Central Obesity & Dementia
Diet, Vitamin D, Calcium & Colon Cancer
"A critical weekly review of important new research findings for health-conscious readers..."
Last Updated: 10/5/2008
CENTRAL
OBESITY &
DEMENTIA
We are, quite
plainly, the heaviest society
in the recorded history of mankind.
More
than 60% of adult Americans are overweight, and one-fourth of the
There is ample
clinical evidence showing that
obesity is associated with an increased risk of high blood pressure
(hypertension), diabetes, heart disease, stroke, arthritis and
premature
death. Some cancers
also appear to be
more common among obese patents, including cancers of the breast,
pancreas,
esophagus, stomach, colon, rectum, uterus and kidney.
Although
generalized obesity is a risk factor
for all of the life-threatening diseases that I have described, the
accumulation of excess body fat within and around the abdomen (central
obesity)
appears to be linked with an especially high risk of obesity-associated
illnesses. Now, a
new research study, just published in
the journal Neurology, suggests
that
dementia may also be more common among patients with central obesity. This study was conducted
by the Kaiser
Permanente Division of Research in
In this study,
more than 6,500 patients
within the Kaiser Permanente Northern California system participated in
this
study. Between 1964
and 1973, these
patients had their abdominal diameters measured (sagittal abdominal
diameter),
and were then followed, for an average of 36 years, through clinical
records of
their subsequent visits for medical care at Kaiser Permanente
healthcare
facilities. In
addition to the incidence
of dementia in this large group of patients, the researchers also
considered
the following patient factors: gender, age, ethnic background, level of
formal
education, marital status, and the presence or absence of diabetes,
hypertension, elevated cholesterol (hyperlipidemia), stroke and heart
disease.
Out of the
approximately 6,600 patients
evaluated in this long-term study, 1,049 (16%) were ultimately
diagnosed with
dementia. When
these patients with
dementia were further analyzed, it was determined that the patients
with the
greatest abdominal diameter had nearly 3 times the risk of developing
dementia
when compared to patients with the smallest abdominal diameter. Because both diabetes and
hypertension also increase
the risk of dementia, the researchers in this study adjusted their
analysis to
account for these two other dementia risk factors.
However, following this adjustment, the nearly
three-fold incidence of dementia associated with central obesity
persisted.
To summarize, this
long-term analysis of a
very large group of patients enrolled in a comprehensive healthcare
maintenance
organization (HMO) appeared to show that central obesity was, by itself, a significant risk factor for
dementia. As this
study was not designed
to assess the mechanism, or mechanisms, whereby central obesity might
be
increasing the risk of dementia, it will be necessary to follow-up the
findings
of this study with a more focused clinical research trial in order to
gain a
better understanding of how central obesity affects the risk of
dementia. However,
the results of this study offer
additional and compelling data that obesity, and central obesity in
particular,
appears to be associated with an increased risk of dementia, in
addition to the
increased risk of other life-threatening illnesses that have previously
been
identified.
DIET, VITAMIN D, CALCIUM
& COLON CANCER
Regular readers of
this column already know
that I have a very strong interest in disease prevention, particularly
through
lifestyle modifications. These
modifiable
lifestyle factors include, principally, diet, natural products and
dietary
supplements, and physical activity levels.
It has been estimated by cancer epidemiology experts that
somewhere
between 60 and 80% of all cancers could be eliminated through
relatively
moderate lifestyle modifications, although this conclusion receives
shockingly
little emphasis within our current healthcare system.
(A forthcoming book of mine, “A Cancer
Prevention Guide for the Human Race,” extensively covers the currently
available scientific and clinical evidence supporting specific
lifestyle
modifications that appear to reduce the risk of the most common causes
of
cancer-related death.)
The scientific
evidence related to dietary
factors and colorectal cancer risk remains a bit unclear at the present
time. Indeed, some
recent research
studies have called into question a few longstanding and conventional
assumptions about diet and colorectal cancer risk.
For example, for decades, we’ve been telling
our patients that a high-fiber diet will reduce their risk of
developing
colorectal cancer. However,
recently
published clinical research has suggested that there may not be a
significant
relationship between the amount of fiber in your diet and the risk of
developing pre-cancerous polyps (adenomas) of the colon and rectum. To complicate matters
further, however, other
recent clinical studies have suggested that at least certain types of
dietary
fiber may actually reduce the risk
of
adenoma formation in the colon and rectum.
So, the jury would appear to still be out on the issue of
dietary fiber
as a possible colorectal cancer prevention strategy (although there are
many
other documented health benefits to eating a diet rich in natural
high-fiber
foods!).
The role of
Vitamin D and calcium in
preventing colorectal cancer has also been an area of intense study,
lately. Once again,
as is unfortunately often the
case with clinical research, there is a considerable amount of
contradictory
research data with respect to the effectiveness, if any, of Vitamin D
and
calcium in the prevention of colorectal cancer.
However, several high quality epidemiological studies in
recent years
have suggested at least a moderate protective effect against colorectal
cancer
associated with higher levels of Vitamin D and calcium in the blood
(blood
levels of calcium are primarily controlled by Vitamin D, in the diet,
and
parathyroid hormone, which is secreted by small glands located near the
thyroid
gland in the neck).
A newly published
research study in the
journal Cancer Research takes a
further look at potentially adverse health effects associated with the
typical highly-processed,
high-fat, low-fiber “western diet.” (Most
nutrition experts consider the typical western diet to be deficient in
fruits
and vegetables, fiber, and other important nutrients, including Vitamin
D and
calcium.) This
study was conducted by
researchers at
In this study,
laboratory mice were fed the
“rodent-equivalent” of a western diet for most of their lifespan (an
average of
2 years). The
researchers noted that a long-term
western diet was associated with an increased risk of colon tumors in
these
mice, when compared to mice that were fed standard “mouse chow.” Seeking to learn more
about the exact causes
of the observed increase in colon tumors associated with a prolonged
western
diet, the scientists then supplemented the western diet of these
laboratory
mice with individual nutrients known to be deficient in the human
western diet.
When the
researchers added Vitamin D and
calcium supplements, the increased incidence of colon cancer previously
observed in the mice that received the western diet essentially
disappeared. However,
supplements of fiber, folate
(Vitamin B-9), choline and
methionine, all of which are deficient in the human western diet,
failed to
reverse the increased incidence of colon cancer observed in these
laboratory
mice that were fed a western diet.
The scientists
then studied the function of
genes known to be associated with the development of colorectal cancer. Specifically, the effects
of a prolonged
western diet on these cancer-associated genes were evaluated, and with
rather
startling findings. Gene
expression
studies revealed that a prolonged western diet, in laboratory mice, was
associated
with changes in cancer-associated gene function that is more typically
observed
in patients who inherit a gene mutation (the APC gene) that is
associated with
a very high risk of developing a hereditary form of colorectal cancer. Among those mice that
received supplements of
Vitamin D and calcium, in addition to a western diet, these
cancer-associated
genetic changes were not observed
in
the cells lining the animals’ colons.
To briefly
summarize, an animal model of
colon cancer was developed in this research study, using laboratory
mice that
were fed a “western-diet-equivalent” throughout most of their lifespan. The animals placed on a
western diet experienced
an increased incidence of colon tumors, although Vitamin D and calcium
supplements appeared to reverse this increased risk.
At the level of genetic changes known to be
associated with colorectal cancer development, a western diet appeared
to be
associated with a high level of cancer-associated changes in gene
expression. Once
again, however, these cancer-associated
genetic changes appeared to be prevented by adding Vitamin D and
calcium supplements
to the animals’ diet.
A few caveats
before you run out to the
drugstore and load up on Vitamin D and calcium pills.
First, as always, it is important to remember
that what works in laboratory mice and rats doesn’t always carry over
to human
physiology. There
have been numerous
research studies of treatments that have shown dramatic effects in
laboratory
animals, but have then gone on to fail in human clinical trials. So, this animal study,
including the
cancer-associated gene expression studies, will have to be replicated
in human
clinical studies before the findings of the animal study can be
confirmed in
humans as well. Secondly,
there have already
been several human studies that have looked at blood levels of Vitamin
D and
calcium, as well as clinical studies that incorporated supplements of
these
nutrients. Some of
these studies have
shown no apparent protective effects against colorectal cancer by these
nutrients, while other studies have shown a modest-to-moderate
protective
effect, at best.
On the whole, a
considerable number of
well-designed and well-executed human clinical research studies suggest
that
vitamin D and calcium may have a modest-to-moderate protective effect
against
colorectal cancer. However,
none of these human studies have
shown as
dramatic a protective effect with Vitamin D and calcium as was observed
in this
laboratory animal study. Once
again, the
methodology used in this animal study will need to be translated into a
human
clinical trial before anyone can definitively say that Vitamin D and
calcium
supplements are highly effective in the prevention of colorectal cancer. For now, however, it is
prudent to ensure
that your diet is at least sufficient in these two very important
nutrients.
Disclaimer:
As always, my advice to readers is to seek the advice of your physician
before making any significant changes in
medications, diet, or level of physical activity.
Dr. Wascher is an oncologic surgeon, professor of surgery, a widely published author, and the Director of the Division of Surgical Oncology at Newark Beth Israel Medical Center
http://www.sbhcs.com/hospitals/newark_beth_israel/mservices/oncology/surgical.html
Send your feedback to Dr. Wascher at
rwascher@doctorwascher.net
Links to Other Health & Wellness Sites
Copyright 2008. Robert A. Wascher, MD, FACS. All rights reserved.
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