Good sugar? Bad sugar? How well do you know this sweet-tasting substance?

Sugar does not have a good image. In doing so, it is not "bad" in itself. On the contrary, we even need it: "Humans need large quantities of energy to survive. Glucose (grape sugar) is primarily used as fuel. In carbohydrate metabolism, this simple sugar plays a central role for the brain and muscles," explains health and nutrition expert Hannah Frey (in German).

This is why the blood of healthy people also contains 60 to 140 mg of glucose per 100 ml. Without it, we wouldn't be able to breathe, walk, talk or think. "The brain alone needs 130 to 140 g of glucose a day, or 75 per cent of the total consumption of all the cells in the body," explains Frey. In stressful situations, the brain's sugar requirements can even soar to 95 per cent.

Because our thinking organ cannot store energy, it actively draws the glucose it needs from reserves in the blood, liver and muscles. This mechanism was discovered by Professor of Medicine Achim Peters in 1998. If the brain doesn't get what it needs, it shuts down after ten seconds and irreversible brain damage occurs after a few minutes.

But then, why is the World Health Organisation (WHO) recommending that we drastically reduce our sugar intake?

The answer is simple: in Western society, we tend to eat far more sugar than we need. The detailed, not-so-simple version follows here in nine points:

Fact 1: not all sugars are the same

Without studying chemistry, it's not so easy to get to grips with the subject of sugar. To the uninitiated, sugar is generally the white substance that trickles out of the sprinkler. Chemically speaking, it is sucrose, extracted from sugar beet and sugar cane. Sugar is a member of the carbohydrate class of substances known as saccharides. And they come in different forms:

According to the "Gesellschaft Deutscher Chemiker" (Society of German Chemists), it's important to know the following for your home use: monosaccharides are the simplest sugars. They are made up of just one sugar molecule. The most common simple sugars are glucose (grape sugar), fructose (fruit sugar) and ribose. Such monosaccharides are found naturally in fruit, vegetables and dairy products. But they are also added to many drinks, confectionery and finished products as refined (i.e. processed and isolated) sugar, which is cheap to produce, in order to sweeten and improve texture.

If two monosaccharides combine, the result is disaccharides (double sugars). These include table sugar (sucrose), which is made up of fructose and glucose, as well as lactose (milk sugar) and maltose (malt sugar). Double sugars are therefore found in all meals and products to which table sugar is added, or in foods such as yoghurt, cheese and ice cream.

Multiple sugars (oligosaccharides) are made up of several single and/or double sugar molecules. Raffinose and stachyose, found in legumes and some vegetables, are examples.

Multiple sugars (oligosaccharides) are made up of several single and/or double sugar molecules.

Finally, multiple sugars (polysaccharides) are made up of many linked single, double and/or multiple sugar molecules. They include starch and glycogen, which are found in foods of animal and plant origin, such as potatoes.

Fact 2: each sugar is processed differently

Your body does not react in the same way to each of these four types of sugar. The more complex the structure of a sugar, the weaker its influence on blood sugar levels. This is because all types of sugar must first be broken down into simple sugars before they can be absorbed into the bloodstream and provide energy.

While insulin levels rise rapidly after eating foods containing single or double sugars and then fall back just as quickly, so that we are soon hungry again, they rise only slowly after eating complex carbohydrates. Foods containing multiple sugars therefore satiate better and for longer.

"Generally speaking, carbohydrate intake through multiple sugars, especially starch, is to be preferred. Due to a sustained excessive intake of single and double sugars, which triggers a rapid insulin response in the body, when this process becomes chronic and blood sugar levels are persistently high, diseases such as diabetes appear," explain the experts at the expert portal for the chemical sector (in German).

Fact 3: not all sugars are "bad" in the same way

In its Guidelines, the WHO therefore advises covering a maximum of five to ten per cent of energy intake with free sugars. All single and double sugars that are artificially added to the diet are considered to be "bad" free sugars. These are mainly glucose, fructose and sucrose. The natural sugar content of honey, syrups, fruit juices and fruit juice concentrates is also counted as free sugar.

Free sugars don't just make foods high in calories, which is what is associated with the rise in obesity in industrialised countries. Free sugar, which is mostly found in the form of refined and processed sugar, also contains few minerals, so there are no health benefits. Quite the opposite, in fact. The WHO warns that, in addition to type 2 diabetes, excessive consumption can lead to heart disease, tooth decay and inflammation.

Added fructose is considered particularly bad. In fact, it is transformed into fat in the liver. Fructose is therefore suspected of contributing to fatty liver and, in large quantities, of promoting obesity and diabetes. This is why the German Federal Institute for Risk Assessment (BfR) advises against products with a high fructose content, such as shop-bought fruit juices, especially as these lack the fibre, vitamins and other substances still present in fresh fruit.

Speaking of fruit, sugar is naturally present in fresh fruit and vegetables as well as milk. Their fructose or lactose doesn't count when it comes to daily sugar intake. In fact, researchers have so far been unable to demonstrate any negative effects for their consumption, as sugar is also absorbed with other nutrients and dietary fibres in food.

Fact 4: you're (probably) eating too much sugar

According to estimates by the Federal Office for Food Safety and Veterinary Affairs (FOSV), the Swiss consume around 110g of free sugar a day

That's 20 times more than 150 years ago, when sugar was still a luxury, and up to four times more than recommended by the World Health Organisation. To stay within the recommended limits, you should reduce your daily intake to around 25-50g, or a maximum of 5-10 teaspoons of free sugar a day.

Not easy, because according to the WHO, a single teaspoon of ketchup already contains around 4 grams of free sugar, and a can of soda even contains 40 grams or 10 teaspoons, which means your daily sugar limit has already been reached.

Fact 5: sugar has many names

Reducing your sugar intake is therefore a real challenge. The simplest is still table sugar: when you cook, bake or sweeten coffee, you're finally in control of the sugar sprinkler. But it's processed foods that account for the lion's share of daily sugar consumption. And this is where manufacturers often make it really difficult for us by imposing restrictions. Indeed, even after studying the list of ingredients, we are often unaware that a food contains (a lot of) sugar. This is because there are more than 50 names (in German) for sugar to disguise the actual sugar content.

The most common aliases are glucose (grape sugar), fructose (fruit sugar) and galactose, sucrose (table sugar), lactose (milk sugar) and maltose, raffinose and stachyose, as well as starch and glycogen. But we also often find names such as dextrose, caramel syrup, malt (barley) extract, fructose-glucose and starch syrup, (skimmed) milk powder or maltodextrin.

In addition, sugar can also be introduced into foods via a sweetening ingredient, for example in the form of honey, date powder, agave syrup or fruit purees.

Fact 6: the ingredients list is often misleading

Even if you know all the alternative names for sugar, it's often difficult to estimate the sugar content of a food. This is because all types of sugar are listed individually in the ingredients list. As a result, the word sugar and its other names tend to take a back seat when you're dealing with a sugar bomb. The total sugar content can usually only be deciphered with the help of the nutritional facts table, explains the German consumer association.

The difference in the definition of sugar in the list of ingredients and in the nutrition label can, however, lead to confusion. In fact, in the nutritional facts table, all the monosaccharides and disaccharides contained in the product are grouped together under the term sugar. This means that the sugar naturally contained in milk or fruit is also included. On the other hand, glucose syrup should not be listed as a sugar in the nutritional information if it contains more tri- and polysaccharides (three or more sugars) than di- or monosaccharides (two or just one sugar). At the end of the day, it is still sugar.

The difference between grams of sugar and grams of carbohydrates is an indication that (too much) sugar is hiding in a product. If these indications are markedly different, you should be wary of sugary products.

Fact 7: going completely sugar-free is difficult to achieve

A diet without any form of sugar therefore becomes really difficult. The "no sugar" instruction significantly reduces your basket. A Canadian study (in English) revealed that two-thirds of pre-packaged foods sold in American and Canadian supermarkets contain at least one form of added sugar. Studies are lacking in our region, but the result would probably be similar. Indeed, even foods that manufacturers describe as sugar-free can still contain up to 0.5g of sugar per 100g or 100ml, according to the German Food Association.

But despite all these obstacles, it is of course possible to limit your sugar intake. Hannah Frey has written several guides on the subject, and bookshops and the internet are full of other advice aimed at getting the body to make most of its own fuel instead of drawing it from single and double sugars.

"To do this, the body breaks down glucose in the intestine from polysaccharides (e.g. starch), found for example in vegetables, cereals or even pseudo-cereals such as amaranth. Even fats and proteins can be converted into energy by the body, albeit in a roundabout way," explains expert Hanna Frey.So we still eat sugar, but in the form of complex carbohydrates.

Fact 8: a completely sugar-free diet can harm you

While it makes good health sense to reduce free sugar, as recommended by the WHO, it's not advisable to give up all sugar altogether either. In fact, according to a list drawn up by the AOK health fund, only a few foods are truly sugar-free: meat and fish, for example, olive oil, black tea and coffee.

"For a completely sugar-free diet, you would therefore have to cut out a lot of healthy things like fruit or vegetables," explains nutritionist Uwe Knop. Apart from the fact that this would deprive you of vitamins, fibre and micronutrients, your diet would be rather unbalanced, if not probably harmful.

Caution is also advised when replacing sugar-containing products with substitutes such as aspartame. For the Canadian Medical Association Journal, researchers have summarised existing studies on artificial sweeteners. Their conclusion: in the long term, you end up with exactly what you wanted to avoid by giving up sugar. The risk of obesity, type 2 diabetes, hypertension or heart disease increases.

The reason: low-calorie or no-calorie sweeteners are suspected of having a negative influence on metabolism, intestinal bacteria and appetite. In fact, the sweet taste suggests to the body a high energy intake, which is not the case.

Fact 9: eating intuitively helps you control your sugar intake

Many specialists follow the WHO recommendation to reduce free sugar consumption by a third or, better still, by half. However, as with all foods, the amount of sugar that is (still) acceptable also depends on the individual, their genetics and chronobiology, lifestyle, metabolism and energy consumption, explains Uwe Knop. People who lead a healthy lifestyle and take regular exercise quickly burn off the sugar in a bar of chocolate. On the other hand, if you stay glued to the sofa after a meal too rich in sugar, the sugar accumulates as fat in your organs and muscles.

And as it can be difficult to determine the sugar content of processed foods and reduce it to grams and teaspoons, the nutrition expert recommends trusting your body, eating when you're really hungry and choosing what's good and tolerated, whether it's chocolate or salad. This principle is called intuitive eating (in German) and has been shown in numerous studies to have positive effects on physical and mental health. The desire to eat foods high in sugar or fat should thus diminish on its own.

At the same time, you learn to perceive and understand the signals your body sends you asking for healthy foods. "Eating intuitively therefore also makes it possible to avoid an extremely unbalanced diet, or even one based exclusively on sugar, which would of course be dangerous for your health. "