What is sugar?

Sugar is the name for a group of simple carbohydrates that taste sweet and provide the body with quickly available energy. Chemically, these are compounds of carbon, hydrogen, and oxygen that the body can easily convert into glucose, the main source of energy for cells, the brain, and muscles.

In nutrition, a distinction is made between natural sugars, found in fruit, milk, or vegetables, and added sugar, which is added to foods during manufacturing or preparation (e.g., in sweets, baked goods, 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 amounts.

Types of sugar

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

1. Monosaccharides (simple sugars):

  • Glucose (grape sugar): the body’s most important source of energy.

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

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

2. Disaccharides (double sugars):

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

  • Lactose (milk sugar): glucose + galactose; naturally found in milk.

  • Maltose (malt sugar): forms when starch is broken down.

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

How does sugar affect the body?

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

2. Brain function:
The brain relies especially heavily on glucose. A short-term intake of sugar can improve concentration and reaction time, but too much sugar can have the opposite effects, such as energy crashes and restlessness.

3. Effects on insulin and energy balance:
Frequent blood sugar spikes caused by too much sugar lead to insulin fluctuations, which strain the metabolism and can trigger cravings. Over time, this can lead to insulin resistance, obesity, and metabolic disorders.

4. Mood and reward:
Sugar activates the brain’s reward system by stimulating the release of dopamine, similar to other pleasurable substances. This explains why sugar makes you feel “happy” in the short term, but can also be highly addictive.

Natural vs. added sugar

  • Natural sugar: is found in foods such as fruit, milk, or vegetables, where it is accompanied by fiber, water, vitamins, and minerals. This combination slows absorption and has a positive effect on health.

  • Added sugar: is incorporated into foods during industrial processing (e.g. table sugar, glucose syrup, fructose, maltodextrin) and provides energy but no nutrients.

Benefits (in moderate amounts)

  • Quick source of energy for the brain and muscles

  • Supports performance during intense physical activity

  • Can temporarily improve concentration and mood

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

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 breakdown of sugar in the mouth

  • Insulin resistance and type 2 diabetes

  • Fatty liver (non-alcoholic fatty liver disease)

  • Inflammatory processes and increased oxidative stress

  • Fluctuating energy and blood sugar levels

  • Increased risk of cardiovascular disease

Recommendations from nutrition associations

The World Health Organization (WHO) recommends that no more than 10% of daily energy intake should come from added sugar – ideally less than 5%.

That corresponds to about:

  • 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 – so it’s worth checking the ingredient list.

Conclusion

Sugar is a natural part of our diet and provides quick energy – completely harmless in moderate amounts. It becomes problematic when there is excessive consumption of added sugar, such as that found in soft drinks, sweets, and processed foods. Being mindful about sugar means preferring natural sources like fruit and reducing industrially added sugar. This helps keep blood sugar levels stable, energy evenly distributed, and health protected in the long term.

Sources

  1. World Health Organization (WHO). (2015): Guideline: Sugars 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.