In 2020, more than 55 million people were living with dementia globally. By 2050, experts predict that number will rise to 139 million.
Alzheimer’s Disease is the most common form of dementia, accounting for 60–80% of cases.
As we age, it’s normal for brain cells, or neurons, to die.
However, in dementia, neurons are lost on a larger scale, and brain regions begin to shrink. This leads to a progressive decline in memory and thinking skills.
Although treatments can slow the progress of dementia or ease symptoms, none can halt its progression.
Scientists are testing a wide range of interventions, one of which is the keto diet — a high-fat, very low-carbohydrate diet.
Here, we’ll look at the evidence, but first, we’ll ask why scientists think the keto diet is worth exploring.
There are a number of theories, but we’ll focus on just three: glucose control, mitochondrial impairment, and inflammation.
The keto diet and glucose control
At ZOE, we know that the healthiest diet is a varied diet. So, we don’t recommend restrictive programs like keto. However, for some people, the keto diet is a lifeline.
For more than 100 years, scientists have used the keto diet to help treat people with epilepsy. And it can be incredibly effective for some.
More recently, scientists have also shown that the keto diet can help people with type 2 diabetes get better control over their blood sugar levels.
On the keto diet, carb intake is minimal. And when your body runs out of carbs as fuel, the liver burns fat for energy instead.
This process converts fats into ketones, which serve as a backup energy source.
And with less sugar in the body, there is less in the blood, helping keep blood sugar down. But what has this got to do with dementia?
If you’d like to learn why blood sugar levels are important even if you don’t have diabetes, read this article.
Sugar and the brain
Insulin resistance is a hallmark of prediabetes and type 2 diabetes.
When someone has insulin resistance, it means that their body does not respond to insulin effectively, and their cells have difficulty taking in sugar from the blood.
Individuals with Alzheimer’s also have insulin resistance — but in their brains. Scientists call this brain insulin resistance.
People with Alzheimer’s also have impaired glucose metabolism, which means the brain does not use glucose efficiently.
Some authors have called this “type 3 diabetes.”
Although the Alzheimer’s brain can’t use glucose effectively, it can still use ketones.
The theory goes that if the brain receives ketones as energy instead of glucose — as it does on a keto diet — it might help counteract problems with glucose control and restore some cognitive function.
Aside from brain glucose metabolism, the keto diet might also benefit people with dementia via another pathway.
Brain cells in people with Alzheimer’s have reduced numbers of mitochondria — the powerhouses of the cell. Because neurons are energy-hungry, this is a problem.
Experts believe that the loss of mitochondria plays a part in the brain cell death associated with Alzheimer’s.
Keto, however, might help boost the formation of new mitochondria, potentially reducing the rate of cell death in dementia.
A role for inflammation
As we age, levels of inflammation tend to increase, which experts call inflammaging.
Over recent years, scientists have shown that dementia is associated with inflammation. In contrast, there is evidence that the keto diet might reduce inflammation.
This provides another theoretical way the keto diet might help slow dementia: Keto’s anti-inflammatory effects might damp down the inflammation related to dementia.
Taking glucose control, mitochondrial impairment, and inflammation together, the theory that the keto diet might help treat dementia seems reasonable.
But is there any evidence to back it up?
What’s the evidence?
To date, few studies have investigated keto as a treatment for dementia. But encouraging results have emerged from some of these studies.
A study published in 2021 recruited 26 people with an Alzheimer's diagnosis.
The scientists compared a ketogenic diet with the participants’ regular diet as a control. They also gave the control group low-fat healthy-eating guidelines and optional recipes to use.
Each participant spent 12 weeks following one diet, 10 weeks eating as they usually would, and the last 12 weeks following the other diet.
So, all participants tried both diets, separated by a 10-week “washing out” period.
The scientists assessed participants before, during, and after each dietary intervention.
They measured their thinking skills, how they functioned day to day, and their quality of life.
Importantly, the researchers found that when people followed the keto diet, they reported improvements in daily function and quality of life compared with when they followed their usual diets.
The authors explain that the keto diet improved daily function more than standard medication normally does.
Similarly, they report that standard drugs have “inconsistent” effects on quality of life.
As the authors write, daily function and quality of life are “of great importance to people living with dementia.”
Join our mailing list
Sign up for fresh insights into our scientific discoveries and the latest nutrition updates. No spam, just science.
Thinking skills did improve on the keto diet, but this effect was not statistically significant. In other words, it might have been due to chance rather than the diet.
Only 21 of the 26 participants completed 12 weeks of the keto diet. However, half of those who completed the intervention said they planned to continue the diet.
Although the results are encouraging, there are limitations.
Importantly, there were only a small number of participants, and the keto intervention lasted only 12 weeks.
The scientists also mention that the keto diet resulted in weight loss, which may have impacted the results.
Scientists need to carry out more studies that replicate these findings before doctors can recommend the keto diet to patients.
A different approach
One of the major problems with using the keto diet as a treatment for dementia is adherence — it can be tough to stick to long-term.
Some researchers have side-stepped this issue by giving participants a drug that increases the levels of a particular ketone without needing to change their diets.
For instance, one study — including 152 participants with an Alzheimer’s diagnosis — generated intriguing results.
They concluded that, compared with a placebo, those who took a ketone-elevating drug scored better on cognitive tests.
Other studies have investigated whether this approach might work for people with mild cognitive impairment (MCI). MCI is memory loss and reduced thinking skills that sometimes lead to dementia.
Some of these studies have shown improvements in thinking skills, but others have not. The jury is out.
Can we conclude anything?
At this stage, we can’t say that the keto diet will help alleviate the symptoms of dementia. But we can say that it’s an idea worth pursuing.
If nothing else, this article underscores the complexity of dementia and helps us understand why it is so difficult to treat.
Although we only scratched the surface, we saw how glucose control, mitochondria, and inflammation all play a part in the debilitating symptoms of dementia.
And many other factors also play important roles.
Drugs can help slow dementia’s progression, but we are in dire need of more interventions.
Hopefully, as research continues, scientists will identify dietary interventions with real benefits for people with these conditions.
When you join ZOE, our at-home test will measure how your blood sugar and blood fat levels respond to food. We’ll also analyze your gut bacteria.
From this data, we can provide personalized nutritional advice to help you move toward your long-term health goals.
A placebo-controlled, parallel-group, randomized clinical trial of AC-1204 in mild-to-moderate Alzheimer's disease. Journal of Alzheimer’s Disease. (2020). https://pubmed.ncbi.nlm.nih.gov/32310169/
Antioxidant and anti-inflammatory activity of ketogenic diet: New perspectives for neuroprotection in Alzheimer’s disease. Antioxidants. (2018). https://www.mdpi.com/2076-3921/7/5/63
Benefits of use, and tolerance of, medium-chain triglyceride medical food in the management of Japanese patients with Alzheimer's disease: a prospective, open-label pilot study. (2016). Clinical Interventions in Aging. https://pubmed.ncbi.nlm.nih.gov/26811674/
Brain fuel metabolism, aging, and Alzheimer's disease. Nutrition. (2011). https://pubmed.ncbi.nlm.nih.gov/21035308/
Brain insulin resistance at the crossroads of metabolic and cognitive disorders in humans. Physiological Reviews. (2016). https://www.sciencedirect.com/science/article/abs/pii/S1474442220302313
Dementia statistics. (n.d.). https://www.alzint.org/about/dementia-facts-figures/dementia-statistics/
Efficacy of ketogenic diets on type 2 diabetes: A systematic review. Current Diabetes Reports (2021). https://link.springer.com/article/10.1007/s11892-021-01399-z
Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease – is this type 3 diabetes? Journal of Alzheimer’s Disease. (2005). https://content.iospress.com/articles/journal-of-alzheimers-disease/jad00400
Mechanisms of mitochondrial dysfunction in Alzheimer's disease. Molecular Neurobiology. (2016). https://pubmed.ncbi.nlm.nih.gov/26537901/
Medium-chain triglycerides improved cognition and lipid metabolomics in mild to moderate Alzheimer's disease patients with APOE4 -/-: A double-blind, randomized, placebo-controlled crossover trial. Clinical Nutrition. (2020). https://pubmed.ncbi.nlm.nih.gov/31694759/
Mitochondrial biogenesis in the anticonvulsant mechanism of the ketogenic diet. Annals of Neurology. (2006). https://pubmed.ncbi.nlm.nih.gov/16807920/
Mitochondrial dysfunction and cell death in neurodegenerative diseases through nitroxidative stress. Brain Research. (2016). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4821765/
On the central role of mitochondria dysfunction and oxidative stress in Alzheimer’s disease. Neurological Science. (2019). https://link.springer.com/article/10.1007/s10072-019-03863-x
Peripheral inflammatory markers in Alzheimer's disease: a systematic review and meta-analysis of 175 studies. Journal of Neurology, Neurosurgery, and Psychiatry. (2017). https://pubmed.ncbi.nlm.nih.gov/28794151/
Pilot feasibility and safety study examining the effect of medium chain triglyceride supplementation in subjects with mild cognitive impairment: A randomized controlled trial. BBA Clinical. (2015). https://pubmed.ncbi.nlm.nih.gov/26675661/
Randomized crossover trial of a modified ketogenic diet in Alzheimer’s disease. Alzheimer’s Research and Therapy. (2021). https://link.springer.com/article/10.1186/s13195-021-00783-x
Study of the ketogenic agent AC-1202 in mild to moderate Alzheimer's disease: a randomized, double-blind, placebo-controlled, multicenter trial. Nutrition and Metabolism. (2009). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2731764/
What is Alzheimer’s disease. (n.d.). https://www.alz.org/alzheimers-dementia/what-is-alzheimers