Ketosis:
Mystery
or Misconception?
by Tanya
Zilberter, PhD
Did you know that two ketone bodies, acetoacetate and
D-3-hydroxybutyrate,
are the only freely soluble fats (lipids) the body can use? This very
important fact explains a significant part of the ketosis mystery.
Ketosis: Mystery or Misconception?
Did you know that the two ketone bodies, acetoacetate
and D-3-hydroxybutyrate, are the only freely soluble fats (lipids)
the body can use? This very important fact explains a significant part
of the ketosis mystery.
Ketosis is achieved by reducing
carbohydrates to such a low level
that the body is forced to use incompletely metabolised fats (ketone
bodies)
as fuel.
Ketone bodies function as:
- Brain fuel.
The major role of ketone bodies is to
supply an alternative (to glucose) fuel for the brain in situations
where there are little or no carbohydrates available with food.
- Building blocks
for brain tissue. Ketone bodies are
precursors for the essential substance (acetyl-CoA) required in the
synthesis of lipid (myelin) in the neural cells.
The mechanisms for both major functions are
described in the tiniest details. It is well known how they act on the
cellular and intracellular (mitochondrial) levels and how they can
correct certain pathological states of the brain cells.
The concentration of ketone bodies in the
blood at any time represents
a balance between the rate of their production by the liver and the
rate
of their use by tissues.
What concentration is normal?
- Norm
(normoketonaemia) is a concentration of
total ketone bodies in blood
below 0.2 mmol/l.
- Ketosis
(hyperketonaemia) is concentrations
above this level but below the
ketoacidosis.
- Ketoacidosis
are concentrations above 7 mmol/l.
Past Technical Mistake Leads to Modern
Misconception
Historically, ketosis was associated with
the pathology of diabetes, resulting
in the view that ketone bodies were toxic waste products. It happened
simply
because the only available test at that time detected 3-hydroxybutyrate
(which,
in fact, is not a ketone body at all but here it doesn't matter) in
diabetic urine. Acetone on the other hand is a ketone and is present in
blood and urine
when the plasma concentration of acetoacetate is elevated. The body
gets
rid of it through the lungs; this is where the sweet smell on the
breath during
ketosis comes from.
In 1967, the streamline health sciences
developed a so-called enzymatic
method of analysis of acetoacetate and 3-hydroxybutyrate, which led to
the
dramatic finding that the human brain, while in the condition of
prolonged
starvation, was able to use ketone bodies.
This finding triggered a reversal of the
negative opinion of ketosis as
a pathological and dangerous condition -- well, almost.
Many, if not most, dieticians and
nutritionists continue to warn dieters
against the dangerous consequences of ketosis. However, the facts
are:
(click
here
to continue)
Sources
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