Sucrose, glucose, and fructose explained
Sucrose is another name for plain white table sugar. It’s made up of two other sugars: glucose and fructose.
Glucose, fructose, and sucrose all contain the same amount of energy per gram.
Each of these sugars occurs naturally in certain foods. But manufacturers also add them to many processed foods and drinks.
The main difference between these sugars is their structure, which affects how your body digests and absorbs them.
This distinction means that they may have different effects on your health.
Rather than focusing on which types of sugar to eat or avoid, you can make more of a difference to your health by checking for added sugars.
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What are the differences?
Sugars can be either monosaccharides and disaccharides.
"Monosaccharide" means "one saccharide," or sugar unit. These units are the building blocks of carbohydrates. Disaccharides have two monosaccharides joined together.
Your body digests and metabolizes these sugars differently.
Sucrose — or table sugar — is a disaccharide composed of one glucose and one fructose unit. Manufacturers create it by processing sugar cane and sugar beets.
Sucrose is probably the sugar that you come across most often. It naturally occurs in many fruits and vegetables.
Manufacturers also add it to foods and drinks like sodas, breakfast cereals, and ice cream.
Because sucrose is a disaccharide, your body has to break it down into monosaccharides before it’s absorbed into your bloodstream.
Glucose is a monosaccharide in grains, nuts, and vegetables. It also occurs in starchy foods like potatoes and rice.
However, glucose is also present in disaccharides, like sucrose or lactose, which is the sugar in milk.
Your body uses glucose as its main source of energy. On food labels, glucose sometimes appears as “dextrose.”
Dextrose has the same structure as glucose, and it’s common in food manufacturing. You might see it in ingredients lists for baked goods, corn syrup, and other processed foods.
When you eat foods containing glucose, your body will use what it needs and store the rest as glycogen in your liver or muscles.
The hormone insulin tightly controls glucose levels in your blood.
Like glucose, fructose is a monosaccharide. It occurs naturally in fruits, honey, and many root vegetables.
When manufacturers add fructose to products, you may see it as “high fructose corn syrup” on packaging. It tends to be in sauces, sugary drinks, fast food, and flavored yogurt.
Your liver needs to convert fructose into glucose before your body can use it as fuel.
Sucrose is a disaccharide — it’s composed of one unit of glucose and one of fructose. On their own, both glucose and fructose are monosaccharides.
Your body uses glucose as its main source of energy. It needs to convert other sugars into glucose before it can use them.
Absorption and digestion
Your body digests and absorbs different types of sugars in different ways. For instance, you absorb monosaccharides straight into your bloodstream.
But you need enzymes to break down disaccharides into monosaccharides before these get absorbed.
Your body must break down sucrose into glucose and fructose monosaccharides before you can absorb these sugars into your blood.
The process begins in your mouth, but most of the work occurs in your small intestine.
Your body doesn't have to break down glucose before it absorbs it.
This is why glucose can raise your blood sugar more quickly than other, more complex sugars.
Once glucose enters your blood, it triggers the release of insulin. This helps glucose move from your bloodstream into your cells. It reduces the level of glucose in your blood.
Because fructose is a monosaccharide like glucose, it’s absorbed directly into your bloodstream.
However, your body can’t use fructose as energy. As a result, your liver has to convert it into glucose. Because of this extra step, fructose doesn’t stimulate the release of insulin.
If you consume very large amounts of added fructose, it may cause health problems.
This may be because consuming too much fructose causes fat to build up in your liver.
However, scientists still don’t fully understand the links, and research is ongoing.
It’s important to know that eating fructose in its natural form, in fruits and vegetables, poses no health risks.
This is thanks to the other components of these plants: Their water and fiber cause you to absorb fructose into your blood at a slower rate.
Also, the wide range of health benefits associated with eating fruit and vegetables offset any harm that their fructose might cause.
You can absorb glucose and fructose straight into your bloodstream, but your body has to break down sucrose first.
Because you absorb glucose directly, it can raise your blood sugar level quickly. Your body can’t use fructose as energy, so after it’s absorbed, your liver has to convert it into glucose.
Added sugars and processed foods
Added sugars are any sugars that a manufacturer has added to their product.
On labels, added sucrose, fructose, and glucose can go by many names.
Look out for ingredients such as:
high fructose corn syrup
We’ve put together a more extensive list in our article on added sugars.
Where to find added sugars
Soda is one of the biggest sources of added sugar.
The American Heart Association explains that sweetened drinks make up almost half of the sources of added sugar in people’s diets. Sports drinks, flavored coffees, and sweet teas also fall into this category.
Because these drinks contain no fiber, you absorb the sugar into your bloodstream quickly.
Low-fat products also often contain added sugars. Manufacturers add sugars to replace the taste lost when they remove fat.
Health effects of added sugar
Research has also shown an association between eating lots of sugar and cardiometabolic diseases, such as:
In addition, research suggests that too much added sugar could have an unfavorable effect on your long-term mental health.
Which of these sugars is healthiest?
Overall, no type of sugar is the most or least healthy.
We typically eat sugar in meals and drinks, and these are what we should focus on.
If we’re singling out added sugars, fructose might have the most harmful effects, though scientists are still investigating.
It’s also worth noting that everyone handles sugar slightly differently. Some people might have a large blood sugar response to one type of food, while others might not.
ZOE runs the largest nutrition science study in the world. We know that our blood sugar rises after we eat certain foods and falls again afterward in a way that’s unique to each of us.
Using our at-home test, you can learn how different foods will affect your blood sugar and blood fat levels. You’ll also discover how healthy your gut is.
How to limit your added sugar intake
Limiting natural sugars (from fruits, vegetables, and other whole foods) isn’t necessary for most people.
Most of the health issues linked to eating too much sugar come from added sugars or “free sugars.”
“Free sugars” typically refers to added sugars plus the natural sugars in juiced or pureed fruit and veggies, though the definition can vary.
When you juice or puree these plants, it breaks down their structure, freeing the sugars from the plants’ cells. This makes it easier for your body to absorb the sugars.
No foods should be completely off-limits, but eating more whole foods and cutting back on ultra-processed foods is the best way to reduce your added sugar intake.
Because sugary drinks are such a common source of added sugar, reducing your intake of these might be a good place to start.
Another healthy habit is combining sugary foods with foods high in fiber, healthy fat, or protein.
This can slow the rate at which you absorb the sugar, reducing the risk of a large blood sugar rise.
Eating meals with higher amounts of fiber, protein, and non-sugary carbs also means you're less likely to have a significant blood sugar dip afterward. These dips can cause food cravings for some people.
But it’s worth noting that not everyone experiences blood sugar dips.
Our article on how to stop eating sugar has more detailed advice and information about reducing your sugar intake.
Experts agree: There’s no need for most people to limit their intake of sugar from natural sources, like fruits and vegetables.
Looking out for added and free sugars is the best way to reduce your sugar intake and support your health.
Overall, fructose might have the most harmful effects — when it’s an added sugar and you have large quantities.
Still, rather than focusing on which sugars are most healthy or unhealthy, it’s more useful to focus on the foods and drinks containing the sugar.
A healthy diet contains lots of whole foods, which slow your absorption of sugar. It’s also a good idea to keep an eye on how much added sugar is in the processed foods you’re consuming.
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