Introduction The ketogenic diet has been used since the beginning of the 20th century to reduce the incidence of epileptic seizures, and over time its application to other diseases has been studied.
This diet is characterized by a high content of unsaturated fatty acids, few carbohydrates and a normal protein content. While in a traditional diet there is about 55% of the energy value in the form of carbohydrates, about 30% fat and 15% protein, these proportions in the classic ketogenic diet are 8% for carbohydrates, 90% for lipids and about 7% for proteins. The most common form of the ketogenic diet includes mostly long-chain fatty acids.
The drastic changes induced by the ketogenic diet in eating habits are difficult to maintain in a long-term perspective. This is because high volumes of high fat components in the diet (cheeses, eggs, butter, oils, meat, etc.) can lead to nausea, vomiting, constipation and loss of appetite.
Adverse effects of the ketogenic diet The ketogenic diet, as a high-fat, low-carb diet, is associated with some insufficiency in the energy value of food portions and leads to metabolic effects that ultimately reduce body weight. People suffering from neurodegenerative diseases are at high risk of malnutrition and therefore this type of diet seems a priori to be contraindicated for them. People with neurodegenerative diseases suffer from sarcopenia which is often fatal.
According to current recommendations, people at risk should consume 1.0 to 1.2 g of protein/kg per day, or even more if they are physically active. The ketogenic diet, particularly when the energy value of the diet decreases, may therefore lead to a protein intake that is too low, although its contribution to the energy value of the diet may be normal or even higher than recommended. Such a situation can lead to the catabolism of structural proteins (especially in the muscles).
In individuals with insulin resistance, diabetic acidosis can be identified, which is a disease state with ketone body concentrations above 25 mmol/L, resulting from insulin deficiency with a simultaneous increase in glucose concentration ( > 300 mg/dL) and a decrease in blood concentration. pH (pH < 7.3), which can cause death.
Ketogenic diet and Alzheimer's disease It is not easy to formulate a ketogenic diet, in fact saturated fatty acids are present everywhere in large quantities, particularly in foods associated with pleasure, desserts, dairy products, chocolates. Eating a single meal high in saturated fat is enough to reduce our ability to concentrate, much more than if it is a meal high in unsaturated fat. Epidemiological studies show that a diet rich in saturated fatty acids increases the risk of Alzheimer's disease.
Studies conducted on an animal model of Alzheimer's disease, however, indicate a possible beneficial effect of the ketogenic diet for this medical condition.
Reger et al. concluded that oral administration of medium-chain triglycerides elevates plasma levels of ketone bodies and may improve cognitive functioning in older adults with memory impairment.
Henderson et al. administered medium-chain triglycerides to subjects with mild and moderate Alzheimer's disease. Administration of this type of fat resulted in improved cognitive functioning. It should be noted, however, that no effect of this type was observed in subjects carrying the APOEε4 genotype.
Ota et al. administered medium-chain triglycerides to 20 patients with mild to moderate Alzheimer's disease. After 8 weeks, patients showed significant improvement in their immediate and delayed logical memory tests compared to their baseline score. At 12 weeks, they showed significant improvement in the Numerical Symbol Coding Test and Logical Immediate Memory tests compared to baseline.
In the Ketogenic Diet Retention and Feasibility Trial, 15 patients with Alzheimer's disease maintained a ketogenic diet supplemented with medium-chain triglycerides (approximately 70% of energy as fat, including triglycerides at medium chain; 20% of energy as protein; and less than 10% of energy as carbohydrate). They have observed that when fully achieved ketosis, the mean score of the cognitive subscale of the Alzheimer's Disease Rating Scale improved significantly during the diet but returned to baseline at its termination.
Krikorian et al. applied a high carbohydrate diet to 23 subjects with mild cognitive impairment. After 6 weeks of intervention, the authors observed an improvement in verbal memory performance in subjects on a low carbohydrate diet. The authors concluded that even short-term use of a low-carb diet could improve memory function in older adults at increased risk for Alzheimer's disease. Although the observed effect may be partly attributable to the correction of hyperinsulinemia, other mechanisms associated with ketosis, such as reduced inflammation and improved energy metabolism, may also have contributed to the improved neurocognitive functioning.
Adapted from "Role of Ketogenic Diets in Neurodegenerative Diseases (Alzheimer’s Disease and Parkinson’s Disease)" Dariusz Włodarek doi: 10.3390/nu11010169