Jean-Louis wrote:
>Carbohydrates and heart disease
[deleted text]
>> Mc Dougall: "Worldwide the lowest incidence of heart disease is found
>>where people eat the lowest cholesterol diets and also have the lowest
>> HDL-cholesterol levels (Lancet 2:367, 1981)"
>...The effect of a low fat diet is that all fractions of cholesterol go down, but
>the ratio TC/HDL (which is an independent risk factor) doesn't improve.
>Remark: the Lancet article also mentions some ratios HDL/TC. Africa:
>0.26-0.32, Europe: 0.20-0.28, Asia and Surinam: 0.15-0.22.
>We should mention that hunter-gatherers, despite eating on average more
>than 55% of their calories from meat, have low TC and ratio TC/HDL, and low
>incidence of heart disease. The main reasons are: high monounsaturated fat intake, low
>carbohydrates, high protein [Metabolism 1991;40:338-43] [Clin Invest Med
>1992;15:349-5] [Can J Cardiol 1995;11 (supp G):127G-31G], low ratio omega
>6/omega 3, no hydrogenated oils [Am J Public Health 1994;84: 722-24] [Am J
>Clin Nutr 1997;66:1006s-10], more exercise. The composition of farmed animals is
>indeed rather different from the composition of wild animals.
[deleted text]
Hi Jean-Louis ,
I have a special interest
on cholesterol levels and would like to make some comments on what you wrote
and then forward an conference at Cyberounds.com that I came across.
I my self have a 119 TC vs. 39 HDL, that is a high
(generally speaking) rate, and, as you said, likely to vegans. However LDL
is as low as 70. So I wonder whether that TC/HDL rate is
that much important on very low TC levels. As says in this conference below,
if one has a HDL lower then 50 has to check the LDL. If LDL is OK(<130),
then no worry at all Before I had started my
lowfat-lowsugar/vegan/antioxidant oriented diet, my levels where 230 TC, 39
HDL and 154 LDL...risky!!! So, what's changed were TC and LDL.
HDL supposedly (as I once read on a medical report) is responsable for
not "allowing" LDL to cross the arthery walls and be deposited inside the arthery tissue,
increasing atherome. If there is low LDL (lower then 130), there would be no
problem, no matter the rate TC/HDL. A non harmful cholesterol is
200, and for a 0.25 HDL/TC rate HDL should be >50 and LDL 'round 130.
Since LDL is an inference regarding HDL, TC, and triglicerides levels,
seems that a low TC , around 120-130 typicall for vegans and low fat/low
protein intakers, is quite ok , since there can not be space for a LDL
higher then 60-80, that is much lower than the 130 LDL highest desireable
level.
If other diets like hunters-gathers get lower rates TC/HDL, that does
not mean that necessarly that the rate is a risk factor when coming down to
very low TC.
I came across this conference at cyberounds that refers this stuff.
Might be of some interest to some of you.
I first selected the part that refers to this subject, and after pasted
the whole conference , since the URL needs a restricted registration:
http://www.cyberounds.com/conferences/nutrition/conferences/0997/conference.
html
Sorry everyone for this large Kb post.
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"Current Issues Related to Diet and Cardiovascular Disease"
Robert M. Russell, M.D. and Alice H. Lichtenstein, D. Sc.
*Educational Objectives*
Upon completion of this activity, the participant should be able to:
-Enumerate the appropriate course of action for a patient within each
category of blood total and HDL cholesterol levels.
-Evaluate positive and negative risk factors in a patient.
-Provide the parameters for a Step 1 and Step 2 diet.
"Here, too, there is no one risk factor that is more important than
another (see Table 2). Each risk factor is considered independently. First,
we classify individuals on the basis of their total cholesterol level (see
Table 1 for more detail). A person with a total cholesterol level of less
than 200 mg/dl is considered to be in the desirable range; between 200 and
239 mg/dl in the borderline high-risk range; and 240 mg/dl or above in the
high-risk range. Within each of those categories, the physician should
enumerate the number of risk factors the individual has. The significant
risk factors are: hypertension, family history of cardiovascular disease,
current cigarette smoker, hypertension, low HDL cholesterol, diabetes
mellitus (see Table 2 for more detail). Although not considered independent
risk factors, obesity and physical inactivity should also be taken into
consideration.
If an individual has two or more risk factors (Table 2), and they are in the
borderline high-risk range, then they are considered to be at higher risk
and they are treated as though they are in the high-risk range (Table 4).
For individuals with low HDL cholesterol or in the borderline-high or high
cholesterol categories, an individual should be evaluated on the basis of
LDL cholesterol levels (Table 5). This necessitates a fasting blood sample
be obtained for the accurate determination of blood triglyceride levels. LDL
cholesterol levels are calculated from these data. If LDL cholesterol levels
are below 130 mg/dl and the individual is free of CHD, a patient is
considered to be in the desirable category. If their LDL cholesterol levels
are between 130 and 159 mg/dl with less than two risk factors, they are
considered to be in the borderline high-risk range, and above 160 mg/dl or
130 to 159 mg/dl with two or more risk factors in the high-risk range are
considered to be in the desirable < a name="table6ret">category (Table 5).
Lastly, Table 6 lists the recommended treatment and target LDL cholesterol
levels on the basis of LDL cholesterol levels."
(COMPLETE CONFERENCE) :
Alice H. Lichtenstein, D. Sc., is an Associate Professor of Nutrition in the
School of Nutrition Science and Policy at Tufts, an Associate Professor of
Family Medicine, Community Health at Tufts University School of Medicine and
a Scientist I at the Jean Mayer Human Nutrition Research Center on Aging at
Tufts. She completed her undergraduate work at Cornell, holds masters
degrees in Nutrition from Pennsylvania State and Harvard and earned her
doctoral degree in Nutrition from Harvard. Her research investigates the
kinetic behavior of lipoprotein particles, predictive factors for changes in
blood lipids induced by diet in individuals, the impact of body weight
changes on blood lipids and the relationship of absolute levels of dietary
fat, in contrast to fatty acid composition of the diet, on plasma lipids.
Dr. Lichtenstein is on the Editorial Board of the Journal of Nutrition and
Atherosclerosis.
"Being Thin is Not Necessarily the Solution
RMR
Alice, we all read something new about dietary fat in the newspapers almost
daily. How important a factor is dietary fat intake in the development of
coronary artery disease? And, if a person has a high fat diet but stays
relatively thin, is that person at greater increased risk of developing
coronary artery disease, compared to a person who not only eats a lot of fat
but is, in fact, obese?
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AHL
You cannot really tell by looking at someone whether they are of a desirable
body weight or overweight; whether they are going to be specifically
susceptible to the amount of or type of fat in their diet; or what's their
risk of developing cardiovascular disease. Each person is different.
Initally, the best way to check this risk is to measure their blood lipid
levels (see Table 1 for more detail). Most physicians do this routinely. If
someone has blood cholesterol levels in the borderline-high (200-239 mg/dl)
or high range (> 240 mg/dl), we know from a dietary perspective that the
most important factor affecting blood cholesterol levels is the saturated
fat intake and, secondarily, dietary cholesterol.
As mentioned a moment ago, there is no single recommended course to follow
for every problem and every person. A separate risk assessment needs to be
done on each individual--determine how many risk factors a person has (Table
2) and then make some decision about how aggressively to treat the patient.
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Risk Factors Vary With the Individual, But They Do Add Up
RMR
Alice, you mentioned the various risk factors for coronary artery disease
and I wonder if you would list them in order of importance as a review and,
secondly, could you review the main sources of saturated fats in our diet
and the mechanism whereby saturated fats give rise to elevated cholesterol
levels?
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AHL
Here, too, there is no one risk factor that is more important than another
(see Table 2). Each risk factor is considered independently. First, we
classify individuals on the basis of their total cholesterol level (see
Table 1 for more detail). A person with a total cholesterol level of less
than 200 mg/dl is considered to be in the desirable range; between 200 and
239 mg/dl in the borderline high-risk range; and 240 mg/dl or above in the
high-risk range. Within each of those categories, the physician should
enumerate the number of risk factors the individual has. The significant
risk factors are: hypertension, family history of cardiovascular disease,
current cigarette smoker, hypertension, low HDL cholesterol, diabetes
mellitus (see Table 2 for more detail). Although not considered independent
risk factors, obesity and physical inactivity should also be taken into
consideration.
If an individual has two or more risk factors (Table 2), and they are in the
borderline high-risk range, then they are considered to be at higher risk
and they are treated as though they are in the high-risk range (Table 4).
For individuals with low HDL cholesterol or in the borderline-high or high
cholesterol categories, an individual should be evaluated on the basis of
LDL cholesterol levels (Table 5). This necessitates a fasting blood sample
be obtained for the accurate determination of blood triglyceride levels. LDL
cholesterol levels are calculated from these data. If LDL cholesterol levels
are below 130 mg/dl and the individual is free of CHD, a patient is
considered to be in the desirable category. If their LDL cholesterol levels
are between 130 and 159 mg/dl with less than two risk factors, they are
considered to be in the borderline high-risk range, and above 160 mg/dl or
130 to 159 mg/dl with two or more risk factors in the high-risk range are
considered to be in the desirable < a name="table6ret">category (Table 5).
Lastly, Table 6 lists the recommended treatment and target LDL cholesterol
levels on the basis of LDL cholesterol levels.
However, if an individual has two or more risk factors and they are in the
borderline high risk range, they are treated more aggressively, as though
they are in the high risk range.
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Major Sources Of Saturated Fat In The Diet
AHL
Before we talk about the major sources of saturated fat in the diet, I would
like to indicate that the American Heart Association (AHA) and the National
Cholesterol Education Program (NCEP) have issued recommeded guidelines for
the dietary treatment of hypercholesterolemia which are shown in Table 3.
The patient should be first counseled to follow a Step 1 diet, that is, to
decrease their total fat intake to < 30% of calories, saturated fat to 8-10%
of calories and cholesterol to < 300 mg/day. If a patient is already on a
Step 1 diet, or an acceptable response is not achieved, the patient should
be advised to follow a Step 2 diet by further decreasing their saturated fat
intake to < 7% of calories and their cholesterol intake to < 200 mg/day. For
this strategy to be effective, it usually requires the help of a registered
dietitian or other appropriately trained healthcare provider. Usually,
decreasing the total fat content of the diet is easier to do than decreasing
the saturated fat content. In order to decrease effectively the saturated
fat content, it is important to know its major sources. These include animal
fats such as meat and full fat dairy products and, depending on one's
tastes, a few selected plant oils (Table 7). The plant oils, frequently
termed tropical oils, include coconut oil, palm oil, palm kernel oil and
cocoa butter and contain a fair amount of saturated fat. However, they do
not tend to be used in high levels in the United States.
If an American patient is being counseled to decrease their saturated fat
intake, the focus should be on full fat dairy products and meat.
Fortunately, there is a whole variety of non-fat, reduced-fat and low-fat
dairy products that are now available. So, a simple substitution can be
made. To reduce the intake of saturated fat from meat, one should counsel
patients to use cuts of meats that are lowest in fat. This is best done by
suggesting the patient buy cuts of meat with the least amount of visible
fat; trim meat of excess fat; with poultry, remove the skin before eating;
and, of course, cut down on the size portion of meat actually consumed.
Unfortunately, nutrient labeling does not help too much regarding the fat
content of meat. Ground beef is now labeled with the percent by weight as
lean. The patient should be counseled to choose those packages having the
highest percent lean, hence the lowest percent fat. However, this can get
confusing because the percentages listed on these packages have nothing to
do with the percent of calories as fat listed on the nutrient label of
packaged foods.
The other potential source of animal fat can come from cooking, as
discretionary fat is added during food preparation. We recommend that
individuals switch from animal fats such as lard or butter to vegetable
oils.
Although there is a tremendous amount of evidence to indicate that saturated
fat is the major determinant of plasma cholesterol levels, the mechanism by
which that occurs is not clear. Blood cholesterol levels are determined by
the balance between the rate at which lipoproteins are synthesized and the
rate of which they are catabolized. Saturated fat has been implicated to
impact in both of those processes, increasing the rate of production and
decreasing the rate of catabolism of lipoproteins.
The other dietary factor which elevates blood cholesterol levels is dietary
cholesterol. Major sources of dietary cholesterol are eggs and animal fats
(both dairy and meat). By decreasing the consumption of animal fat, in
addition to saturated fat, dietary cholesterol intake should also decrease.
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Trans Fatty Acids -- Do They Help?
RMR
In the last couple of years there was quite a debate going on about trans
fatty acids and the importance of trans fatty acids as a critical dietary
factor resulting in increased coronary artery disease incidence. I believe
you took the position that this was an exaggerated concern and I wonder if
you could give us a little bit of background on this debate and tell us why
you feel that way you do.
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AHL
First, I think we should really talk about what trans fatty acids are. Trans
fatty acid is a shorthand term for a fatty acid that contains at least one
double bond in the trans configuration. The naturally occurring double bonds
or the predominantly occurring double bonds in fatty acids are in the cis
configuration, where the hydrogen atoms surrounding the double bond are all
on the same side. In the trans configuration, the hydrogen atoms are on the
opposite sides of the double bond (Figure 1). It gives the fatty acid a
different confirmation, whereas a cis double bond gives fatty acid chain a
kink or bend, a trans double bond results in a straight chain. In that way,
it is more similar to a saturated fatty acid.
Figure 1. Cis and trans configurations of fatty acids.
Why are fats hydrogenated and and where do they come from in the diet? Trans
fatty acids are hydrogenated to increase their stability and also to
increase their plasticity or consistency. One of the original reasons for
hydrogenating vegetable oil, which has predominantly unsaturated fatty
acids, was to produce products, such as margarine, that could easily be used
in place of butter which has predominantly saturated fatty acids.
The trans fatty acids also come from animal fat (dairy products and meat).
Formed during bacterial metabolism in the rumen of animals, they are
incorporated into the animal's tissues and milk. They provide relatively low
amounts of trans fatty acids compared to hydrogenated fat.
Trans fatty acids have been in the diet for a long time. One of their
effects, the increase in the levels of total and LDL cholesterol, was
already known, but the other effect on plasma cholesterol levels wasn't
suggested until 1990, with the publication of a pivotal paper(1) wherein the
authors suggested that trans fatty acids decreased HDL cholesterol levels.
It was also suggested at that time that Western diets contained significant
enough levels of trans fatty acids that the situation should be reassessed.
Since then, a number of studies have been done,(2) most quite consistent
with the early work showing that trans fatty acids increase total and LDL
cholesterol levels.
With regard to lowering HDL cholesterol levels, I think the data are far
less clear. Within the range that it is estimated to be consumed in the
United States, it does not appear that trans fatty intake has a significant
effect on HDL cholesterol levels. Nonetheless, I think it is important to
take them into consideration, and do so with an understanding that, if one
reduces the level of trans fatty acids in the diet, something else is going
to be substituted. I think this is where some of the confusion and arguments
in the scientific community have arisen.
Right now, the main sources of discretionary trans fatty acids are margarine
and prepared foods that use hydrogenated fat in the processing. If you
reduce their intake, you increase the saturated fat intake to a greater
extent which would probably not have a beneficial effect, for example,
substituting butter for stick margarine. On the other hand, if you
substitute a liquid oil or soft margarine for stick margarine, then you are
decreasing the trans fatty acid intake and increasing the unsaturated fat
intake. This would probably have a beneficial effect.
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The Omega 3 Fatty Acids -- Just Fish Oil?
RMR
Another fatty acid that has recently moved into the general lexicon are the
fish oils, rich in omega-3 fatty acids. Can you explain what the latest
thinking is on the importance of these fatty acids in preventing coronary
artery disease?
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AHL
Omega-3 fatty acids are long chain fatty acids and usually contain three or
more double bonds that come from marine products or some vegetable oils such
as soybean or canola. They have very little impact on blood cholesterol
levels. What they do have an impact on is plasma triglyceride levels,
especially in individuals that have elevated triglyceride levels. They tend
to bring elevated triglyceride levels down. This is particularly important
because there is an inverse correlation between plasma triglyceride levels
and HDL cholesterol levels. If the triglyceride levels are brought down in
hypertriglyceridemic subjects, then the HDL cholesterol levels usually come
up.
Now, there is a certain amount of data suggesting that fish consumption will
decrease the risk of developing cardiovascular disease, although it is not
consistent. The mechanism is probably not via lowering blood cholesterol
levels or even triglyceride levels but through independent effects of
omega-3 fatty acids on blood pressure and platelet aggregation (decreasing
the risk of thrombosis). The increased use of fish as an entree may displace
high saturated fat meat from the diet, having the advantage of providing the
independent effects of omega-3 fatty acids and decreasing the saturated fat
intake.
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Exercise, Alcohol and Lower Cholesterol
RMR
With regard to HDL, we have heard that exercise can increase HDL levels. At
least somewhat and recently, there have been epidemiology studies indicating
that higher vitamin C levels in the diet and moderate -- one or two drinks a
day -- (as opposed to none or large amounts) of alcohol intake are
correlated with higher HDL levels. Are there intervention studies that
clearly show this and should medical professionals work to modify patients'
diets in some ways to "optimize" HDL levels?
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AHL
As opposed to LDL cholesterol levels and saturated fat, the evidence to
suggest that individuals who exercise or consume moderate amounts of alcohol
may have higher HDL cholesterol levels is a little more difficult to assess.
On the other hand, there are other reasons, in addition to HDL cholesterol
levels, that one would encourage moderate, not excessive, alcohol intake and
regular exercise. Epidemiological data suggest a negative association
between moderate alcohol use and risk of CHD. A half hour of exercise a day
is important for energy balance, which itself impacts on hypertension,
hyperlipidemia, decreased HDL cholesterol levels and diabetes mellitus.
The association of HDL levels and vitamin C is weaker. However, diets or
dietary patterns that tend to be high in vitamin A tend also to be high in
fruits and vegetables (and antioxidant vitamins) and lower in total fat,
saturated fat and cholesterol. So I think to argue just from the perspective
of increasing HDL cholesterol levels and vitamin C is a little difficult for
an individual patient. However, to encourage a prudent diet and active
lifestyle, independent of their effect of blood cholesterol level, will
probably be beneficial with respect to reducing one's risk of developing
cardiovascular disease.
(continues on 2/2)
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