What are the cognitive benefits of a Keto Diet?

For those of you who have either heard of, or have experienced firsthand, the multiple benefits of a ketogenic diet, such as healthy weight loss and/or improved blood sugar control, you might not be aware of this eating style’s lesser known benefit, which is its potential positive impact on your brain’s health. Although purely anecdotal, many of those on Keto report improved overall brain function (i.e. less ‘brain fog’), less anxiety, improved mood, focus, and memory while in nutritional ketosis.

How Does the Keto Diet Protect Our Brain & Support Brain Function?

For one, ketone bodies, as a distinct and separate entity, have been shown to have singular properties which protect our nerve cells. One of their unique features is their ability to alter the metabolism of a cell’s mitochondria by increasing levels of ATP, thereby boosting its metabolic efficiency. Ketones actually provide a more efficient source of fuel (more energy per molecule) as compared to glucose. Ketone bodies have also been shown to decrease the production of free radicals in cells and tissues1This is important because high levels of free radicals can harm important cellular structures such as proteins and nucleic acids (i.e. DNA), and mounting evidence reveals that this form of oxidative stress plays a major role in the onset and/or progression of several chronic diseases. Another feature of the KD which could serve as a potential mechanism to protect the integrity of nerve cells is its impact on glucose levels and its inhibition of glycolysis2. This inhibition of glycolysis is known to exert strong anti-seizure effects, and is one of the fundamental mechanisms behind the effectiveness of the KD in treating epilepsy.

What are some cognitive benefits of the Keto Diet?

Although the ketogenic diet (KD) has long been recognized for its therapeutic role in treating nervous system disorders, namely epilepsy, there are strong indications that this diet may also be beneficial in the treatment of other degenerative neurological conditions, such as Alzheimer’s and Parkinson’s disease3. Additionally, over the past several years, there has been a number of research studies suggesting that the KD even has applications above and beyond its treatment for these disorders. Here are just a few of the documented cognitive benefits of the Keto Diet:

Memory Enhancement

A study by NIH’s National Institute on Aging was just completed in May of 2018, which aimed to examine the effect of the KD on memory loss and mild cognitive impairment (MCI). The intent of the study was to examine the effect of KD on cognitive impairment associated with Metabolic Syndrome. Insulin resistance, the hallmark of Metabolic Syndrome and Type 2 diabetes, can disrupt the way the body gets energy from food, and is a major risk factor for cognitive impairment and dementia. Researchers believe that a ketogenic diet, which promotes energy use from fats rather than carbohydrates, may reduce the symptoms associated with insulin resistance and improve brain function. This study hoped to demonstrate this benefit. The details of the study are listed here.

Although numerous studies have shown that a KD can slow and even reverse symptoms of memory loss and cognitive impairment in varying degrees of dementia, most of these studies have been performed on non-human mammals (i.e. mice). However, a recent study testing the effect of a KD on a group of older human adults with Mild Cognitive Impairment (MCI) over a six-week period revealed significant improvements in verbal memory as compared with the group on a high-carbohydrate diet (50% of total daily calories from carbs). Moreover, subjects on the KD also reaped additional significant health benefits in this relatively short period, including weight loss, a decreased waist circumference, and reductions in both their fasting blood glucose and insulin levels. The authors of the study concluded ‘These findings indicate that very low carbohydrate consumption, even in the short term, can improve memory function in older adults with increased risk for Alzheimer’s disease,” and ‘To our knowledge, these data demonstrate for the first time that carbohydrate restriction can produce memory enhancement in this at-risk population.”4

Improved Focus

For some of the same reasons the KD has shown to be beneficial in treating epilepsy, which is the alteration in the brain’s processing of glutamate, the KD has also been hypothesized to help our brain to focus. Chronic elevations of glutamate are linked to excessive excitability within the brain, and, during ketosis, less glutamate is metabolized and more of it becomes available for its conversion to glutamine, a precursor of the neurotransmitter Gamma-aminobutyric acid, or GABA5. GABA inhibits the stimulatory, or excitability, properties of glutamate and increased levels of GABA induce a calming effect on our brain. This counterbalance is fundamental to proper brain function and any disruption in this balance has the potential to lead to a number of neurological disorders.

Increased Mental Performance

A growing body of research is establishing a strong link between a dysfunctional or abnormal blood sugar metabolism and the wide spectrum of dementia, from mild cognitive impairment (MCI) to Alzheimer’s disease (AD). The most prevalent of these disorders in the US are insulin resistance (i.e. Metabolic Syndrome) and Type 2 diabetes (T2D).

Many health experts and researchers consider this link to be so compelling they have actually described Alzheimer’s as ‘Type 3 Diabetes’ or an ‘insulin-resistant brain state’, expanding on the argument that Alzheimer’s is a progressive metabolic disease of the brain.

This clear association between T2D and AD has fed into emerging research on the role of insulin in the regulation of memory and mental performance.

The exact mechanisms behind this association between insulin resistance and dementia are unclear but several have been proposed, including insulin resistance, hyperinsulinemia (excessive circulating levels of insulin), insulin deficiency, impaired insulin receptor and impaired insulin growth factor (IGF) signaling, and cell damage due to chronically elevated blood glucose levels6. The end result of these metabolic dysfunctions is a chronic energy deprivation of the brain’s cells, with each of these conditions leading to the brain’s decreased ability to use glucose as a source of fuel.

The KD, which provides an alternative energy source for our brain in the form of ketones, can prove to be beneficial in reversing this chronic energy deficiency to brain cells, and either staving off the symptoms associated with dementia or even helping to restore mental function and performance. In addition to the fact that the KD reduces baseline blood sugar levels, ketones do not require insulin to enter our brain cells. In fact, on a very low-carb diet, such as the KD, up to 70% of the brain can be fueled by ketones – the balance can be fueled by glucose which is produced in the liver. It is worth noting that individuals with features of insulin resistance, such as T2D, Metabolic Syndrome, and obesity, have a higher risk of developing AD, while individuals with AD often develop high blood sugar and insulin resistance7.

Deeper Sleep

Research on the KD has also revealed its beneficial impact on sleep quality. A summary of clinical studies that investigated the effect of dietary patterns on sleep demonstrated that the KD (at least over the short-term) increases the percentage of slow wave sleep (SWS) which is deep sleep (stage 4) and has a restorative function8. Impairments of sleep are a widespread feature of mental disorders. Individuals with anxiety disorders have been found to have significantly less deep sleep and overall sleep time. Although the mechanisms for this remain unclear, the strong association between sleep quality and its beneficial impact on our mental health is widely acknowledged. Anxiety and/or stress are further fueled by inadequate sleep and poor sleep quality. Many long-term adherents to the KD report they are able to sleep longer, sleep deeper, and feel more relaxed and rested when they wake up. Certainly, these claims are anecdotal, which further underscores the need for additional studies to confirm these numerous reports.

Mood Regulation

You can find numerous anecdotal reports on the internet claiming improved mood and an overall improvement in anxiety level on the KD. Although there are currently no known studies (at least that I’m aware of) examining the effects of KD on mood (including depression and anxiety) in humans, the KD might offer a viable strategy for those who seek an alternative to pharmacologic treatments for mood enhancing or regulating agents. Many of us have reservations about medications for anxiety, depression or mood enhancement for many reasons, which include their potential negative side effects, their efficacy, and even their affordability. It is essential that anyone considering the KD for their mental health do as much research as possible and educate themselves on the intricacies of this diet. If you’re already being treated for a mental health issue, you should definitely seek guidance, close supervision, and support from a medical professional prior to beginning an alternate treatment approach such as the KD, as this diet can have an impact on brain chemistry and directly interact with a wide variety of medications, especially psychiatric drugs. The following is an excellent article on the potential interactions of the KD and psychiatric medications.

Management of Autistic Behavior Symptoms

There is evidence that the ketogenic diet may be used in the management of autism spectrum disorder (ASD) as an additional or alternative therapy – this was demonstrated in a prospective pilot study carried out on children. Notably, the beneficial effects of the KD persisted during the diet-free intervals of the study, and, following  termination of the the KD, its beneficial effects were maintained for a relatively long duration9One of the hypotheses supporting the use of KD in individuals with autistic behavior is related to a deficiency of glucose oxidation in the brain, with ketone bodies offering both an alternative fuel source and the potential for improved mitochondrial function. The authors of a review of two independent studies on the beneficial effects of the KD in children with autism spectrum disorder symptoms, including the study mentioned above, concluded that the ‘ketogenic diet for autism spectrum disorder needs to be prescribed on a case-by-case basis, upon careful biochemical characterization and metabolic profiling’ (i.e. to rule out defects in fatty acid metabolism in children or monitoring potential risk factors for heart disease in older patients with ASD)10. This recommendation appears to be both an appropriate and valid one.

Key Takeaways

The ketogenic diet is gaining well-deserved recognition for its direct influence on brain function, potentially impacting mood, focus and mental performance, as well as age-related degenerative brain disorders. Just as the older population in the US continues to grow, the interest in how what we eat can affect our brain health is fast gaining traction. There appears to be legitimate motivation for considering the KD to help stave off the detrimental effects of an aging brain as well as to optimize its function regardless of age. Compared with glucose metabolism, ketone metabolism generates lower levels of oxidative stress, which has also been identified as a fundamental factor contributing to the degeneration of our brain and nervous system. The human brain also possesses significant potential for ketone metabolism, and on a more fundamental level, the KD theoretically has the potential to benefit any disease or condition for which its causality is linked to our cell’s ability to utilize energy.

  1. The effects of the ketogenic diet on behavior and cognition: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112040/
  2. Cerebral metabolic adaptation and ketone metabolism after brain injury: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2857668/
  3. The Ketogenic Diet as a Treatment Paradigm for Diverse Neurological Disorders: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3321471/
  4. Dietary ketosis enhances memory in mild cognitive impairment: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116949/
  5. Ketosis and Brain Handling of Glutamate, Glutamine and GABA: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722878/
  6. Insulin resistance as a key link for the increased risk of cognitive impairment in the metabolic syndrome: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4351418/
  7. Insulin resistance and Alzheimer’s disease: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4600067/
  8. Effects of Diet on Sleep Quality: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5015038/
  9. A modified ketogenic gluten-free diet with MCT improves behavior in children with autism spectrum disorder: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5863039/
  10. Potential Therapeutic Use of the Ketogenic Diet in Autism Spectrum Disorders: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074854/
Mary Paley

Fearless Dietitian; 30+ years as a professional dietitian; Master’s Degree in Nutrition and Dietetics at the MGH Institute of Health Professions; Lead research dietitian for several major pharmaceutical companies; Currently focused on health and wellness and the benefits of ketogenic diets for both obesity and diabetes management. MS, RDN, CDE, LD/N

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