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KETOSIS AND INSULIN SYNTHESIS
What is normal?
At the heart of the debate about most low carbohydrate diets are fundamental
questions about what is a "normal" diet and how the human body is
supposed to operate. These questions can be summarized as follows. Nutritive
carbohydrates (starches and sugars) in the diet tend to break down very easily
into glucose in the bloodstream (blood sugar) when consumed. Glucose in the
blood is used by the cells in the body for energy for their basic function.
Excessive amounts of glucose in the blood are toxic to the human body (the
reason diabetes causes such serious health problems)[citation needed]. In general,
unless a meal is very low in starches and sugars the level of glucose will
tend to rise to potentially dangerous levels[citation needed]. When this occurs,
the pancreas automatically produces insulin to cause the liver to convert glucose
into glycogen (glycogenesis) and triglycerides (which can become body fat),
thus reducing the blood sugars to safe levels. Diets with a high starch/sugar
content, therefore, cause sharp spikes in insulin production. As such the blood
sugar levels are highly variable with every meal.
By contrast, if the diet is very low in starches and sugars (low-carbohydrate
diets) the blood sugar level can fall so low that there is insufficient glucose
to fuel the cells in the body. This state causes the pancreas to produce glucagon.
Glucagon causes the conversion of stored glycogen to glucose and, once the
glycogen stores are exhausted, causes the liver to synthesize ketones (ketosis)
and glucose (gluconeogenesis) from fats and proteins, respectively. Most cells
in the body can use ketones for energy instead of glucose, and since ketones
are easier to produce, only a small amount of glucose is created (in other
words, ketosis is the more significant process in this case). Because diets
low in starches and sugars do not tend to directly affect blood sugar levels
significantly, meals tend to have little direct effect on insulin levels (and
so such diets tend to discourage insulin production in general).
The diets of most people in modern, so-called western nations, especially
the United States contain significant amounts of starches (and, frequently,
significant
amounts of sugars). As such, the metabolisms of most westerners tend to operate
outside of ketosis and tend to involve significant insulin production. This
has been regarded by medical science in the last century as being "normal." Ketosis
has generally been regarded as a dangerous (potentially life-threatening) state
which unnecessarily stresses the liver and causes destruction of muscle tissues.
The view that has been developed is that getting energy more from protein than
carbohydrates causes liver damage and that getting energy more from fats than
carbohydrates causes heart disease. This view is still the view of the majority
in the medical and nutritional science communities.
Most advocates of low-carbohydrate diets (specifically those that recommend
diets similar to the Atkins Diet) argue that this metabolic state (using primarily
blood glucose for energy) is not normal at all and that the human body is,
in fact, supposed to function primarily in ketosis. They argue that high insulin
levels can, in fact, cause many health problems, most significantly, fat storage
and weight gain. They argue that the purported dangers of ketosis are unsubstantiated
(some of the arguments against ketosis result from confusion between ketosis
and ketoacidosis which is a related but very different process). They also
argue that fat in the diet only contributes to heart disease in the presence
of high insulin levels and that if the diet is instead adjusted to induce ketosis,
fat and cholesterol in the diet are not a major concern (although most do not
advocate unrestricted fat intake and do advocate avoiding trans fat). Further,
whereas insulin in the bloodstream causes storage of food energy, when the
body is in ketosis, excess ketones (which contain excess energy) are excreted
in the urine and the breath.
Some argue, on this basis, that the ketogenic low-carbohydrate diets offer
a metabolic advantage, in that the body automatically eliminates food energy
that it does not need even with a high-energy diet. This argument has not yet
been demonstrated in clinical studies; one 2006 study done by the American
Journal of clinical nutrition, failed to find such an advantage over non-ketogenic
low-carb diets.
Their
Objective: We compared weight loss and biomarker change in adults
adhering to a ketogenic low-carbohydrate (KLC) diet or a nonketogenic
low-carbohydrate (NLC) diet.
Their Conclusions: KLC and NLC diets were
equally effective in reducing body weight and insulin resistance, but
the KLC diet was associated with several adverse metabolic and emotional
effects. The use of ketogenic diets for weight loss is not warranted.
Click here for
the full article.
This debate is on-going and no consensus currently exists.
http://en.wikipedia.org/wiki/Low-carbohydrate_diet#_note-13
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