Michael R. Eades, M.D.
Glucose is necessary for our survival, but it doesn’t have to come from our diet. Our bodies have all the metabolic machinery in place to produce all the glucose we need to function just fine without our having to eat a gram of the stuff. Now if we do eat some glucose in the form of sugar and/or starch, the body uses what it needs and stores the rest first as glycogen and then as fat. When we have little or no carbohydrate in our diet, the body reverses the process and breaks down the stored glycogen, which is released as glucose. When the glycogen is gone the body turns to protein as the raw material for glucose production. The conversion of protein to glucose takes place in the liver and is called gluconeogenesis, a word meaning literally the making from scratch, or genesis, of new glucose.
The liver requires energy to convert protein to glucose. Fat provides this energy. The liver burns fat to run the gluconeogenesis machine, but it doesn’t completely burn the fat to carbon dioxide and water, the typical products of the body’s fat combustion process. Instead the liver converts these incompletely burned fats into ketone bodies and releases them into the blood where they are made available for any tissues that might want or need them.
And boy do the tissues want them! The muscles, the heart, and, particularly, the brain greedily lap them up in preference to glucose and/or fat. These tissues lap them up for a reason. Ketones provide a lot of energy very efficiently. The heart, for example, operates about 28 percent more efficiently on ketones than it does on glucose. (I always think of this fact whenever I read Jane Brody and other diverse nutritional idiots rabbit on about ketones being poisons.)
Despite the brain’s and other tissues’ greedy hunger for ketones, they can only consume so much. At some point they get full and stop eating. The liver however doesn’t stop making the ketone bodies because the liver has to continue making the glucose that the body requires. As long as the liver is cranking out glucose, it is cranking out ketones. When the brain, muscles, heart etc. have had their fill, the ketones accumulate in the blood. The body ditches them as mentioned above through the urine and breath. There are other processes that take place to prevent the ketone levels from going too high that are too complex to deal with in this short post, but rest assured that as long as you aren’t a type one diabetic, your ketone levels will never get to a dangerous level.
Glucose is necessary for our survival, but it doesn’t have to come from our diet. Our bodies have all the metabolic machinery in place to produce all the glucose we need to function just fine without our having to eat a gram of the stuff. Now if we do eat some glucose in the form of sugar and/or starch, the body uses what it needs and stores the rest first as glycogen and then as fat. When we have little or no carbohydrate in our diet, the body reverses the process and breaks down the stored glycogen, which is released as glucose. When the glycogen is gone the body turns to protein as the raw material for glucose production. The conversion of protein to glucose takes place in the liver and is called gluconeogenesis, a word meaning literally the making from scratch, or genesis, of new glucose.
The liver requires energy to convert protein to glucose. Fat provides this energy. The liver burns fat to run the gluconeogenesis machine, but it doesn’t completely burn the fat to carbon dioxide and water, the typical products of the body’s fat combustion process. Instead the liver converts these incompletely burned fats into ketone bodies and releases them into the blood where they are made available for any tissues that might want or need them.
And boy do the tissues want them! The muscles, the heart, and, particularly, the brain greedily lap them up in preference to glucose and/or fat. These tissues lap them up for a reason. Ketones provide a lot of energy very efficiently. The heart, for example, operates about 28 percent more efficiently on ketones than it does on glucose. (I always think of this fact whenever I read Jane Brody and other diverse nutritional idiots rabbit on about ketones being poisons.)
Despite the brain’s and other tissues’ greedy hunger for ketones, they can only consume so much. At some point they get full and stop eating. The liver however doesn’t stop making the ketone bodies because the liver has to continue making the glucose that the body requires. As long as the liver is cranking out glucose, it is cranking out ketones. When the brain, muscles, heart etc. have had their fill, the ketones accumulate in the blood. The body ditches them as mentioned above through the urine and breath. There are other processes that take place to prevent the ketone levels from going too high that are too complex to deal with in this short post, but rest assured that as long as you aren’t a type one diabetic, your ketone levels will never get to a dangerous level.
Comments