In March – National Nutrition Month, there is a focus on health and diet, and the importance of nutrition for seniors. One controversial notion that I hear often is that of the benefits of the “ketogenic” diet for Alzheimer’s and other neuro-degenerative diseases. See for example: https://www.dietdoctor.com/low-carb/benefits/alzheimers
First let’s understand a couple of basic principles. The ketogenic diet involves low or zero carbohydrates, and high fat, high protein. Because the brain runs on glucose exclusively (unlike your muscles and other body tissues that can burn fat), the brain has no capacity to do this. One aspect of aging is the gradual (sometimes rapid) progress to reduced insulin sensitivity of the cells. While this is part of normal aging and should not result in any great decline in the capacity of the brain to use glucose, it is also related to the development of type 2 diabetes.
In this scenario – even if there is adequate glucose available, the reduced insulin sensitivity means it cannot be effectively transported into the cells. In diabetes, this then leads to increased blood glucose levels – the glucose starts to accumulate in the bloodstream rather than being used as fuel. This then leads to damage to blood vessels and other tissues and the complications of diabetes, of which decreased brain function is just one.
But when the body has no glucose fuel – either because none is consumed in the diet, or through fasting or starvation, it runs on fat. The liver makes a type of fuel that the brain can use when there is no glucose – ketones, sometimes called ketone bodies, referring to simple Carbohydrates which many would know – acetone, acetoacetate, R-Beta Hydroxybutyrate.
So, for the aging/diabetic brain – ketones provide an alternative fuel to restore the brain to normal metabolism. For other not well understood reasons, this fuel also appears to result in the slow down or cessation of senescence – the gradual deterioration in the cell function.
But these effects have been well known throughout the past century. For example, there is much research to show that children with epilepsy had reduced rate of seizures on a ketogenic diet and more recent research shows symptomatic improvement in Parkinson’s and Alzheimer’s and other dementia.
So why isn’t this being implemented whole sale? The simple answer is that the keto diet (and other fad diets – like Paleo) are not necessarily healthy. For a start, a lot of the research with children with epilepsy also provided an ideal opportunity to see long term effects of the keto diets, and this shows:
So why is the keto diet so popular and promoted? Firstly, it is likely that most people who go onto these types of diets are not strictly adherent – this is common with all diets. So, most people would be spared the worst impacts. But some of the claimed benefits are less than substantiated, for example weight loss – most of which is water. Another purported benefits – reducing blood glucose and therefore improving diabetes do not stand up to scrutiny. High levels of fatty acid metabolism resulting from keto diets INCREASE insulin resistance, therefore making diabetogenic tendencies worse in the long term. And remember insulin resistance is associated with impaired brain function – so it likely doesn’t do any good after all!
But then maybe we are asking the wrong questions – another trigger for ketogenesis is fasting, or caloric restriction. We already have plenty of evidence that caloric restriction improves longevity and reduces risk of chronic disease. It also appears that it induces similar positive effects on aging brains. Low glucose means the body naturally switches to ketone metabolism in the brain – which has the same effect as operating on a keto diet but without the risks.
This can be done without starvation – for example the 5:2 method or intermittent fasting. In other words, a conventional healthy diet – Vegan / Mediterranean / Asian – based on variety and whole foods: grains, leaf and root vegetables, legumes, fruits, lean meat, fish and other protein sources combined with mild caloric restriction could maintain or restore health, plus improve brain function, while not introducing the health risks of an extreme or extended version of the ketogenic diet.
For another expert perspective, and great interview with Dr Ed Blonz, a nutritionist and professor at UCSF – see this link: https://www.beingpatient.com/an-expert-explains-the-problems-with-a-keto-diet-for-alzheimers-prevention/
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Feasibility and efficacy data from a ketogenic diet intervention in Alzheimer’s disease: Alzheimer’s & Dementia: Translational Research & Clinical Interventions 4 (2018) 28-36
Systematic Review of the Use of Ketones in the Management of Acute and Chronic Neurological Disorders: JOURNAL OF NEUROLOGY AND NEUROSCIENCE ISSN 2171-6625 2017 Vol.8 No.2:188
Aging and Caloric Restriction Research: A Biological Perspective With Translational Potential: EBioMedicine 21 (2017) 37–44 http://dx.doi.org/10.1016/j.ebiom.2017.06.015
Caloric restriction increases ketone bodies metabolism and preserves blood flow in aging brain: Neurobiology of Aging 36 (2015) 2296e2303