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FAQs: Understanding Ketosis

0 Comments | May 13, 2013

Understanding Ketosis

What are ketones?

Ketone bodies (ketones) are three water-soluble compounds that are produced as by-products when fatty acids are broken down for energy in the liver. Two of the three are used as a source of energy in the heart and brain while the third (acetone) is a waste product excreted from the body. In the brain, they are a vital source of energy during fasting. Although termed “bodies”, they are dissolved substances, not particles.

Ketone bodies can be used for energy. Ketone bodies are transported from the liver to other tissues, where acetoacetate and beta-hydroxybutyrate can be reconverted to acetyl-CoA to produce energy, via the citric acid cycle.

The heart preferentially utilizes fatty acids for energy under normal physiologic conditions. However, under ketotic conditions, the heart can effectively utilize ketone bodies for energy.

The brain gets a portion of its energy from ketone bodies when glucose is less available (e.g., during fasting, strenuous exercise, low carbohydrate, ketogenic diet and in neonates).

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How does our body use ketones?

In the event of low blood glucose, as it is the case in ketogenic diets, most other tissues have additional energy sources besides ketone bodies (such as fatty acids), but the brain has an obligatory requirement for some glucose.

After the diet has been changed to lower blood glucose for 3 days, the brain gets 25% of its energy from ketone bodies. After about 4 days, this goes up to 70% (during the initial stages the brain does not burn ketones, since they are an important substrate for lipid synthesis in the brain). Furthermore, ketones produced from omega-3 fatty acids may reduce cognitive deterioration in old age.

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Is ketosis dangerous?

No, it is not. Ketoacidosis, not ketosis, is the dangerous condition you may have heard or been told about – many confuse the two, even practitioners!

In normal individuals, there is a constant production of ketone bodies by the liver. The concentration of ketone bodies in blood is maintained around 1 mg/dl. Their excretion in urine is very low and undetectable by routine urine tests.

When the rate of synthesis of ketone bodies exceeds the rate of utilization, their concentration in blood increases; this is known as ketonemia. This is followed by ketonuria – excretion of ketone bodies in urine. The overall picture of ketonemia and ketonuria is commonly referred as ketosis. Smell of acetone in breath is a common feature in ketosis.

When a type 1 diabetic suffers a biological stress event (sepsis, heart attack, infection) or fails to administer enough insulin they may suffer the pathological condition ketoacidosis. Liver cells increase metabolism of fatty acids into ketones and glucose via glycogenolysis in an attempt to supply energy to peripheral cells which are unable to transport glucose in the absence of insulin. The resulting very high levels of blood glucose and ketone bodies lower the pH of the blood and trigger the kidneys to attempt to excrete the glucose and ketones. Osmotic diuresis of glucose will cause further removal of water and electrolytes from the blood resulting in potentially fatal dehydration, tachycardia and hypotension.

Individuals who follow a low-carbohydrate diet will also develop ketosis, sometimes called nutritional ketosis, but the level of ketone body concentrations are on the order of 0.5-5 mM whereas the pathological ketoacidosis is 15-25 mM.

As the mainstream diet is so high in carbohydrate that ketosis is rarely seen without starvation or ketoacidosis, many practitioners mistake well regulated nutritional ketosis for pathological ketoacidosis.

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What is ketoacidosis?

Ketoacidosis is a life-threatening condition that must be immediately addressed. Not to be confused with ketosis.

Two out of three types of ketone bodies are acidic, and, if levels of these ketone bodies are too high, the pH of the blood drops, resulting in ketoacidosis.

Ketoacidosis is known to occur in untreated type I diabetes (diabetic ketoacidosis): when a type 1 diabetic suffers a biological stress event (sepsis, heart attack, infection) or fails to administer enough insulin they may suffer the pathological condition ketoacidosis. Liver cells increase metabolism of fatty acids into ketones and glucose via glycogenolysis in an attempt to supply energy to peripheral cells which are unable to transport glucose in the absence of insulin. The resulting very high levels of blood glucose and ketone bodies lower the pH of the blood and trigger the kidneys to attempt to excrete the glucose and ketones. Osmotic diuresis of glucose will cause further removal of water and electrolytes from the blood resulting in potentially fatal dehydration, tachycardia and hypotension.

Ketoacidosis is also known to occur in alcoholics after prolonged binge-drinking without intake of sufficient carbohydrates (alcoholic ketoacidosis).

Less commonly, some patients with poorly controlled type 2 diabetes may have detectable levels of plasma ketones without significant acidosis.

Individuals who follow a low-carbohydrate diet, will develop ketosis, sometimes called nutritional ketosis, but the level of ketone body concentrations are on the order of 0.5-5 mM whereas the pathological ketoacidosis is 15-25 mM.

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What is ketogenesis?

Ketogenesis is the process by which ketone bodies are produced as a result of fatty acid breakdown.

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