Studies Show That Low Carbohydrate Diets Prevent and May Even Reverse Dementia & Alzheimer’s Disease
It is estimated that the prevalence of dementia and Alzheimer’s Disease in the United States will increase 50% by 2035, and 110% by 2050. One in ten people over 65 years of age, and one in five over 80 years of age will be diagnosed with dementia in this century. Nearly 40% of people over the age of 90 years have some form of dementia. This risk rate approaches 25% for any given individual who lives into their late 80s.
Doctors have known for years that if you are a Type II diabetic, or even prediabetic, your risk of dementia increases dramatically. Nearly 80% of people with dementia are diabetic or prediabetic.
Alzheimer’s disease accounts for the vast majority of patients with dementia. However, the other major category of dementia is the dementia that results from damage to the small blood vessels of the brain, causing a lack of blood supply to certain areas of the brain. It makes sense that this “microvascular ischemic” dementia and high blood sugar levels would occur together. Elevations in blood sugar, and even the post-meal spikes in blood sugars seen in prediabetics, are known to damage blood vessels and can potentially contibute to the occurrence of a strokes
It is true that as the US population ages more people are at risk for dementia, but even independent of this fact the “age adjusted” rates dementia are increasing dramatically. As demonstrated in the graphs below, some medical researchers have suggested that that the dramatic increase in dementia in recent years may be at least partially caused by changes in the American diet 30 to 40 years earlier. In essence, they propose, the tremendous increase in carbohydrate intake since the 1970s may be related to the increase in dementia we are seeing in people 30 to 40 years later. In other words, as carbohydrate intake skyrocketed in the 1970s and 1980s (and has continued at very high levels since that time) this may have impacted brain health and function, and now increasing rates of dementia. Association does not prove causation. However, in consideration of the explosion in diabetes mentioned above, and the research studies reviewed below, high carbohydrate diets should be viewed as a possible contributing culprit to the increasing rates of dementia.
Average US Carbohydrate Intake Over Time By Year Projected Rates of Dementia In the United States
(Grams/Day) Over Time By Year (Millions of Cases/Year
A number of recent studies have demonstrated that low carbohydrate diets decrease the risk and degree of dementia in many patients. In some of these studies, a low carbohydrate diet has actually been associated with a reversal of the severity of cognitive decline in individual patients.
The first study, published in the Journal of Alzheimer’s Disease followed 940 people between the ages of 70 and 89 for four years. Patients were divided into groups based on their predominant diet type: high carbohydrate, high fat, or high protein. All patients at the onset of the study underwent a rigorous battery of cognitive tests to confirm they had no signs of cognitive impairment. (The original study group consisted of 1,289 patients, but 349 patients were rejected from participating in the study due to the possible presence of some mild preexisting cognitive impairment based on the initial testing.) All patients included in the study were followed for a period of 15 months. At the conclusion of the study 200 patients were found to have developed a form of dementia called mild cognitive impairment (MCI). MCI includes problems with memory, thinking, language and judgement. The study found that patients consuming high carbohydrate diets had four times the risk of developing MCI. Those whose diets were highest in fat (nuts, healthy oils) were 42% less likely to develop cognitive impairment, while those who had the highest intake of protein (chicken, meat, fish) had a reduced risk of 21%. The authors’ believed high glucose levels might affect the brain’s blood vessels and also play a role in the development of beta amyloid plaques. Those are proteins that are toxic to brain health and are found in the brains of people with Alzheimer’s. They also suggested that fats and proteins might be important to the brain in maintaining brain cell structure and the successful production of brain neurotransmitters (the chemicals that allow brain cells to communicate with each other).
In a separate 2019 study, also published in the Journal of Alzheimer’s Disease, John’s Hopkins researchers found that that a high-fat, low-carbohydrate diet may improve brain function and memory. The lead author of the study, Jason Brandt, Ph.D. provided a possible explanation for the study results. He explained that the brain uses sugar (glucose), which is a product of carbohydrate breakdown as its primary fuel source. However, in patients with early stage Alzheimer’s Disease the brain isn’t able to efficiently use glucose as an energy source. For these patients eating a high fat diet, produces an alternative source of energy that can be effectively utilized by the brain: ketones. For example, a in a person on a mildly ketogenic diet, consisting primarily of fat and protein (with limited amount of sugars and starches), the brain may use this alternative fuel source instead of glucose to circumvent the problem with brain glucose metabolism.
In a separate study done in 2018, researchers from the University of Kansas sought to determine whether low carbohydrate diets that switch on the body’s ketone production could be helpful in preventing and/or reversing Alzheimer’s Disease. The primary question they tried to answer was: “Do low carbohydrate diets have the potential to improve memory and cognition in people with Alzheimer’s Disease?” As part of the study design dietitians taught participants (with the aid of patient family members and/or caregivers) to eat a diet of 10% carbohydrate, 20% protein, and 70% fat without lowering the number of calories they were accustomed to eating. Cognitive tests were administered before the study began, periodically during the study, and at the conclusion of the study. Degree of ketosis was monitored with urine strips daily. (Ketones are become an energy source for the brain if large amounts of blood glucose are not available.) All participants who completed the study were determined to be in at least mild ketosis most study days (60.6% of study days, with an average blood ketone level estimated at .52 mmol/L). Results showed that cognitive tests improved significantly in 90% of study participants. On average scores improved 5 points on a standard 70-point scale test of memory, language, attention, and task completion. The authors noted that this improvement was better than any medication currently on the market for the treatment of Alzheimer’s Disease, including the most widely sold drug for this purpose, Aricept (donepezil). With Aricept, scores generally improve only 3 to 4 points.
There are handful of other scientific studies completed in the last decade which support the value of a low carbohydrate diet in both reducing the risk of dementia, and improving symptoms in patients already having cognitive impairment. There are likely several reasons for this. First, low carbohydrate diets delay and may even reverse cerebral “microvascular ischemia” or “hardening of the arteries” in the brain mentioned above. However, another contributing explanation, as suggested by the John’s Hopkins study, is that patients with dementia, especially patients with Alzheimer’s Disease, have more trouble utilizing blood glucose as a fuel source in comparison to people with healthy brains.
The human brain is an energy hog, demanding a constant supply of fuel to feed hungry, hard-working brain cells. People with Alzheimer’s Disease essentially have an energy crisis on their hands, so they are in desperate need of an alternative fuel source. Fortunately, ketones are a very good source of energy for the brain. It is speculated that ketones can step in as a good source of energy when the brains of patients with dementia cannot efficiently utilize blood glucose as a fuel source.
Since the early 1900s, low carbohydrate diets have been used to successfully treat people with brain disease. An example is seizures, in which low carbohydrate diets were the primary method of treatment of seizures until well into the 20th century. Even today, low carbohydrate diets that produce mild levels of ketosis are used to treat pediatric patients with seizures. It may just be that tapping into ketone metabolism may have powerful applications to other areas of brain health, including the prevention and treatment of dementia.
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