Brain on sugar: The sweet myth of the sugar rush

Author: Laure Pauly | Editor: Anja Leist

There is little scientific evidence of a “sugar rush” that causes hyperactivity or mood enhancement. In fact, the notion that sugar causes hyperactivity, especially in children, has been debunked.

Brain health is not just about avoiding disease, acing memory tests, or waiting until retirement to worry about it. It’s about how your brain helps you think, feel, connect, work, create, cope with stress, and enjoy life, every single day, from childhood to old age. And here’s the good news: there’s a lot we can do to protect and strengthen it along the way. Welcome to the surprisingly fun, deeply human, and very relevant world of brain health. 

Sugar – a primary source of energy for our brain

Glucose, a form of sugar, is a primary source of energy for every cell in our body. Our brain consumes around 20-25% of the body’s sugar-derived energy.  So, it’s reasonable to wonder: if we eat more sugar, do we have more energy and become more alert or feel better? Not quite.

Science busting the sweet myth

A meta-analysis¹ comparing the effect of sugar and artificial sweeteners, such as aspartame, found no significant effect of sugar on behaviour and cognition in children. Similarly, another review² did not find evidence that sugar consumption has a beneficial effect on any aspect of mood. 

Why do we still believe in the sugar rush?

One explanation might be the expectation effect, a placebo-like phenomenon where simply believing that sugar will energize us can make us feel more alert or happier³. Context also plays a role. At children’s parties, for example, the excitement, social interaction, and stimulation may be misattributed to sugar intake. Parents might observe hyperactivity and link it to sweets, when in reality, it’s the environment that’s driving the behavior.

Sugar – friend and enemy of the brain?

Even though our brain depends on sugar, and without it we would not be able to function properly, a high sugar intake over time can have serious consequences. In the long-term, it may contribute to metabolic disease like type 2 diabetes, which is increasingly recognized as a major risk factor for cognitive decline and dementia⁴.  Furthermore, in the short-term, increased sugar intake can also have consequences. While the sugar rush is a myth, the sugar crash is very real. After consuming a large amount of sugar, research shows that people experience increased fatigue within 30 minutes and reduced alertness within 60 minutes². 

How much sugar is too much?

To protect both physical and cognitive health, the World Health Organization (WHO) recommends limiting free sugar* intake to less than 10% of total daily energy intake⁵. For an average adult consuming around 2000 kcal per day, this should be not more than 200 kcal from free sugar per day. This translates to roughly 50 grams or 12 teaspoons of free sugar per day. For additional health benefits, WHO suggests reducing sugar intake even further to below 5% of daily energy, which equals 25 grams or roughly 6 teaspoons of sugar per day. That might still sound like a lot, until you realize that just one can of soda contains approx. 35 grams (or more) of sugar, already exceeding the lower recommended limit. Don’t worry, when sugar intake is significantly reduced or when fasting, the body can switch to producing ketones from fat as an alternative energy source. This metabolic switching between sugar- and fat-burning is by some experts considered important for brain health as well.

*Free sugar include monosaccharides and disaccharides added to foods by the manufacturer, cook or consumer, and sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates⁶.

All in all, we can say that sugar is essential for brain function, but the way we consume it matters. While the idea of a “sugar rush” is more myth than fact, the real effects of excessive sugar intake, like the sugar crash, and long-term risks, are well documented. Moderation is key: our brains need sugar, but too much can do more harm than good. Understanding the science behind sugar helps us make smarter choices for both our mental and physical well-being.

For better readability of the text, the assistance of Microsoft Copilot, an AI language model based on the GPT-4 architecture, secured with UL enterprise data protection, has been used.

1. Wolraich ML, Wilson DB, White JW. The Effect of Sugar on Behavior or Cognition in Children: A Meta-analysis. JAMA. 1995;274(20):1617–1621. doi:10.1001/jama.1995.03530200053037
2. Mantantzis, K., Schlaghecken, F., Sünram-Lea, S. I., & Maylor, E. A. (2019). Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood. Neuroscience & Biobehavioral Reviews, 101, 45–67. https://doi.org/10.1016/j.neubiorev.2019.03.016
3. Hoover, D.W., Milich, R. Effects of sugar ingestion expectancies on mother-child interactions. J Abnorm Child Psychol 22, 501–515 (1994). https://doi.org/10.1007/BF02168088
4. Livingston, G., Huntley, J., Liu, K. Y., Costafreda, S. G., Selbæk, G., Alladi, S., Ames, D., Banerjee, S., Burns, A., Brayne, C., Fox, N. C., Ferri, C. P., Gitlin, L. N., Howard, R., Kales, H. C., Kivimäki, M., Larson, E. B., Nakasujja, N., Rockwood, K., . . . Mukadam, N. (2024). Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet, 404(10452), 572–628. https://doi.org/10.1016/s0140-6736(24)01296-0
5. WHO Guideline: sugar intake for adults and children: https://www.who.int/publications/i/item/9789241549028 .
6. WHO Factsheet about Sugar : https://cdn.who.int/media/docs/librariesprovider2/euro-health-topics/obesity/sugars-factsheet.pdf