artichokes, asparagus, mushrooms, onions and red peppers), honey, sugar beets and sugar cane. Pure fructose is produced commercially from corn or sucrose into a crystalline form for use as an ingredient in packaged foods and beverages. Although fructose is in high fructose corn syrup (a 55:45 mixture of the monosaccharides fructose and glucose), crystalline fructose should not be confused with high fructose corn syrup.

Is fructose a natural or added sugar?

Fructose can be a natural sugar or an added sugar, depending on its source. It is considered a natural sugar when we consume it directly from whole plant foods. It is considered an added sugar when we consume it from packaged foods and beverages to which fructose-containing sugars (such as crystalline fructose, high fructose corn syrup or sucrose) have been added during manufacturing.

While there is no recommendation established for fructose consumption, current dietary guidance recommends limiting the consumption of added sugars to less than 10% of total calories—in other words, less than 50 grams of added sugars if you consume 2,000 calories per day. About six in ten American adults eat more added sugars than is recommended.

How is fructose digested?

Most sugars are metabolized by the body in similar ways. Fructose, however, is handled somewhat differently than other sugars. This has led to some debate among nutrition scientists about fructose’s role in health. A 2016 review concluded that while fructose does not appear to have a unique impact on health, “fructose-containing sugars can lead to weight gain, increase in cardiometabolic risk factors and disease only if it provides the excess calories.”

Whether consumed from whole foods, high fructose corn syrup, sucrose or as an added ingredient, most of the fructose we consume is metabolized by the liver, where it is converted into energy sources for the body through a process that does not require insulin. Glucose, in contrast, is released into the blood stream for our tissues to use as energy with the help of insulin. Regardless of its source, fructose and other commonly consumed sugars provide about the same number of calories (four) per gram. Unlike other sugars, fructose does not require insulin to be absorbed and therefore has a low impact on blood glucose levels.

Some people have trouble absorbing fructose when eating it in large amounts and some are unable to absorb fructose at all. For affected individuals, it is recommended to monitor or limit fructose intake, and in the case of the rare genetic disorder called hereditary fructose intolerance (HFI), to avoid it entirely. About one in 20,000–30,000 people are born with HFI each year. Because individuals with HFI cannot metabolize fructose, foods and beverages containing fructose, sucrose or the sugar alcohol sorbitol must be excluded from their diet.

Why is fructose added to foods and beverages?

Most of the fructose we consume is in the form of sucrose and high fructose corn syrup. When added as an ingredient to packaged foods and beverages, the primary use for pure fructose is sweetness. Because its sweetness is detected and fades more quickly than sucrose, fructose can be used to minimize lingering sweetness in some products. Less fructose is needed to achieve the same sweetness as sucrose, and as such, reduced-calorie products sometimes contain pure fructose as an ingredient.

There are other reasons besides adding sweetness that fructose is used in foods. For example, fructose is one of the most soluble sugars, so it blends well in beverages. Fructose also is hygroscopic, which essentially means that it is good at absorbing water. In addition, fructose acts a humectant—a substance that is used to help retain moisture. All these properties can improve texture (e.g., frozen fruit) and extend the shelf-life (e.g., breads and bakery products) of foods.

To learn more about carbohydrates and sugars like fructose, watch this video.