What is sugar?

Sugar is the name for a group of simple carbohydrates that taste sweet and provide the body with readily available energy . Chemically speaking, they are compounds of carbon, hydrogen, and oxygen that are easily converted by the body into glucose – the main energy source for cells, brain, and muscles.

In nutrition, a distinction is made between natural sugars , which occur in fruits, milk or vegetables, and added sugar , which is added to foods during production or preparation (e.g. in sweets, pastries or soft drinks).

Sugar provides 4 kcal (17 kJ) per gram , but contains no vitamins, minerals or fiber – which is why it is considered an “empty calorie” when consumed in large quantities.

Types of sugar

Sugar is classified into different groups according to its chemical structure:

1. Monosaccharides (simple sugars):

  • Glucose (dextrose): the most important energy source for the body.

  • Fructose (fruit sugar): is found in fruit, honey and some vegetables.

  • Galactose: a component of milk sugar (lactose).

2. Disaccharides (double sugars):

  • Sucrose (table sugar): consists of glucose and fructose; the most common added sugar.

  • Lactose (milk sugar): Glucose + Galactose; a natural component of milk.

  • Maltose (malt sugar): is produced during the breakdown of starch.

3. Oligo- and polysaccharides (complex sugars):
These consist of many simple sugar molecules and are classified as complex carbohydrates (e.g. starch).

How does sugar affect the body?

1. Fast energy source:
Sugar is rapidly absorbed in the small intestine after consumption and enters the bloodstream as glucose . Blood sugar levels rise, and the pancreas releases insulin to transport the glucose into the cells – where it is used directly for energy production.

2. Brain function:
The brain is particularly dependent on glucose. Short-term sugar consumption can improve concentration and reaction time – however, too much sugar can have the opposite effect, such as low energy and restlessness.

3. Influence on insulin and energy balance:
Frequent blood sugar spikes caused by excessive sugar consumption lead to insulin fluctuations , which can strain the metabolism and trigger cravings. In the long term, this can lead to insulin resistance , weight gain, and metabolic disorders.

4. Mood and reward:
Sugar activates the brain's reward system by stimulating the release of dopamine – similar to other stimulants. This explains why sugar makes you feel "happy" in the short term, but can also quickly lead to addiction .

Natural vs. added sugar

  • Natural sugars: occur in foods such as fruits, milk, and vegetables, where they are accompanied by fiber, water, vitamins, and minerals. This combination slows down absorption and has a positive effect on health.

  • Added sugar: is industrially processed in foods (e.g., table sugar, glucose syrup, fructose, maltodextrin) and provides only energy, but no nutrients.

Benefits (in moderate amounts)

  • Fast energy source for brain and muscles

  • Supports performance during intense physical activity

  • Can improve concentration and mood in the short term

  • It also provides vitamins and antioxidants in its natural form (e.g., fruit).

Risks of excessive sugar consumption

Consistently high sugar consumption is associated with numerous health problems, including:

  • Weight gain and obesity

  • Tooth decay caused by bacterial sugar decomposition in the mouth

  • Insulin resistance and type 2 diabetes

  • Fatty liver disease (non-alcoholic fatty liver disease)

  • Inflammatory processes and increased oxidative stress

  • Fluctuating energy and blood sugar levels

  • Increased risk of cardiovascular disease

Recommendations of the nutrition societies

The World Health Organization (WHO) recommends that a maximum of 10% of daily energy intake should come from added sugars – ideally less than 5% .

This is approximately equivalent to:

  • 25–50 g of sugar per day (6–12 teaspoons) for adults.

Sugar can hide behind many names, e.g. glucose syrup, dextrose, sucrose, maltose, invert sugar, fructose syrup – therefore it is worth taking a look at the ingredient list.

Conclusion

Sugar is a natural part of our diet and provides quick energy – in moderate amounts, it's perfectly safe. Problems arise with excessive consumption of added sugar , such as that found in soft drinks, sweets, and processed foods. Being mindful of sugar consumption means favoring natural sources like fruit and reducing industrially added sugar. This helps keep blood sugar levels stable, ensures a steady supply of energy, and protects long-term health.

Sources

  1. World Health Organization (WHO). (2015): Guideline: Sugar intake for adults and children.

  2. German Nutrition Society (DGE). (2020): Sugar and dental health – DGE recommendations.

  3. Lustig RH, Schmidt LA, Brindis CD. (2012): Public health: The toxic truth about sugar. Nature , 482(7383), 27–29.

  4. Te Morenga L, Mallard S, Mann J. (2013): Dietary sugars and body weight: systematic review and meta-analyses. BMJ , 346, e7492.