Carbs, glucose and mental energy

A few months ago, I came across an interesting study on X.

The study included a series of case reports in which switching to a keto diet significantly reduced symptoms of OCD in three individuals across different age groups.

As someone who, during stressful periods, experiences occasional intrusive thoughts and compulsions - though not to the extent of clinical OCD - I naturally found these cases fascinating.

While reading through the article, it occurred to me that some of the proposed mechanisms behind OCD also relate to the concept of mental energy.

Such as impaired brain energy metabolism and an unbalance between excitatory and inhibitory neurotransmitters.

So, I decided to explore the connection between carbohydrate/glucose intake and its effects on OCD, mental energy, and cognitive performance.

Today’s insights are mainly drawn from four different scientific articles:

“Ketogenic Diet as a Nutritional Metabolic Intervention for Obsessive-Compulsive Disorder: A Narrative Review” Lounici et al, 2024

“Fuel for Thought? A Systematic Review of Neuroimaging Studies into Glucose Enhancement of Cognitive Performance” Peters et al, 2020

“Altered functional connectivity of the default mode network by glucose loading in young healthy participants” Ishibashi et al, 2018

“The Impact of Free and Added Sugars on Cognitive Function: A Systematic Review and Meta-Analysis” Gillespie et al, 2023

Today's newsletter

• OCD and the Keto diet:

• Takeaways:

• Glucose may acutely rise cognitive performance:

• Glucose intake at rest:

• Negative long-term effects of excess glucose intak …

OCD and the Keto diet:

The first study is a review investigated the ketogenic diet (KD) as a potential metabolic treatment for Obsessive–Compulsive Disorder (OCD). 

The authors describe how OCD is associated with metabolic dysfunctions such as insulin resistance, mitochondrial impairment, inflammation, oxidative stress and an imbalance of excitatory and inhibitory neurotransmitters in the brain.

All of these can negatively affect the brain’s efficiency and therefore plays an important role in mental energy.

With KD, an individual shifts the brain's primary energy source from glucose to ketone bodies.

This shift offers a more efficient and stable energy supply.

This may enhance mitochondrial function, reduce oxidative stress, stabilize neurotransmitter balance of GABA/glutamate (the brains inhibitory/excitatory neurotransmitters), and dampen chronic inflammation.

That a ketogenic diet can potentially lessen the symptoms of OCD, is absolutely fascinating.

And importantly for us, as many of the dysregulations associated with OCD, is also associated with mental energy problems, these results and the proposed underlaying mechanisms show signs that decreasing the intake of carbohydrates might have some interesting effects on mental energy.

So, lets have a closer look at the impact of carbohydrates on mental energy and performance.

From the following studies, some clear takeaways emerges.

Takeaways:

⚡ Glucose = short-term boost, long-term cost

Glucose intake can briefly enhance memory and attention, but regular high intake may result in the opposite.

🔥 Chronic sugar intake disrupts mental energy

Over time, excess sugar may impair brain efficiency by promoting oxidative stress, inflammation, and neurotransmitter imbalances, which potentially drains your mental energy.

Glucose may acutely rise cognitive performance:

Although excess carbohydrate intake might negatively impact mental energy, this systematic review by Peters, et al 2020, showed a positive effect of carbohydrate intake.

The study examined 11 studies using neuroimaging to explore how glucose ingestion affects brain function and cognition.

Most studies showed that after 8-12 hours of fasting, a single glucose drink alters brain activity, particularly in areas related to memory and attention, such as the hippocampus and frontal cortex.

However, only about half of the studies found corresponding improvements in cognitive performance.

The studies varied a lot in their design and quality, but overall glucose seemed to reliably influence neural activity in ways linked with enhanced memory and attention, although it didn’t always translate into improved performance. 

Glucose intake at rest:

In this study by Ishibashi, et al 2018, the authors investigated how increased blood glucose levels affect brain connectivity in young, healthy individuals.

They used resting-state fMRI and found that glucose loading (drinking a glucose solution) significantly reduced functional connectivity in the brain's default mode network (DMN) - specifically in the precuneus/posterior cingulate cortex (PC/PCC).

While reduced activity in the (DMN) can actually be beneficial during cognitively demanding tasks, reduced connectivity in the DMN during rest is not advantageous.

The DMN is primarily associated with self-focused thinking and internal reflection.

During tasks that require focus, we want this network to quiet down so we’re not distracted by intrusive thoughts like "What if I mess this up?" or "Do I have time to cook tonight?".

However, in this study, participants were observed during rest, which is a time where the DMN should be active and well-connected. 

Reduced connectivity in the DMN at rest may point to a brain that is less organized, less efficient, and potentially impaired in its ability to recover and reset cognitively. 

Negative long-term effects of excess glucose intake:

So, a picture emerges that carbohydrates in the form of glucose might be advantageous in the short term, if one is engaged in a cognitively demanding task. However, if glucose is ingested during rest, it may negatively alter brain connectivity.

But going back to the first study about OCD, we were mostly interested in finding out how carbohydrate intake – or the lack thereof – might impact mental energy and cognitive abilities in the long run.

A systematic review and meta-analysis by Gillespie, et al 2023, analyzed 77 human studies investigating the impact of free and added sugars on cognitive function.

The study included:

· 65 experimental trials (n = 3,831 participants),

· 9 cross-sectional studies (n = 11,456), and

· 3 cohort studies (n = 2,059).

The studies were conducted across various countries and covered different age groups (children, adolescents, young adults, middle-aged, older adults).

While one should always be cautious drawing any firm conclusions from such a diverse set of studies with diverse methodologies and participants, some interesting findings did emerge.

And they do seem to fit the picture form the other studies above.

The majority of the experimental studies focused on the short-term effects of glucose on memory, attention, and executive function.

These studies sometimes showed a temporary positive “glucose facilitation effect” on memory and executive functioning, just like what could be seen in the Peters et al, 2020 review.

However, most observational studies (cross-sectional and cohort) examined long-term sugar consumption, and showed a different picture.

These studies found strong associations between sugar consumption and impaired memory, global cognition, and executive function.

Overall, the review highlights that while acute sugar intake might briefly enhance certain cognitive tasks, chronic high intake of added sugars is likely to have a negative effect on cognitive health.

This aligns well with the findings from the OCD-focused review.

Excessive sugar intake is likely to cause blood sugar spikes, insulin resistance, inflammation, and oxidative stress - factors that disrupt brain connectivity and efficiency, as well as the balance between excitatory and inhibitory neurotransmitters.

Mental energy is, in many ways, dependent on two key factors: the availability of adequate energy supply to the neurons involved in a given task, and the maintenance of a healthy balance between excitatory and inhibitory neurochemicals.

Maintaining this energy supply requires a well-functioning systemic energy regulation, which is something that insulin resistance directly undermines.

Similarly, sustaining the balance of neurotransmitters is energetically demanding, making a stable energy environment essential.

Both inflammation and oxidative stress further impair these processes by interfering with metabolic efficiency and neuronal signaling.

Overall, these findings all points to the fact that there might be something positive to gain in terms of mental energy, with avoiding excess sugar/carbohydrate intake.

_{Disclaimer: The above is mainly based on the 4 articles mentioned in the beginning of this newsletter, and aims to provide key takeaways and a condensed overview of its content. While the essence is drawn from the original articles, some parts have been simplified or rephrased to enhance understanding. Please note that we at, OptiMindInsights or any other potential writers or contributors to our summaries, do not accept responsibility for any consequences arising from the use of these summaries and/or newsletters as a whole. The information provided should not be considered a substitute for personal research or professional advice. Readers are encouraged to consult the original articles for detailed insights and references. The summary does not include references, but they can typically be found within the original publication. Always exercise due diligence and consider your unique circumstances before applying any information in your personal or professional life. We refer to the creative commons for reproducibility rights.}