Part I – how light diet becomes heavy
Recently, we have observed that people have become very interested in a ketogenic diet (i.e. a diet producing ketone compounds in the body). This is probably a result of a general increase in the popularity of low-carbohydrate diets. However, it should be remembered that the ketogenic diet differs quite significantly from diets low in carbohydrates.
It may last for a very specific time and is not recommended for all.
Biochemical differences between a traditional and a ketogenic diet
In order to understand the essence and effect of ketogenic diets, one should know the effect of ketone compounds on the human body.
Diets supplying a balanced quantity of carbohydrates and fats make the formed acetyl-CoA (coenzyme A acting in the metabolism as a carrier of groups coming from fatty acids) enter the Krebs cycle (the final metabolic cycle in aerobic organisms) during the burning of fats. The entry of acetyl-CoA into this cycle depends on the availability of one of the elements of the Krebs cycle, i.e. oxalacetate. By binding with oxalacetate, acetyl-CoA forms citrate, starting a new round of the cycle.
However, if the fat breakdown dominates with the deficiency of carbohydrates (what is possible in the case of improperly planned carbohydrate-low diets), the fate of acetyl-CoA is different. Oxalacetate is used for the glucose biosynthesis and is unavailable for the reaction with acetyl-CoA.
As a result, an excessive amount of acetyl-CoA is accumulated. It is condensed, what results in the formation of ketone compounds, i.e. acetoacetate, D-3-hydroxybutyrate, and acetone.
The breath of people in ketosis smells clearly of acetone. The main place where ketone compounds are formed is the liver. These substances travel to blood and are transported to tissues. Acetoacetate and 3-hydroxybutyrate are the main source of energy in the process of intracellular respiration.
Does the brain need ketone compounds?
In correct metabolism, the only fuel for the brain is glucose. The brain does not have energetic reserves and, therefore, it requires a constant supply of glucose, which freely gets in the brain tissue in its free form.
The consumption of glucose by the brain is app. 120 g daily. App. 60% of the whole glucose consumption in the human body takes place in the brain.
In the period of fasting (no glucose), ketone compounds are the fuel for the brain instead of glucose.
Fatty acids cannot be used as fuel molecules because they are related to albumins (main proteins in blood plasma); therefore, they cannot get through the blood-brain barrier.
However, ketone compounds can be transported to the brain. The replacement of glucose as a fuel with ketone compounds minimizes the breakdown of proteins during fasting.
The adaptation of the brain to use ketone compounds is gradual and possible with slow reduction of glucose supply. It has been determined that the brain can be nourished with ketone compounds in app. 70%.
Do muscles use ketone compounds?
The main fuels for muscles include glucose, fatty acids, and ketone compounds.
Unlike brain tissue, muscles contain much glycogen (3/4 of total glycogen in the human body). Glycogen (polysaccharide formed of app. 100,000 glucose molecule rests) easily releases glucose used in muscle tissue.
Muscles, like the brain, cannot release glucose to blood and other tissues.
In the actively working skeletal muscles, the rate of glycolysis significantly exceeds the rate of the citric acid cycle. In the conditions of anaerobic glycolysis (during the work of muscles), pyruvate is reduced to lactate, which is transformed into glucosis after getting into the liver. This way, a part of metabolic burden is passed from muscles to the liver.
In a resting muscle (aerobic conditions), the main fuel includes fatty acids.
Ketone compounds can be a fuel for the cardiac muscle. In fact, the cardiac muscle prefers to use ketone compounds to glucose. The similar situation can be observed in energetic processes in kidneys and lungs.
Is the presence of ketone compounds in blood good or bad?
In blood plasma, there is an almost constant level of ketone compounds.
If the level of ketone compounds increases slowly, tissues (apart from liver tissue) start to use more and more ketone compounds for energetic processes.
There are various reasons for the increased levels of ketone compounds in blood or urine. They include:
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- diabetic acidosis
- low-carbohydrate diet
- high-fat diet
- prolonged vomiting
- hepatic glycogenesis
- chronic fevers
- after taking STH
- Cushing syndrome
- prolonged insulin overdose
- ethanol and isopropyl alcohol poisoning
- treatment with 11-oxy steroids
- low-carbohydrate and high-fat diets
- severe anaemia
- chronic fevers
- prolonged vomiting
All these cases should be monitored by determining ketone compound levels in urine. A popular method to determine urine levels of ketone compounds is the use of test strips.
Ketone euphoria, i.e. how ketone compounds influence human body
Ketones have a specific influence on a human body.
What is surprising is the euphoric effect of ketone compounds, which occurs frequently at the beginning of a low-carbohydrate diet. This great physical and mental condition deteriorates after 2-3 months of a ketogenic diet.
Other frequent symptoms include the loss of appetite, changed smell of sweat, urine, and breath, increasing thirst, sleepiness, and constipations.
How long should the ketogenic diet be and who should use it?
A classic ketogenic diet may be used no longer than for 3-4 months. During this time, patients should take regular advice of a dietician or a physician. A physician will recommend changes in the diet or a continuation of the low-carbohydrate diet.
Ketogenic diets are best when there is a prevalence of catabolic processes over anabolic ones and in so-called quick oxidizers.
Excessive catabolism is related to the basic tissue environment and more acid blood.
Potassium levels are reduced and calcium levels increase in tissues. Increased urine pH, high ESR, low eosinophilia, and increased oxygen consumption can be observed. In cellular membranes, fatty acids prevail over sterols.