Diseases Linked to Obesity and Insulin Resistance:
The Link Between Sugar Consumption and Cardiovascular Health
By
Fred Pescatore, MD
In this
continuing series, we are exploring the role obesity and improper eating habits
play in our health. In our last installment, we laid out the groundwork and
some definitions of obesity to make it easier to move forward in the
discussion. In this week’s session, the link between sugar and heart health – a
serious implication for anyone with diabetes will be examined.
The link between increased sugar consumption and
declining cardiovascular health has been known since the 1960’s and had been
proven to be a definite cause of cardiovascular morbidity and mortality. That
simply means that a diet filled with sugar will cause more heart disease and
more deaths due to heart disease. Unfortunately, little has been done with that
information and a high sugar/ high simple carbohydrate diet has been and
continues to be touted as the healthiest and the one recommended to patients by
their doctors.
Cardiovascular disease is the leading cause of
death of men in this country. However, once a woman’s menopause occurs, the
estrogen effect no longer occurs and the risk of heart disease in women begins
to escalate. This phenomenon is important because of the rapid rise in older
people in our patient population. Because of this, recently, there has been
much research to investigate the role of a high sugar diet in women.
Studies such as the Iowa Women’s Health Study and
the Nurses Health Study showed that women who consumed diets with a high
glycemic load had a higher cardiac heart disease risk. Those who consumed diets
with the highest glycemic load showed a 2 fold risk of heart disease. In the
Nurses Health Study, the analysis was controlled for total energy intake and
other dietary and non-dietary risk factors; therefore, identical caloric diets
were examined – the only difference was the macronutrient content of the meal.
Glycemic index and glycemic load are two terms
that must be understood in order to have a proper understanding of the role of
insulin resistance in cardiovascular disease, asthma, and diabetes. A glycemic
load is defined as the increased blood glucose excursions associated with an
intake of highly processed starches and sweets. It basically refers to a diet
that consists of the ingestion of many foods that have a high glycemic index.
Quite simply, what will your blood sugar do given a certain number of grams of
sugar – whether that sugar is in the form of sugar, or a simple carbohydrate
that is easily metabolized by the body as sugar?
The glycemic index is a measure of the rise in
glucose induced by ingestion of a carbohydrate. Foods that contain refined
sugars make a major contribution to glycemic load; other contributors include
refined starches, such as white bread and rice. The glycemic index measures
individual foods and does not take them together as a meal. There are numerous
glycemic index tables of common foods. It is an arbitrary designation with white
bread usually given the number 100. Anything metabolized more slowly by the
body is assigned a number lower and anything metabolized more quickly, is
assigned a higher number.
Let me cite a few examples because this concept
is hard for many people to understand. Pretzels for example are 107 on the
scale and are therefore metabolized more quickly than white bread. This is the
main reason why I consider pretzels not to be a health food, but rather
an un-health food. Ice cream for instance has a glycemic index around 37; and
is metabolized more slowly. That is not to say that ice cream is a food that
should be encouraged. The fat content of a particular food will also play a
role in the assigned glycemic index. Therefore, macronutrient content of an
entire meal needs to be evaluated.
Postprandial hyperglycemia has recently been
recognized to be an independent risk factor for cardiovascular disease, not only
in diabetics. Hyperglycemia was shown to have a 1.6 times increase in
cardiovascular disease in people with increased 2 hour blood sugar levels
because these glycemic spikes have been shown to cause arterial wall
thickening.
Furthermore, hyperglycemia can lead to an
increased amount of oxidative stress on the body. This oxidative stress appears
to play a role in increasing cardiovascular disease risk too. Increased glucose
loads causes oxidation of membrane lipids, proteins, lipoproteins, and activates
inflammation. It also lowers anti-oxidant concentrations and is associated with
increased blood pressure, accelerated clot formation, and reduced blood flow –
all things that lead to stroke.
A high glycemic index diet (someone who eats a
lot of foods that are sugars or simple carbohydrates) may also affect the risk
for cardiovascular disease by increasing insulin levels up to 2 fold when
compared to a similar caloric diet with a lower glycemic index. Therefore, when
calorie counts are equal, those who eat a diet with higher amounts of sugar will
increase their risk for cardiovascular disease simply because they are producing
more insulin in their bodies.
This condition, known as hyper-insulinemia is
believed to mediate, in part, the increased risk of heart disease associated
with Syndrome X, the insulin resistance syndrome. It does this through
independent effects on blood pressure, serum lipids, coagulation factors,
inflammatory mediators and endothelial function. The odds of developing
ischemic heart disease increase by 60% with increasing fasting insulin levels.
Overweight and obese adults have been shown to
have reduced myocardial vasoreactivity (their vessels don’t respond
appropriately). Insulin has more of a role in the body than just bringing down
blood sugar. This hormone, among other things, helps to enhance blood sugar
entry into the cells and how well our blood vessels respond to blood flow.
Insulin-induced enhancement of this flow is blunted in overweight and obese
individuals. Therefore, insulin plays an important regulatory role not only in
blood sugar but in blood flow as well – all cardiovascular effects.
Another thing to keep in mind is the basic
premise that insulin is a storage hormone. It causes our bodies to store any
excess energy that we ingest as triglycerides and fat. A diet that causes high
release of insulin is therefore going to make us gain weight. Any diet that
promotes a high carbohydrate, low fat approach is ultimately, by its very
nature, going to cause a higher release of insulin than a higher protein diet;
and therefore, a diet that will fail in the long run because it does not take
this insulin storage effect into account.
Another component that must be examined in
linking overweight and obesity to cardiovascular disease is the role that sugar
and hence the glycemic index plays on plasma lipoproteins. A number of studies
link dietary sugar with adverse changes in cholesterol lipoproteins. Several
studies have shown an inverse association between dietary sucrose and HDL –
which means as consumption goes up, HDL comes down. HDL, or high density
lipoprotein, is the cardio-protective cholesterol. Therefore, a higher HDL
level is something to be desired.
Still other studies show that a diet high in
sucrose (defined as greater than 20% of caloric intake – which is what most
people in this country eat) is associated with an elevation of plasma
triglyceride concentrations. This increase is due to both increased hepatic
secretion and impaired clearance of VLDL, very low density lipoprotein. This is
a grave situation as increased triglyceride levels are also associated with
increased risk of stroke and death. Triglycerides are a much more important
indicator of cardio-vascular health and should be watched closely as they can
trigger atherosclerotic plaque formation. High triglyceride levels are
especially ominous in diabetics as it increases their risk for pancreatitis, a
sometimes deadly and almost always damaging condition.
In summary, it has been shown that in those who
ingest lower glycemic index diets; that is, those diets lower in sugar and
simple carbohydrates; one finds higher HDL levels, lower triglyceride levels and
lower heart attack rates compared to those with the highest glycemic indexed
diets.
Considering that there is a way to reduce multiple risk factors for cardiovascular disease without the use of potentially harmful medications, it is important that they be considered. Dietary change and dietary control is a necessary and vital component to any health program, especially one aimed at the diabetic population. In our next installment, we will look more closely into certain dietary habits that can have a profound effect on blood sugar control and cardiovascular risk reduction. We will also examine some of the more important new blood test and how to interpret them.
Source: Diabetes In Control Dot Com: Thin Is Good.
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