You probably already know what I’m about to tell you. If you have a sweet tooth you may not want to hear it, but here it goes: Sugar is bad for you. #NewsFlash Not a very revolutionary statement, but it’s true.

It’s common knowledge that consuming too much sugar can lead to obesity, diabetes, hyperactivity, etc. The list of health effects (both temporary and long-term) is long—as is the list of foods and drinks with added sugar we consume every day. But there is one evil of sugar you may not be aware of yet: sugar slows down your brain.

Research has found that all that sugary goodness not only hinders our ability to form new memories but also leads to an increased risk for long-term conditions such as dementia. Read on below to find out what kind of effect that extra cookie might have on your brain.

[See also: Optimize your brain health for effective studying]

So, does sugar help with studying?

No. In fact, it is just the opposite. Overeating, poor memory formation, poorer learning, depression, and dementia—each of these has been linked in recent research to the over-consumption of sugar. And these linkages point to a problem that is only beginning to be better understood: what our chronic intake of added sugar is doing to our brains.

According to the U.S. Department of Agriculture (USDA), the average American consumes 156 pounds of added sugar per year. That’s five grocery store shelves loaded with 30 or so one pound bags of sugar each. If you find that hard to believe, that’s probably because sugar is so ubiquitous in our diets that most of us have no idea how much we’re consuming. The Center for Disease Control (CDC) puts the amount at 27.5 teaspoons of sugar a day per capita, which translates to 440 calories—nearly one quarter of a typical 2000 calorie a day diet.

The key word in all of the stats is added. While a healthy diet would contain a significant amount of naturally occurring sugar (in fruits and grains, for example), the problem is that we’re chronically consuming much more added sugar in processed foods, generally in the rapidly absorbed form of fructose.

That’s an important clarification because our brains need sugar every day to function. Brain cells require two times the energy needed by all the other cells in the body; roughly 10% of our total daily energy requirements. This energy is derived from glucose (blood sugar), the gasoline of our brains. Sugar is not the brain’s enemy—added sugar is.

Research indicates that a diet high in added sugar reduces the production of a brain chemical known as brain-derived neurotrophic factor (BDNF). Without BDNF, our brains can’t form new memories and we can’t learn (or remember) much of anything. Levels of BDNF are particularly low in people with an impaired glucose metabolism—diabetics and pre-diabetics—and as the amount of BDNF decreases, sugar metabolism worsens.

In other words, chronically eating added sugar reduces BDNF, and then the lowered levels of the brain chemical begin contributing to insulin resistance. That eventually leads to type 2 diabetes and metabolic syndrome, which, in turn, eventually leads to a host of other health problems. Once you're at this point, your brain and body are in a destructive cycle that’s really hard to reverse from.

Sugar and mental health

You may be asking yourself "does sugar help with studying?" (which it doesn't), but you should also be wondering about how sugar impacts mental health overall. Research has also linked low BDNF levels to depression and dementia. It’s possible that low BDNF may turn out to be the smoking gun in these and other diseases, like Alzheimer’s, that tend to appear in clusters in epidemiological studies. More research is being conducted on this subject, but what seems clear in any case is that a reduced level of BDNF is bad news for our brains, and chronic sugar consumption is one of the worst inhibitory culprits.

Other studies have focused on sugar’s role in over-eating. We intuitively know that sugar and obesity are linked (since sugar is full of calories), but the exact reason why eating sugar-laden foods seems to make us want to eat more hasn’t been well understood until recently.

New research has shown that chronic consumption of added sugar dulls the brain’s mechanism for telling you to stop eating. It does so by reducing activity in the brain’s anorexigenic oxytocin system, which is responsible for throwing up the red “full” flag that prevents you from gorging. When oxytocin cells in the brain are blunted by over-consumption of sugar, the flag doesn’t work correctly and you start asking for seconds and thirds, and seeking out snacks at midnight.

Eat a diet low in added sugar for better health—and better exam results

What these and other studies strongly suggest is that most of us are seriously damaging ourselves with processed foods high in added sugar, and the damage begins with our brains. Seen in this light, chronic added-sugar consumption is no less a problem than smoking or alcoholism. And the hard truth is that we may have only begun to see the effects of what the endless sugar avalanche is doing to us.

Instead, focus on eating a balanced diet that's low in added sugars. This will not only help you avoid the severe health effects of added sugar, but also help you study better. With the improved focus and endurance from your healthy diet, you'll be better able to function at work and in school.

Need something to counteract the effects of sugar and contribute to a sharper brain? Check out Brainscape, the intelligent flashcard-based study system that can help you learn dozens of subjects and stay engaged without the need for stimulants!


Krabbe, K., Nielsen, A. R., Krogh-Madsen, R., Plomgaard, P., Rasmussen, P., Erikstrup, C., ... & Secher, N. H. (2007). Brain-derived neurotrophic factor (BDNF) and type 2 diabetes. Diabetologia, 50(2), 431-438.

Mitra, A., Gosnell, B. A., Schiöth, H. B., Grace, M. K., Klockars, A., Olszewski, P. K., & Levine, A. S. (2010). Chronic sugar intake dampens feeding-related activity of neurons synthesizing a satiety mediator, oxytocin. Peptides, 31(7), 1346-1352.

Molteni, R., Barnard, R. J., Ying, Z., Roberts, C. K., & Gómez-Pinilla, F. (2002). A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience, 112(4), 803-814.

Ruanpeng, D., Thongprayoon, C., Cheungpasitporn, W., & Harindhanavudhi, T. (2017). Sugar and artificially sweetened beverages linked to obesity: A systematic review and meta-analysis. QJM: An International Journal of Medicine, 110(8), 513-520.