Keto and Alzheimer’s: How Ketones Impact Brain Health and Function

The ketogenic diet is a very low-carb regimen that may positively impact Alzheimer’s dementia and type 3 diabetes, which is an emerging alternate name for Alzheimer’s because of the new diabetes symptoms that often come with it.

Approximately 5.8 million Americans live with Alzheimer’s dementia, and that number will continue to grow due to an aging population. (1) Currently, the standard of care treatment for Alzheimer’s aims to target symptoms and behavioral issues. There is currently no cure.

However, recent research on ketones and the keto diet suggests that going keto might have beneficial effects on Alzheimer’s disease.

Although the science of keto and Alzheimer’s is relatively recent, there’s already plenty to consider. Keep reading to learn more about the ins and outs of Alzheimer’s, how the ketogenic diet may slow or reverse it, and an evidence-based analysis of the risks and benefits of going keto.

Check out this Perfect Keto Starter Kit so you can begin your keto journey perfectly!

Understanding Alzheimer’s

Alzheimer’s disease, first reported by German psychiatrist Alois Alzheimer in 1907, is a neurodegenerative disease that leads to significant dementia symptoms. (2) It costs Americans around $350 billion per year and is a heavy burden for caregivers.

Recently, some have started to call it type 3 diabetes, referencing a phenomenon where Alzheimer’s patients experience diabetes with no other known cause.

Researchers estimate that over 25 million people have Alzheimer’s dementia. (3) It is the majority cause of dementia cases worldwide. Women experience Alzheimer’s at a higher rate than men and are more likely to get it earlier in life. (4)

Doctors divide the disease into early, middle, and late stages. Early Alzheimer’s is challenging to detect and may resemble normal age-related memory problems in older adults. The cognitive decline starts gradually, getting worse over time. Most patients don’t get a diagnosis until memory loss disrupts their quality of life. (5)

Symptoms of Alzheimer’s include:

• Episodes of forgetfulness
• Forgetting names of acquaintances
• Not recognizing close friends and family (in later stages)
• Confusion in unfamiliar situations
• Difficulty recalling recently-learned information
• Repeating conversations
• Deepening confusion over time
• Disrupted sleep
• Inability to understand one’s location
• Problems speaking
• Emotional and “acting out” symptoms such as depression, anxiety, aggression, verbal abuse, or paranoia
• Loss of independence, in later stages — may need a caretaker to help with eating and going to the bathroom

From the time of diagnosis, life expectancy is three to nine years. (6) Typically, complications of Alzheimer’s disease — such as dehydration, muscle wasting, or infections — result in death.

Root Causes

The causes of Alzheimer’s are complicated, and not all researchers agree about them. In fact, it’s a bit misleading to speak of a “cause” of Alzheimer’s in the first place.

Here’s a more scientific way to consider why and how the disease manifests:

• Risk factors: Traits that increase an individual’s risk of Alzheimer’s disease.
• Etiology: A triggering event or process that initiates the disease.
• Pathophysiology or pathogenesis: The disease process itself or the precise ways in which the disease affects the individual.

Research in all of these areas is critical for understanding, preventing, and treating Alzheimer’s. For example:

• Becoming familiar with risk factors can help you understand your risk. This is useful for risk reduction, early detection, and making important decisions ahead of time.
• Studying the etiology of Alzheimer’s, which happens to be the least understood aspect, relatively speaking, could lead to more effective prevention strategies.
• Understanding the pathophysiology of Alzheimer’s increases the hope for improved treatments that slow or reverse the course of the disease.

Risk Factors

According to the best scientific evidence we have, below are the key risk factors for Alzheimer’s disease:

• Age (7)
• Carrying one or two copies of the APOE4 gene (8)
• Familial history (9)
• Traumatic brain injuries (TBIs), also called concussions (10)
• Insulin resistance (11)
• High blood pressure (12)
• Chronic inflammation (13)
• Being overweight or obese (14)
• Smoking (15)

The single most predictive genetic marker for Alzheimer’s disease is having at least one copy of the APOE4 gene mutation, which can raise your risk two- to three-fold. On the other hand, the APOE2 gene mutation may be neuroprotective against Alzheimer’s. (16)

Recent Theories

Family history and risk genes don’t explain 100% of Alzheimer’s cases. Let’s get into the newest and most popular theories:

• Beta-amyloid plaque: At one time, the leading theory of Alzheimer’s disease was the beta-amyloid plaque theory. During autopsies, researchers would notice messy “tangles” caused by a type of plaque called beta-amyloid in the brains of deceased patients. (17) Drug companies developed drugs to reduce the formation of beta-amyloid plaque, but these medications have failed to deliver results in clinical trials. (18) While beta-amyloid formation definitely occurs in Alzheimer’s, it’s more likely a defense mechanism of the body than the primary cause.

• Vascular hypothesis: This theory is based on findings that Alzheimer’s patients have reduced blood flow to their brains. (19)
• Glucose hypometabolism: Observations from MRIs and PET scans show that less sugar reaches the brain cells of Alzheimer’s patients and that cells have difficulty using it as an energy source. (20)
• Mitochondrial dysfunction: This recent theory suggests that damaged mitochondria (the powerhouse of the cell) aren’t delivering energy to brain cells in Alzheimer’s. (21)
• Radical oxidative species (ROS) damage hypothesis: Some researchers theorize that poor-functioning cells impact the brain adversely by producing damaging free radicals. (22)

The odds are pretty high that several of these theories are correct. In fact, they may all be right. Unlike the beta-amyloid plaque theory, the other newer theories correlate with known risk factors for Alzheimer’s:

• Traumatic brain injuries and concussions impair blood flow to the brain and create free radicals. (23)
• Obesity, high blood pressure, and smoking damage the delicate lining of blood vessels. (24, 25)
• Insulin resistance, inflammation, and obesity result in mitochondrial dysfunction and excessive free radical production. (26)

Here’s where things get really interesting. The ketogenic diet can directly address blood flow, glucose metabolism, mitochondrial dysfunction, and related risk factors like hypertension, inflammation, and obesity.

The Ketogenic Diet and Alzheimer’s

There is currently no research definitively proving that keto can prevent or reverse Alzheimer’s. But there’s lots of evidence that keto is good for your brain.

Plenty of promising findings are encouraging researchers to continue studying keto’s relationship with Alzheimer’s. Below, you’ll learn how keto might reduce your risk of Alzheimer’s by improving modifiable risk factors.

For even better results, pair keto with regular exercise.

Ketosis and Brain Health

Going on a successful ketogenic low-carbohydrate diet should put you in ketosis, which refers to the natural production of ketone bodies by your liver. Ketone bodies, or ketones for short, are energy-rich molecules that your body produces in the absence of carbohydrates.

When you’re producing ketones, it means your body is running on fat for fuel instead of relying on carbs and sugar. To achieve and maintain ketosis, you must eat no more than 30-50 grams of carbs per day.

Both ketones and a lack of carbohydrates can have distinct positive effects on your brain function.

Here’s what you need to know about ketones and the brain:

• Ketones are the most efficient fuel for your brain’s neurons and are absorbed more readily than glucose (simple sugar). (27)
• Ketones have anti-inflammatory and antioxidant effects in the brain, meaning they can prevent or limit damage to cells. (28)
• Ketones in your brain result in epigenetic changes, including DNA methylation and gene expression. (29, 30)

Here’s what happens to your brain when you dramatically reduce carb intake:

• There’s less free radical production from glucose, meaning less cellular damage. (31)
• Your body, including your brain, becomes more sensitive to the effects of the hormone insulin. (32, 33)
• Similar to a fasting state, autophagy and mitophagy take place — meaning your brain can eliminate or “recycle” damaged tissue, cells, and mitochondria. (34)

Modifiable Risk Factors

Up to a third of all Alzheimer’s cases may be preventable by targeting the risk factors that can be changed — as opposed to aging, genes, or familial history, which are not modifiable. (35)

Now it’s time to take a look at how keto interacts with each of these modifiable risk factors of Alzheimer’s:

• Traumatic brain injury: There’s substantial evidence that keto reduces the adverse effects of TBIs in animals and may do the same in humans. (36) TBIs increase your risk of Alzheimer’s, but keto appears to reduce damage from TBIs.
• Insulin resistance: Some researchers have begun calling Alzheimer’s “type 3 diabetes” because severe insulin resistance increases the risk of the disease by up to four-fold. (37, 38) Both diabetes and Alzheimer’s involve glucose hypometabolism, mitochondrial dysfunction, and free radical damage. Insulin resistance increases Alzheimer’s risk, but keto can increase insulin sensitivity.
• High blood pressure: According to a systematic review from The British Journal of Nutrition, keto may have a unique ability to lower blood pressure that is not found with other diets. (39) That’s excellent news when it comes to lowering your risk of Alzheimer’s.
• Chronic inflammation: Chronic inflammation in your body can increase your risk of Alzheimer’s disease. High blood sugar, for example, is a known cause of chronic inflammation and also correlates to Alzheimer’s risk. (40) Keto enhances your mitochondrial health, reduces sugar intake, reduces oxidative stress, and reduces chronic inflammation.
• Overweight or obesity: Keto is fantastic for weight loss, which is great for decreasing your risk of Alzheimer’s. Unlike other diets, though, the ketogenic diet allows you to lose weight with minimal hunger and plenty of energy. (41) Instead of counting calories, study up on keto macros, make a keto grocery list, and follow through consistently. It’s also a good idea to measure your ketone levels when you start to make sure you’re actually in ketosis.
• Smoking: If you smoke, quitting may lower your risk of Alzheimer’s disease by up to 58%. (42) Believe it or not, a 2010 study published in the journal Trials concluded going keto may even make it easier to quit smoking for overweight adults. (43) Win-win!

Ketosis and Alzheimer’s Pathogenesis

Below are the four key pathways that appear to contribute to Alzheimer’s pathogenesis, as well as how the ketogenic diet may fight these pathways to Alzheimer’s:

• Vascular dysfunction and blood-brain-barrier issues: According to recent research, going keto may increase cerebral blood flow and help repair the vascular damage that occurs in Alzheimer’s patients. (44, 45)
• Glucose hypometabolism (insufficient glucose): Evidence demonstrates that the keto diet compensates for glucose hypometabolism by supplying ketones as an alternative fuel source.
• Mitochondrial dysfunction, which reduces energy production in the brain: A 2023 study concludes that ketone bodies and a ketogenic diet can improve mitochondrial function in the brain. (46)
• Free radical damage, which causes inflammation and cell damage: Ketones and ketosis work to “enhance mitochondrial function,” delivering more energy to the brain. (47) As a result, they also decrease inflammation and damage from free radicals.

In summary, the keto diet appears to address the four known pathways that contribute to the progression of Alzheimer’s.

However, the degree to which it can halt or even reverse the disease remains to be discovered.

Can Keto Reverse Alzheimer’s?

Short answer: No one knows yet if keto can reverse Alzheimer’s. There are no randomized controlled trials of the keto diet in Alzheimer’s patients, meaning there simply isn’t enough data to say one way or the other.

However, some healthcare providers do currently use the ketogenic diet to treat Alzheimer’s. (48)

There’s also promising evidence demonstrating improved cognition from studies of mild cognitive impairment (MCI) patients given ketogenic supplements like MCT oil and exogenous ketone bodies. (49, 50)

According to the authors of a 2019 study from the high-impact journal Nutrition: “[T]he ketogenic diet could be an effective treatment and prevention for Alzheimer’s disease, but both ketone production and carbohydrate restriction may be needed to achieve this.” (51)

Is Keto Safe?

The keto diet is controversial but safe in most cases. For every new promising finding, there are doctors, Hollywood celebrities, and internet “experts” who warn that you shouldn’t hop on the keto bandwagon.

Bottom line: Do not eat zero carbohydrates, and, if you have diabetes, only do the keto diet after consulting with your doctor. Those are the two primary situations in which dangerous side effects have been recorded — eating absolutely no carbs and going very low-carb with type 1 or type 2 diabetes.

Side note: if you’re breastfeeding, talk to your doctor before starting keto, and learn more about keto and breastfeeding here.

Below, I go into detail on myths and truths about the dangers of keto: ketosis vs. ketoacidosis, heart health, and nutritional deficiencies.

Ketosis vs. Ketoacidosis

To begin with, ketosis and ketoacidosis are not the same thing. Doctors who don’t specialize in diet and nutrition may confuse the two.

In nutritional ketosis, your blood ketone levels are between 0.6-3.0 millimoles per liter (mmol/L), while ketoacidosis occurs when your ketone levels become dangerously high — usually over 10 mmol/L. Ketones are acidic, so having very high ketone levels leads to problems.

Ketoacidosis primarily occurs in people with poorly managed diabetes, not as a result of the keto diet. It can also happen because of alcoholism, drug abuse, hyperthyroidism, heart attacks, or starvation.

While some reports of ketoacidosis associated with a low-carb diet do exist, they are incredibly rare. None have been reported in trials of properly-administered ketogenic diets without diabetes, alcoholism, or lactation. (52)

The authors of a 2018 peer-reviewed article on keto and Alzheimer’s summed it up perfectly: “The pathological ketoacidosis due to a lack of insulin in type 1 diabetes is not possible as [a] result of dietary changes alone.” (53)

Concerning Heart Health

Until recently, most doctors and scientists believed that high-fat diets and high-cholesterol diets resulted in “clogged arteries.” While this “low-fat” theory is now heavily contested, it’s fair to say that keto scares people who still buy into healthy fatty acids causing heart problems.

Robust evidence shows going keto actually improves many cardiovascular risk factors, including lowering “bad” cholesterol levels and raising “good” cholesterol levels. (54, 55)

Additionally, some evidence also shows higher total cholesterol may help prevent Alzheimer’s. (56)

Nutritional and Fiber Deficiency Worries 

Senior citizens and Alzheimer’s patients are at an increased risk for malnutrition. Some people worry that putting them on a restrictive diet could lead to nutrient deficiencies. Keto eliminates whole grains and other high-carb sources of fiber, leading to concerns that dieters won’t get enough.

There’s no excuse to skimp on fiber on the keto diet. You just have to get it from non-grain, whole-food sources instead of unhealthy processed foods.

A 2019 paper published in Current Developments in Nutrition found that Alzheimer’s patients can follow a nutritionally dense keto diet with medium-chain triglycerides (MCT oil), avocados, and non-starchy vegetables.(57)

As you investigate keto for yourself or a loved one, remember: it’s essential to ensure you include plenty of nutrient-dense foods and keto-friendly whole food sources of fiber. As long as you do, there’s absolutely no need to fret over fiber.

Try our free Keto Calculator to determine the exact amount of carbs, fat, and protein you need to reach and maintain your goal weight while on keto.

The Takeaway

Early research into the keto diet for Alzheimer’s is encouraging. Keto helps address risk factors for Alzheimer’s. Preliminary evidence also suggests it interacts favorably with the mechanisms that underlie the progression of Alzheimer’s.

Keto is safe for the vast majority of people, works phenomenally for various health issues, and is a great way to have more energy, clearer thinking, and fewer cravings. Stock up on nutrient-dense foods and get started on your healing journey.

Regardless of where you begin, always discuss your decision with a trusted doctor before starting a new diet. Be sure to set goals for improvement and monitor your results.

57 References