If you’re trying to cut back on sugar, you may wonder whether the type of sugar matters.
Sucrose, glucose and fructose are three types of sugar that contain the same number of calories gram for gram.
They’re all found naturally in fruits, vegetables, dairy products and grains but also added to many processed foods.
However, they differ in their chemical structures, the way your body digests and metabolizes them and how they affect your health.
This article examines the main differences between sucrose, glucose and fructose and why they matter.
Sucrose Is Made up of Glucose and Fructose
Sucrose is the scientific name for table sugar.
Sugars are categorized as monosaccharides or disaccharides.
Disaccharides are made up of two, linked monosaccharides and broken back down into the latter during digestion (1).
Sucrose is a disaccharide consisting of one glucose and one fructose molecule, or 50% glucose and 50% fructose.
It’s a naturally occurring carbohydrate found in many fruits, vegetables and grains, but it’s also added to many processed foods, such as candy, ice cream, breakfast cereals, canned foods, soda and other sweetened beverages.
Table sugar and the sucrose found in processed foods are commonly extracted from sugar cane or sugar beets.
Sucrose tastes less sweet than fructose but sweeter than glucose (2).
Glucose is a simple sugar or monosaccharide. It’s your body’s preferred carb-based energy source (1).
Monosaccharides are made up of one single unit of sugar and thus cannot be broken down into simpler compounds.
They’re the building blocks of carbohydrates.
In foods, glucose is most commonly bound to another simple sugar to form either polysaccharide starches or disaccharides, such as sucrose and lactose (1).
It’s often added to processed foods in the form of dextrose, which is extracted from cornstarch.
Glucose is less sweet than fructose and sucrose (2).
Fructose, or “fruit sugar,” is a monosaccharide like glucose (1).
It’s naturally found in fruit, honey, agave and most root vegetables. Moreover, it’s commonly added to processed foods in the form of high-fructose corn syrup.
Fructose is sourced from sugar cane, sugar beets and corn. High-fructose corn syrup is made from cornstarch and contains more fructose than glucose, compared to regular corn syrup (3).
Of the three sugars, fructose has the sweetest taste but least impact on your blood sugar (2).
They’re Digested and Absorbed Differently
Your body digests and absorbs monosaccharides and disaccharides differently.
Since monosaccharides are already in their simplest form, they don’t need to be broken down before your body can use them. They’re absorbed directly into your bloodstream, primarily in your small intestine (4).
On the other hand, disaccharides like sucrose must be broken down into simple sugars before they can be absorbed.
Once the sugars are in their simplest form, they’re metabolized differently.
Glucose Absorption and Use
It raises blood sugar more quickly than other sugars, which stimulates the release of insulin (6).
Insulin is needed for glucose to enter your cells (7).
Your body tightly controls your blood sugar levels. When they get too low, glycogen is broken down into glucose and released into your blood to be used for energy (9).
If glucose is unavailable, your liver can make this type of sugar from other fuel sources (9).
Fructose Absorption and Use
However, even though fructose doesn’t raise your blood sugar right away, it may have more long-term negative effects.
Your liver has to convert fructose into glucose before your body can use it for energy.
If you eat more fructose than your liver can handle, the excess is turned into cholesterol and triglycerides (11).
This may have negative health effects such as obesity, fatty liver disease and high cholesterol.
Sucrose Absorption and Use
Since sucrose is a saccharine, it must be broken down before your body can use it.
Enzymes in your mouth partially break down sucrose into glucose and fructose, and acid in your stomach breaks it down further. However, the majority of sugar digestion happens in the small intestine (4).
The enzyme sucrase, which is made by the lining of your small intestine, splits sucrose into glucose and fructose. They are then absorbed into your bloodstream as described above (4).
The presence of glucose increases the amount of fructose that is absorbed and also stimulates the release of insulin. This means that more fructose is used to create fat, compared to when this type of sugar is eaten alone (11).
Therefore, eating fructose and glucose together may harm your health more than eating them separately. This may explain why added sugars like high-fructose corn syrup are linked to various health issues.
Fructose May Be the Worst for Health
Your body converts fructose to glucose in the liver to use it for energy. Excess fructose places a burden on your liver, which may lead to a series of metabolic problems (11).
Several studies have demonstrated the harmful effects of high fructose consumption. These include insulin resistance, type 2 diabetes, obesity, fatty liver disease and metabolic syndrome (12, 13, 14).
In one 10-week study, people who drank fructose-sweetened beverages had an 8.6% increase in belly fat, compared to 4.8% in those who drank glucose-sweetened drinks (14).
Another study found that while all added sugars can increase your risk of type 2 diabetes and obesity, fructose may be the most harmful (15).
Since fructose is metabolized in your liver like alcohol, some evidence suggests that it may be similarly addictive. One study found that it activates the reward pathway in your brain, which may lead to increased sugar cravings (18, 19).
You Should Limit Your Added Sugar Intake
There is no need to avoid sugars that are naturally found in whole foods, such as fruits, vegetables and dairy products. These foods also contain nutrients, fiber and water, which counter any of their negative effects.
The harmful health effects associated with sugar consumption are due to the high amount of added sugar in the typical Western diet.
A survey of over 15,000 Americans found that the average person consumed 82 grams of added sugars per day, or approximately 16% of their total calories — far more than the daily recommendation (20).
The World Health Organization recommends limiting added sugars to 5–10% of your daily calorie consumption. In other words, if you’re eating 2,000 calories per day, keep added sugars to less than 25–50 grams (21).
To put that into perspective, one 12-ounce (355 ml) can of soda contains about 30 grams of added sugar, which is enough to push you over your daily limit (22).
What’s more, sugars are not only added to foods that are obviously sweet like sodas, ice cream and candy, but also to foods you wouldn’t necessarily expect, such as condiments, sauces and frozen foods.
When buying processed foods, always read the ingredient list carefully to look for hidden sugars. Keep in mind that sugar can be listed by over 50 different names.
The most effective way to reduce your sugar intake is to eat mostly whole and unprocessed foods.
The Bottom Line
Glucose and fructose are simple sugars or Saccharomyces.
Your body can absorb them more easily than the saccharine sucrose, which must be broken down first.
Fructose may have the most negative health effects, but experts agree that you should limit your intake of added sugar, regardless of the type.
However, there is no need to limit the sugars found naturally in fruits and vegetables.
To ensure a healthy diet, eat whole foods whenever possible and save added sugars for the occasional special treat.