| Low
Carb Diet- Part 2
by Sam Torontour B.Sc., C.S.C.S. |
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The mainstream medical
community has been opposed to low-carbohydrate dietary
protocols since their onset. Their opposition involves
four main concerns:
1. high fat/low carbohydrate protocols and the threat
of heart disease. |
2. high fat/low carbohydrate protocols and ketoacidosis.
3. high protein/low carbohydrate protocols and osteoporosis.
4. high protein/low carbohydrate protocols and nitrogen
stress. The most obvious concern involves low carbohydrate/high
fat/high protein dietary protocols, in which individuals
drastically reduce their carbohydrate intake in favor
of fats and proteins. The medical community is concerned
about the potential threat that a higher fat diet might
pose for cardiovascular diseases, and rightfully so.
However, proper balancing of the different types of dietary
fats can go a long way to preventing coronary heart disease,
and also in promoting good cardiovascular health. Here
are five of the most commonly consumed types of fats.
Those that are solid at room temperature, like butter
and animal fat, are called saturated fats. Those that
are liquid at room temperature (oils) fall into two categories:
monounsaturated fats (ie.from olive oil, peanut oil, canola
oil and avocados) and polyunsaturated fats (ie.omega-3
- from fish oil and walnut oil, omega-6 - from nut oils
and certain vegetable oils). There are also the tropical
oils, which are saturated fats that are solid or semi-solid
at room temperature.
Finally, trans fats are those which have been artificially
hydrogenated and thus converted from unsaturated into
saturated fats. Saturated fats pose an obvious risk as
far as heart disease is concerned and should be kept to
a minimum. The American Heart Association recommends taking
in no more than 10% of one's total daily caloric intake
in the form of saturated fat.(18) On the other hand, mono
and poly unsaturated fats are considered to be a healthier
choice as far as heart disease is concerned. In fact the
AHA states that "Polyunsaturated fats tend to help
your body get rid of newly formed cholesterol. Thus, they
keep the blood cholesterol level down and reduce cholesterol
deposits in artery walls.
Recent research has shown that monounsaturated fats may
also help reduce blood cholesterol as long as the diet
is very low in saturated fat." (18) Another interesting
area that has recently been brought to public attention
concerns the omega-3 vs. omega-6 fats. Both omega-3 and
omega-6 fats are considered essential fats (ie. the body
can not manufacture these fats and thus depends on getting
them in the diet). However, they are not processed in
the same ways by the body, and their ultimate pathways
are somewhat antagonistic. Research involving Inuit populations
have shown a very low incidence of heart disease among
Inuits despite a diet very high in whale blubber (an obvious
saturated fat).
It seems that all the freshwater fish that is consumed
by the Inuit has a heart-protecting mechanism. As it turns
out, the Inuit diet, despite being very high in saturated
fat, is also very high in omega-3 fats found in freshwater
fish (especially salmon). It is believed that omega-3
fats predispose the body to less blood coagulation and
a lower inflammatory response, and thus less heart disease
forming activity (ie.plaque formation in arteries and
other cardiovascular diseases).
On the other hand, omega-6 fats are believed to lead to
greater rates of blood coagulation and a greater inflammatory
response, and are thought to be more of a factor for heart
disease. In general, omega-6 fats are much more abundant
than omega-3 fats in the average diet, and the average
person would be well-advised to consume foods that are
higher in omega-3 than omega-6 fats. An obvious dietary
adjustment involves simply eating more freshwater fish
(particularly salmon and trout). See Fig. 1 for a comparative
list.
Fig 1. Content of Omega-3 and Omega-6 Essential Fatty
Acids in Oils:
Approximate EFA content in grams per 100 grams:
Essential Fatty Acids in NUTS: Fig 2. Content of Omega-3
and Omega-6 Essential Fatty Acids in Nuts
Approximate EFA content in grams per 100 grams:
Essential Fatty Acids in SEEDS: Fig 3. Content of Omega-3
and Omega-6 Essential Fatty Acids in Seeds
Approximate EFA content in grams per 100 grams:
Tropical Oils are another interesting and somewhat
ambiguous topic that has been floating around for quite
some time. Included in this group are coconut oil, palm
kernal oil and the infamous modified palm kernal oil.
The tropical oils are interesting because although they
are saturated, they have properties which set them apart
from other saturated fats. The main difference is their
molecular length. The tropical oils consist of a type
of fat known as Medium-chain triglycerides (MCT), and
as this name implies, they are shorter than the usual
saturated fat. This allows them to be absorbed and used
differently than other fats. Apparently, MCT's bypass
hepatic circulation (the circulation of the liver) and
are absorbed intact directly into the blood through
the small intestine.
Once they have been absorbed, they are processed by
the liver and converted into a form that is used easily
for energy. With this in mind, it is logical to assume
that medium-chain triglycerides derived from tropical
oils may not linger in the blood for a long enough time
to pose a threat for heart disease.(3,4,5)
The AHA groups the Tropical Oils with other saturated
fats, and recommends to restrict their intake along
with other saturated fats. Other research points to
the fact that because they are processed differently
than other longer-chain fats, they do not pose a likely
threat for heart disease. Obviously, further research
in this area is nesessary.
Trans fats are another topic that has been floating
around the media lately. The word 'Trans' and it's counterpart
'Cis' refer to the specific molecular geometry of a
particular substance. Most substances adopt and maintain
a 'cis' geometry in their natural state. Fats are no
exception to this rule. There are, however, incidents
where a fat becomes artificially converted from a natural
'cis' geometry to an induced 'trans' geometry. One way
that this happens is when a fat undergoes the process
of Hydrogenation. In this process, an unsaturated fat
(a fat that is not completely bound up or 'saturated'
by hydrogen atoms) is heated and bombarded by hydrogen
atoms, and thus artificially 'Hydrogenated' and rendered
into a saturated fat. In this process, part of the newly-hydrogenated
fat molecule will adopt a 'Trans' molecular geometry.
It is these artificially induced 'trans' fats which
have stirred so much concern among the medical community
and the general public. This is because 'trans' fats
have been implicated in higher levels of low-density
lipoprotein (LDL or 'bad cholesterol')) and lower levels
of beneficial high-density lipoprotein (HDL or 'Good
Cholesterol'), and pose a greater risk for heart disease
than even saturated fats (saturated fats have not been
implicated in the lowering of HDL).(1,2)
Companies have been using hydrogenated 'trans' vegetable
oils in prepared and packaged foods for years because
they do not spoil easily, thereby increasing the product's
shelf-life. Besides the obvious issue of converting
an unsaturated fat into a saturated fat, of greater
interest is the fact that these fats are further altered
from their natural state and rendered even more unhealthy.
Modified palm kernal oil and margerine are both examples
of foods containing hydrogenated trans vegetable oils.
The bottom line on 'trans' fats: They are neither natural
nor good for us; consume as little as possible.
So, to minimize the risk of heart disease that may be
associated with low carbohydrate/high fat/high protein
dietary protocols, simply consume no more than 10% of
the total caloric intake in the form of saturated fats,
consume more omega-3 than omega-6 fats and consume little
or no 'trans' fats. Follow these guidelines, and the
risk of heart disease associated with high fat intake
can be greatly reduced.
However, heart disease is not the only health concern
associated with low carbohydrate/high fat/high protein
dietary protocols. Another criticism that the medical
community has made is that they are Ketogenic. Ketones
or Keto acids are normal intermediates in fat metabolism,
and their accumulation in the blood is normally tolerated
within specific levels. Beyond this, the accumulation
of ketones in the blood becomes toxic and potentially
lethal, as evidenced in diabetic individuals who can
suffer a diabetic coma and even death if their ketone
levels are not kept within tolerable boundaries.
Accumulation of ketones happens because of the absence
Pyruvic Acid. Pyruvic acid, supplied mainly by the breakdown
of glucose through the process of Glycolysis, converts
to a metabolite called Oxaloacetate. Oxaloacetate combines
with incoming fat that is in the process of being broken
down. Without it, fat metabolism will stop here. For
this reason it is said that fat burns in a carbohydrate
flame.
When fat breaks down, it forms 2-carbon units called
Acetyl compounds. These Acetyl compounds convert to
form Acetyl Coa, which combines with the Oxaloacetate
derived from pyruvic acid. The complex that is formed,
Citric Acid, then continues into the next stage of metabolism,
the Krebbs or Citric Acid cycle. In the absence of an
adequate supply of pyruvic acid, fat can not enter the
Krebbs Cycle, can not be processed beyond the stage
of Acetyl-CoA, and will convert to ketones. If the rate
of ketone production is greater than its removal in
the urine, then they will accumulate to intolerable
levels.
In normal individuals, pyruvic acid is easily obtained
from the breakdown of carbohydrates in food. In the
absence of dietary carbohydrates, the body can rely
on certain amino acids to make pyruvic acid, as well
as the gluconeogenic substances Lactic Acid and Glycerol.
These substances can replace glucose as a source of
pyruvic acid, and will prevent the accumulation of ketones,
but not entirely. Letting ketones accumulate is not
healthy, desirable or even comfortable. Any diet that
limits carbohydrate intake in favor of fats is certainly
going to lead to a state of ketone accumulation or Ketoacidosis.
Most people can not endure ketoacidosis for very long
and cheat by eating carbohydrates at some point.
Several diets prescribe decreasing carbohydrates and
increasing fats. Proponents of these so-called 'ketogenic'
diets purport that by chronically reducing carbohydrate
intake, somehow the body will become magically 'fat
adapted' and burn more fat. Apparently, after a brief
period of exposure to a low-carbohydrate protocol, we
are supposed to become more efficient at using fat as
a source of fuel. Physiologically speaking, this may
not be an accurate way of describing what happens.
The exact meaning and metabolic conditions associated
with being 'fat-adapted' are not entirely clear, and
in fact, not everyone experiences the same kind of 'fat-adaptation'.
For example, people who are in poor aerobic condition
and who are used to high levels of carbohydrates in
the diet (especially refined carbs) do not adapt easily
to high-fat dietary protocols.(16) One of the ways that
an individual might become 'fat-adapted' is by getting
used to the chronic state of ketoacidosis caused by
increasing fats and decreasing carbohydrates.
In general, there is no way of avoiding a ketoacidotic
state when dietary carbohydrates are restricted. This
is one of the pitfalls of a high fat/low carbohydrate
diet. In the short term, this is uncomfortable and in
the long-term it is unhealthy. This is why the medical
community has issues with this type of protocol, and
rightfully so. Even if you regulate the type of fats
in your diet, the inevitability of ketoacidosis renders
such protocols ineffective in the long-term, unhealthy
and ultimately dangerous.
One of the chief concerns that the medical community
has with low carbohydrate/high protein protocols involves
the possible risks associated with high protein intake
and bone loss. Initial studies showed that omnivores
had lower bone density than vegetarians (8,17) and that
Inuits, especially females, had significantly lower
bone density than Caucasians (11). These studies led
the medical community to believe that high protein intake
was responsible for bone demineralization.
Later and more sophisticated studies showed that the
source of protein is an important factor in the effect
of dietary protein on demineralization."When protein
is given as meat, subjects do not show any increase
in calcium excreted, or any significant change in serum
calcium, even over a long period." (13) Earlier
studies, using isolated, fractionated amino acids from
milk or eggs as a protein source showed that high protein
intake led to increased calcium loss (14).Other studies
showed that high protein intake increased absorbsion
of calcium when dietary intake of calcium was adequate
(10). Also, high intake of meat showed no long-term
adverse affects when compared with a normal intake of
meat. (15)
The final concern that the medical community has regarding
low carbohydrate/high protein protocols involves protein
balance and nitrogen stress. Presently, the RDA for
protein is 0.8 grams/kg body weight. If one were to
consume 30% of a 2000 Kcal/day diet in the form of protein
(as is prescribed in the zone protocol), that would
equate to a total of 150 grams of protein. That is nearly
3 times the RDA. The question is whether or not this
is a potentially a dangerous amount for an individual
to consume over the short term.
In the absence of dietary carbohydrates, the body will
use several non-glucose substances to make glucose (this
process is called Gluconeogenesis). Glucose is considered
an essential nutrient, and we have several ways to ensure
that our blood-glucose levels stay within their normal
range. By the process of gluconeogenesis, we can use
lactic acid, protein broken down to amino acids, and
glycerol derived from the breakdown of triglycerides,
all to make glucose.
In the process of converting to glucose, the nitrogen-containing
group (Amine group) is removed from the amino acid through
the process of deamination. The nitrogen waste product
is then excreted in the urine in the form of urea and
ammonia. This entire process is both taxing and energetically
unfavorable. In fact, there is a net loss of energy
resulting from the metabolic cost of converting amino
acids into glucose. Proponents of high-protein dietary
protocols claim that this net energy loss can contribute
to an overall energy deficit, and thus benefit weight-loss.
However, if the body is required to rely heavily on
protein to make glucose, besides placing an increased
stress on the liver and kidneys in terms of nitrogenous
waste, it will lead to a large amount of muscle wasting.
This loss of muscle can ultimately lead to a reduction
of overall energy expenditure and a slowing of the RMR.
Therefore, the net loss in energy resulting from gluconeogenesis
is greatly offset by muscle wasting.
In terms of nitrogen stress, the body is a fairly adaptable
machine, and the liver is fairly resilient and effective
as a detoxifying organ. It can handle a fair amount
of toxic stress and still maintain relative health.
It is possible to maintain a low carbohydrate/low fat/high
protein protocol long enough to lose fat, without enduring
any severe short-term or long-term health problems.
However, people who suffer from any disease of the liver
or kidneys should consult with a physician before making
any radical dietary adjustments. These are some of the
medical considerations that should be considered before
starting a low carb dietary protocol. In the next part
of this series, I will go into some of the hormonal
and metabolic considerations regaring low carb diets.
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Sam Torontour, B.Sc., C.S.C.S. is
an experienced personal trainer and certified strength
and conditioning specialist with over 15 years experience
as a fitness professional. With a Bachelor of Science
degree in Exercise Science and a minor in Biology
from Concordia University, he possesses a thorough
scientific understanding of the workings of the
human body, nutrition and exercise. |
| He is certified by the National Strength and Conditioning
Association (NSCA) as a Certified Strength and Conditioning
Specialist (CSCS) and has expertise in a wide variety
of areas. His specialties include physique transformation,
athletic preparation, muscle balance and posture,
flexibility, nutrition and supplementation. He is
also an instructor of Muay Thai (an ancient martial
art developed in Thailand). He has worked with males
and females of all ages and from all walks of life,
including students, older adults, teens and professionals.
He is presently working at Gym L’Apogée
on St. Laurent Boulevard in Montreal, and also works
with clients at their homes. |
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