Struggling to focus? Your blood sugar may be why

A growing body of research suggests that blood sugar balance plays an important role in how well the brain functions day to day. While we often associate blood sugar with physical health, it also directly affects concentration, mood, energy levels and mental clarity.

Diets that support stable blood glucose, particularly those rich in whole fibre-containing foods and healthy fats, are increasingly linked to better cognitive performance, whereas frequent spikes from refined and ultra-processed foods may contribute to brain fog and reduced focus.

The link between blood sugar and brain function

The brain relies on a constant supply of glucose to function effectively, using around 20% of the body’s daily energy despite its relatively small size. However, this supply needs to be stable.

When blood sugar rises rapidly after eating, for example, after consuming refined carbohydrates or sugary foods, it is often followed by a sharp drop. These fluctuations can affect how the brain performs, leading to changes in attention, mood and energy.

Research shows that repeated glucose spikes and poor insulin sensitivity can impair how effectively brain cells use energy.

This may contribute to:

• reduced concentration and mental clarity
• increased fatigue and “brain fog”
• changes in mood, including irritability
• difficulty maintaining attention throughout the day

This has led to increasing interest in what is sometimes referred to as “Diabetes 3.0” – a casual term used to describe the connection between metabolic health and brain function, particularly when the brain struggles to use available glucose efficiently.

Why stable blood sugar can support cognitive health

Experts suggest that stable blood sugar may benefit the brain in several key ways:

• Sustained energy supply – providing a steady source of fuel for consistent mental performance throughout the day.
• Improved neurotransmitter function – supporting chemical messengers involved in mood, focus and motivation.
• Reduced inflammation – helping to protect brain cells from damage linked to metabolic stress.
• Better insulin signalling – allowing brain cells to respond effectively and use glucose efficiently.

Unlike sharp spikes and crashes, a more gradual release of glucose may help maintain focus and avoid the dips in energy that many people experience mid-morning and afternoon.

The role of dietary patterns

Rather than focusing on individual nutrients, overall dietary patterns appear to have the greatest impact on both metabolic and cognitive health.

Eating patterns that support stable blood sugar typically include:

• high intake of vegetables, fruits and legumes
• whole grains rather than refined carbohydrates
• healthy fats such as olive oil, nuts and seeds
• adequate protein from fish, plant sources or lean animal foods

These approaches share similarities with Mediterranean-style diets, which have been widely studied for their benefits to both metabolic and brain health.

Importantly, these benefits are not solely linked to weight or calorie intake. Improvements in blood sugar regulation and nutrient intake alone appear to support better cognitive function.

The impact of ultra-processed foods

Ultra-processed foods, including sugary drinks, packaged snacks, refined cereals and fast foods, can disrupt blood sugar balance due to their high levels of refined carbohydrates and low fibre content.

These foods are typically digested quickly, leading to rapid increases in blood glucose followed by crashes. Over time, this pattern may contribute to insulin resistance and reduced metabolic flexibility.

Regular consumption of ultra-processed foods has also been associated with poorer overall dietary quality, meaning lower intake of nutrients that support brain function:

• Fibre – slows glucose absorption and supports a healthy gut microbiome. Found in vegetables, legumes, whole grains, nuts and seeds
• Omega-3 fatty acids – support brain cell structure and function; found in oily fish, flaxseeds and walnuts.
• Magnesium – helps regulate blood sugar and supports the nervous system; found in leafy greens, legumes, nuts and whole grains
• B vitamins – important for energy production and neurotransmitter synthesis. Also found in the above foods.

Simple strategies to support blood sugar balance

The following strategies may help to support blood sugar balance:

• combining carbohydrates with protein, fats and fibre
• avoiding frequent high-sugar snacks and drinks
• incorporating light activity, such as walking after meals
• prioritising regular meals to reduce large fluctuations in blood sugar

Sleep and stress management are also important, as both can influence how the body regulates glucose and, in turn, how the brain functions.

A broader view of brain health

Cognitive health is influenced by multiple factors, including nutrition, movement, sleep and stress. Blood sugar regulation is just one important piece of this wider picture.

Rather than focusing on individual foods or quick fixes, supporting the brain is best approached through consistent daily habits that promote stable energy and overall metabolic health.

The shift in perspective moves the focus away from short-term fixes and towards daily habits that support brain health over the long term.

References

Baker, L. D., Espeland, M. A., Whitmer, R. A., et al. (2025). Structured vs self-guided multidomain lifestyle interventions for global cognitive function: The US POINTER randomized clinical trial. JAMA. Advance online publication. https://doi.org/10.1001/jama.2025.12923

Barnes, L. L., Dhana, K., Liu, X., et al. (2023). Trial of the MIND diet for prevention of cognitive decline in older persons. New England Journal of Medicine, 389(7), 602–611. https://doi.org/10.1056/NEJMoa2302368

Mason, A. C., Fatih, N., Sofat, R., Rentsch, C. T., Smeeth, L., Bhaskaran, K., Chaturvedi, N., & Garfield, V. (2025). Disentangling the relationship between glucose, insulin and brain health: A UK Biobank study. Diabetes, Obesity and Metabolism. Advance online publication. https://doi.org/10.1111/dom.70353