Sep 14, 2020
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Sweet theme. What is the difference between sugar, glucose, fructose and other “ozes”?

We hear constantly that sugar is bad. From it you get fat, your teeth deteriorate, your blood sugar rises ... Or does glucose rise? Doctors say so and so. Where is the truth? And what is this glucose - sugar or not? There are also some fructose, sucrose, lactose ...

Let's continue: there is also dextrose, galactose, maltose, grape, milk and fruit sugars. How to understand them? What is the most harmful thing? And maybe something useful? For example, fructose is sold in health food departments and is also recommended for diabetics. So it is good for you?

Don't wander in three pines

“Almost all sugars that we consume with food and that are important for our health are based on just three bricks", - explains candidate of chemical sciences and popularizer of science Petr Obraztsov... - These are simple sugars - glucose, fructose and galactose. More and more complex sugars are built from them"...

Glucose - the most famous of them, its other names - grape sugar or dextrose. Grape - because there is a lot of it in these berries. In general, it is found in almost all fruits, berries and honey; manufacturers often add it to products. In the pharmacy, you can buy glucose tablets, which are sold for children as a source of energy (sometimes they call this sugar the rarer word "dextrose"). It is glucose that is determined in the blood. And even when a doctor tells a patient that he has a high sugar, he always means that it is she who is increased. Sugar here acts as a synonym for glucose.

Fructose Is the other most common simple sugar. From the name it is clear that there is a lot of it in fruits, but even more in honey, in berries - less.

Galactose (milk sugar, from ancient Greek "galactose" - milk) is less common in nature, in its pure form in a very small amount (fractions of a percent) in some vegetables and fruits. But we mainly get it in the form of another milk sugar - lactose (its name comes from the Latin "lactis" - milk).

Agree, there is a reason to get confused: two different sugars are called the same milk and at the same time have their own different names. How is this possible? To figure it out, it's time to move on to more complex sugars, consisting of two "building blocks". Therefore, they are called disaccharides: the particle "di" means two.

Buildings from "bricks"

Lactose is a disaccharide composed of galactose and glucose. It tastes almost not sweet, and therefore the milk is also not sweet, although each glass contains about 2 spoons of lactose sugar (8-10 g). In the digestive tract, it breaks down into the original "bricks" - galactose and lactose. And already they are absorbed into the blood. Disaccharides are not absorbed. If a person does not have the enzyme lactase that breaks down this milk sugar, it begins to ferment in the intestines, causing flatulence (profuse gas formation) and diarrhea. This is lactose intolerance.

Sucrose is the best known sugar. Even if this chemical name is unknown to you, you know it perfectly and consume it almost every day. This is the same "white death", which is sold in the form of sand or pieces of refined sugar and which is added to tea, coffee, porridge, and is used in cooking. We just call it sugar. This is a common name. The "oza" particle at the end of sucrose in the language of chemistry means that this substance belongs to sugars. Remember the names of other sugars: glucose, fructose ... It is from these two “building blocks that ordinary sugar is composed, and into which it breaks down during digestion.

Maltose is a less familiar disaccharide. It consists of two identical glucose “bricks”. It got its name from barley malt (malt), which contains the most of it. Fans of real Scotch whiskey probably already think that this drink contains the most maltose, because Single malt whiskey is made only from such malt. In fact, neither the barrel nor the bottle of maltose reaches the barrel. A significant part of it decomposes during fermentation, and the remains go to waste during distillation. But in beer it is (it is not distilled). And most of all we consume maltose in the composition of beer and products with the addition of malt (most often these are bakery products).

There are also polysaccharides - long chains of glucose "bricks", branched, entangled. This starch is found in plants. Animal starch synthesized in the liver is called glycogen.

And if these "bricks" of glucose are connected in such a special way that our enzymes cannot separate (digest) them, then this is already fiber (cellulose) - dense dietary fiber. They are the membranes of plant cells that play a useful role in digestion. They trap some toxins and harmful substances, and without them we would suffer from severe constipation.

Table. Glycemic index and sweetness of various sugars

Sugar name

Glycemic index (GI)






one hundred *


Sucrose (table sugar)


one hundred **










Note: * GI glucose is taken as 100, all others are estimated in comparison with it

** The sweetness of sucrose is taken as 100, and the sweetness of the remaining sugars is compared with this standard

Not all sugars are sweet

All of these characteristics of sugars affect their health effects. One of the main properties - it is their ability to increase blood glucose (see table). The more this happens, the higher the risk of developing obesity, and then type 2 diabetes. This ability is characterized by the glycemic index (GI) - the higher it is, the worse. It is highest in glucose (100) and maltose (105). With glucose, everything is clear, almost all of the eaten glucose is absorbed into the blood and works to increase it. Maltose has a slightly higher GI, but not critically: each molecule of this sugar breaks down into two "bricks" of glucose, which greatly increases its concentration in the blood. This, by the way, must be taken into account when drinking beer: a decent amount of maltose is masked by a bitter taste - being unsweetened, this sugar does not interrupt the bitterness. And if instead of maltose there was sucrose or fructose, the beer would have a strong sweet taste.

Next comes our regular sugar (sucrose), it has a significantly lower GI, but it's still quite high (65). And this is also understandable: sugar breaks down into glucose and fructose. The first immediately increases blood glucose, the second indirectly. Only part of the fructose in the body is converted to glucose, helping to increase its concentration in the blood.

By the way, this property of fructose to increase sugar less and not require insulin for its assimilation was used to prescribe it to diabetics as an alternative to ordinary sugar. But in recent years, doctors have accumulated a lot of dirt on fructose, and now they are trying to reduce its consumption. However, it comes with a creak, in the food industry it is still used very much and continues to be sold in the departments of dietary nutrition.

Since lactose breaks down only one molecule of glucose, it does not greatly increase blood levels. Galactose, the second “building block” of lactose breakdown, does little to increase blood glucose. But while savory, it isn't nearly as interesting as fructose to use in place of sugar. The latter is generally the sweetest sugar, it is 1.7 sweeter than sucrose (see table).

Galactose itself is important for young children, it is abundant in breast milk. But there is more and more evidence that it is harmful afterwards. This sugar accelerates the aging of the body, and it is even used in an experiment to make animals age faster. Therefore, the theory that milk is not useful for adults is gaining new evidence. Instead, it is better to consume fermented milk products, in which a significant part of the lactose is destroyed during souring.

There are contraindications. Be sure to consult your doctor.

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