Time read: 9 MintuesWhen we think about sugar, we usually think about weight, diabetes, or dental health. However, in recent years, evidence has been accumulating that brain health is also linked to our diet and how the body regulates blood sugar levels.
It is important to start with the essentials: the brain needs glucose to function. Therefore, sugar is not “brain poison,” and there is no reason to fear every fruit, carbohydrate, or occasional dessert.
The important question is not whether we ate something sweet, but how much added sugars we consume, how often, and what our long-term dietary pattern and lifestyle look like.
Not Every Source of Sugar Comes in the Same “Packaging”
A whole fruit and a sugary drink can both contain sugar, but they do not affect the body in the same way. Whole fruit also contains fiber, water, vitamins, and other plant components, which typically slow down eating and sugar absorption.
On the other hand, sugary drinks, sweets, and pastries can deliver a large amount of added sugar quickly, without a comparable amount of fiber and nutrients.
After eating carbohydrates, blood glucose levels rise, and the body secretes insulin, which helps transport glucose into the cells. For most healthy people, this is a natural process that the body knows how to regulate.
Therefore, it is incorrect to say that every cookie immediately causes a “sugar crash,” brain fog, or memory impairment.
The term “brain fog” is a colloquial description for feelings like difficulty concentrating, fatigue, or sluggish thinking, rather than a medical diagnosis. Such feelings can arise for many reasons, including lack of sleep, stress, dehydration, medications, or a heavy meal – and not necessarily because of sugar alone.
The primary scientific concern is the cumulative picture: A high and continuous consumption of added sugars, especially as part of an unbalanced diet, may be associated with poorer metabolic and cognitive health.
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What Do Studies Say About Sugar and Cognition?
A systematic review and meta-analysis published in the journal Nutrients examined 77 studies dealing with free and added sugars and cognitive function. The researchers found that high and continuous consumption of added sugars may be linked to poorer cognitive performance.
However, they also emphasized that results vary across different types of studies, and that further research is required to determine exactly which amounts and which sources of sugar affect which cognitive abilities.
In other words, the research does not say that an occasional dessert “erases memories.” It does point to the possibility that a consistent pattern of excess consumption may be one of many factors affecting the brain over the years.
Another study, published in 2023 that followed community-dwelling older adults, found that higher intake of sugar and calories derived from sugar was associated with a higher risk of developing dementia.
The links were particularly pronounced for high consumption of fructose and sucrose from sources such as sugary drinks, sweets, and processed desserts.
However, this was an observational study: it found a statistical correlation but does not prove that sugar alone causes dementia.
When the Body Struggles to Regulate Sugar, the Brain Can Also Be Affected
The more established link is between type 2 diabetes and cognitive decline. According to the 2026 American Diabetes Association guidelines, older adults with diabetes are at a higher risk for cognitive decline and various types of dementia compared to people without diabetes.
This connection likely does not stem from a single factor. Diabetes can present alongside hypertension, vascular damage, unbalanced lipid levels, inflammation, and other risk factors—all of which can also affect brain health.
Recent studies are also examining the significance of large fluctuations in glucose levels and prolonged periods where blood sugar is unregulated. A meta-analysis published in 2025 found that among people with type 2 diabetes, a longer duration of the disease, higher HbA1c levels, greater glucose variability, and episodes of low blood sugar were associated with a higher risk of dementia. Here, too, these are complex research correlations and not proof that every temporary change in glucose causes brain damage.
And What About Alzheimer’s?
Alzheimer’s disease is sometimes referred to as “type 3 diabetes” due to changes in insulin activity and glucose utilization found in the brains of people with the disease.
However, this is a research moniker and not an accepted medical diagnosis. Alzheimer’s is a complex, multifactorial disease. Diabetes and vascular health are part of the factors that may influence the risk, but they are not the sole explanation.
In fact, a 2024 expert commission report by The Lancet identified 14 risk factors for dementia that can, at least to some extent, be modified during life. Among these factors are diabetes, hypertension, high cholesterol, physical inactivity, smoking, and social isolation.
The report emphasizes that no single action guarantees prevention; rather, it is important to combine the management of medical risk factors with physical, social, and cognitive activity.
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So, What Can Be Done in Practice?
There is no need to stop eating sweets entirely. A more realistic approach is to focus on regular habits:
- Reduce, primarily, sugary drinks and foods high in added sugar. These allow for the rapid consumption of a large amount of sugar, often without a significant feeling of satiety.
- Prefer whole, fiber-rich foods. Vegetables, whole fruits, legumes, and whole grains provide energy alongside additional nutrients.
- Manage medical risk factors. For people with diabetes, hypertension, or high cholesterol, monitoring and treatment according to medical guidelines are also important for brain health.
- Incorporate movement and mental challenges into your routine. Brain health does not depend solely on diet. Physical activity, sleep, social connections, and cognitive activity are all part of the same broad picture.
And What About Cognitive Training?
Cognitive training does not replace a balanced diet, physical activity, or medical care. It can be integrated alongside them as one of the ways to maintain an active and mentally challenging routine.
The training sessions at Effectivate are designed to practice abilities such as memory, attention, and processing speed through gradual and accessible tasks.
The important combination is not between a “wonder food” and a “wonder game,” but rather between different habits that support the body and brain: a balanced diet, movement, good sleep, social connections, and regular cognitive practice.
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In Conclusion
Sugar is not an enemy of the brain, and an occasional dessert does not cause cognitive decline. What matters more is the cumulative pattern over time.
Recent studies point to a possible link between high and continuous consumption of added sugars and poorer cognitive function, and a more established link between diabetes and an increased risk of cognitive decline and dementia. However, brain health is influenced by many factors, not by a single food.
Therefore, the goal is not to achieve a perfect diet, but to build a balanced routine: fewer sugary drinks and processed foods, more whole food, movement, sleep, social interaction, and cognitive challenge.
Brain health is built from many small, repeated choices, in your meal, during a walk, and also in a few minutes of training with Effectivate.
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Sources
- Gillespie, K. M., White, M. J., Kemps, E., Moore, H., Dymond, A., & Bartlett, S. (2024). The Impact of Free and Added Sugars on Cognitive Function: A Systematic Review and Meta-Analysis. Nutrients, 16(1), 75.
- Agarwal, P., et al. (2023). Dietary Sugar Intake Associated with a Higher Risk of Dementia in Community-Dwelling Older Adults. Journal of Alzheimer’s Disease.
- Livingston, G., Huntley, J., Liu, K. Y., et al. (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
- American Diabetes Association Professional Practice Committee for Diabetes. (2026). Older Adults: Standards of Care in Diabetes—2026. Diabetes Care, 49(Supplement 1), S277–S296. https://doi.org/10.2337/dc26-S013
- Tabesh, M., et al. (2025). Associations of glycaemia-related risk factors with dementia in people with type 2 diabetes: A systematic review and meta-analysis.
