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Living
exacts a toll on us all. There is fossil evidence of arthritic-like
conditions in some dinosaurs. Sharks, rats, humans and other species get
cancer. But by and large, most nonhuman mammals are spared high blood
pressure, heart disease, diabetes, obesity, and similar conditions
collectively referred to as "the diseases of civilization." (See U.S.
Health Statistics box below) Why? Is it because they do not
live as long as humans? Not necessarily, as some species are relatively
long-lived. Some species of tortoises can live nearly two hundreds of years,
as do some fish. But they are not genetically close to us. What of our
evolutionary cousins and siblings? In the wild, chimpanzees live to on
average about 35-40 years. This lifespan matched or exceeded that of our
forbearers for countless millennia, but was surpassed by humans during the
past 60 years or so. This, most scientists concede, is attributable to
improved nutrition and disease prevention and treatment. So it would seem
that we are doing better than our evolutionary relatives on the whole. But
are we really?
Let’s turn this question around. Does hypertension, heart disease, diabetes,
and other chronic conditions appear in chimpanzees who reach middle age and
advanced age? While some diseases such as cancer do occur in ageing chimps,
the rates appear to be far lower than one would expect if just the ageing
process alone were the culprit. All things considered, the “diseases of
civilization” occur at remarkably low rates in our aged evolutionary
relatives. The “why” behind this health discrepancy between chimps and humans
should, in all probability, hold the key to our collective quest for maximal
health and longevity.
In chimps and other nonhuman animals, diet and physical activity patterns are
basically in harmony with each species evolved nature. In short, taking our
evolutionary siblings as an example, chimpanzees eat and engage in patterns
of physical exertion that are consistent with very ancient and entrenched
patterns. Humans, on the other hand, have deviated greatly from the dietary
and health-conducive physical activity that characterized our particular
branch of the primate family tree for hundreds of thousands of years.
During the course of the past forty years or so evidence has steadily accrued
indicating that humans achieve and maintain optimal health on a diet that
consists largely of protein, specific complex carbohydrates, and certain
fats. Indeed, the dietary pattern that anthropologists and various nutrition
expects have found is most consonant with our evolved nature is one referred
to as “Paleolithic” or “Old Stone Age.” It is one few people in the West follow today. And it is this mismatch
between our ancient metabolic machinery and relatively recent dietary patterns,
i.e., food intake patterns that rose during the last 10,000 years (Neolithic
or “New Stone Age” to present) that many experts feel underlies the rise and
proliferation of many chronic diseases.
But aren’t we living longer and healthier?
At the turn of the last century, the average American woman could expect to
live to be about 51 years of age. The average man could expect to blow out at
least 48 candles on his cake before being visited by the Grim Reaper.
By 1998 these averages had grown considerably. Women can now expect to live
to be80 years old, and men 74 years old (Most recent confirmation: CDC
statistics, 2002).
According to government public health sources, these gains in the American
life span are the result, at least in part, of reductions in infant
mortality, infectious diseases among infants and children, and such basic
public health measures as safer drinking water, widespread vaccination
programs, better nutrition, and an improved standard of living. Other players
include improved screening and treatment of certain cancers, declines in
tobacco use among adults, and improvements in the medical management of many
chronic diseases.
We are indisputably living longer. But -- and this is a big BUT -- there is
plenty of room for improvement.
Americans are on-the-whole overweight and out-of-shape. Researchers have
linked obesity and a lack of exercise to the development of adult onset
diabetes, heart disease, many forms of cancers, and to high blood pressure.
Today, heart disease, cancer and stroke are the leading causes of death among
adults in the United
States. Diseases of civilization.
Diseases whose development and course are, many scientists tell us, slowed or
otherwise beneficially impacted by dietary, nutritional, and exercise factors.
So yes, we really do need to enhance our dietary, nutritional, and
exercise patterns in the USA.
Which brings us to the question of the mechanics of change. We read almost
daily newspaper articles on the health benefits of specific foods, beverages,
fitness pursuits, and such. And yet, swimming in information though we are,
the polls indicate that maybe only about 3% of Americans actually act on what
they know.
Is this attributable to laziness or simply information overload or both? Or
maybe it is that other concerns crowd out doing what we know is best.
Grabbing a burger at a corner fast food place makes it possible to eat and
get back to work in 30 minutes time. Or maybe we have just come to expect
instant answers in what has become an age of instant foods, instant online
access to information, and instant gratification.
Then, too, we are by-and-large inveterate gamblers insofar as we have a
tendency to think the guy down the street will not get away with his or her
unhealthy lifestyle choices, but we will.
If you think in terms of your own life, you probably see many of the these
factors at play. Human nature being what it is, most of us prefer
convenience, speed, and comfort over working at staying well and fit.
In light of this, a compromise of sorts would seem in order. Which is to say,
we need to zero in on simple, relatively easy to make changes that will help
us maximize our health and quality of life. But do such simple but effective
measures exist?
• Simple changes that confer rich health dividends.
Medical researchers are increasingly finding that significant health benefits
including disease prevention result from relatively simple dietary and
nutritional changes combined with low time investment, low impact physical
activities. Let’s take a look a at a few you can readily and easily introduce
into your particular lifestyle. The western diet is by-and-large too high in
fat. And with cause: We humans like, yes, even crave fat. Sugary
things too. This ancient pattern is wired into our brains. In a word, early
people needed energy to stay healthy and survive. Fats and sugars are to us
what Ever Ready™ batteries are to the perpetual motion bunny on TV.
We are, according to many anthropologists, modern folk running about with
"Stone Age” brains. We are adapted to seek out fatty foods and sweet
stuff, and it is a preference, a deep-seated craving if you will, that isn't
easily surmounted or tamed.
And perhaps it shouldn't be. Consider:
In a study carried out involving people on the tropical island
of Kitava in Papua New Guinea,
researchers surveyed 2300 natives aged 20-96 with respect to heart disease
patterns
(1).
These are so-called "primitive" people who get a lot of their daily
calories from fat. In a nutshell, the scientists found that sudden cardiac
death and stroke were extremely rare in Kitavans. All the adults surveyed had
blood pressure readings lower than average westerners, and were relatively
thin. Interestingly, serum cholesterol were a little high, probably due to
the Kitavans high intake of saturated fat from coconuts.
The diet of the Kitavans, you ask? Tubers, fruit, fish and coconuts mainly.
Little western food or alcohol. Saturated fat intake from coconut was high,
as was their intake of omega 3 polyunsaturated fatty acids, soluble fiber,
and minerals. Salt intake was quite low compared to levels in the West.
As for physical activity, the Kitavans were found to be slightly more
physically active than sedentary western populations. Eighty per cent of both
sexes were daily smokers. Other published research underscores what was seen
in the Kitavans.
So does fat play a role in the genesis of heart disease or not?
Here we have a population eating a lot of fat, smoking, and being only
slightly more active than westerners, and they are thinner, have a lower
average resting blood pressure than most of us, and virtually no heart
disease. So what's protecting the Kitavans? What are they doing that we in
the U.S.
and elsewhere are not?
Well, while there is as of yet no clear consensus among scientists, there is
sufficient evidence to indicate that the kind of fats consumed is a
key player in the development heart disease. In a word, Westerners eat too
much of the artery-clogging fats like trans fatty acids -- the
"bad" fat in stick margarine -- as well as saturated fat.
But wait a minute, the Kitavans eat lots of saturated fat, have higher
serum cholesterol levels than most Westerners, and yet have almost no
cardiovascular disease. What gives?
The verdict isn't in, but the protective factor appears to be the high levels
of omega-3 fatty acids in the "Stone Age" diet of the Kitavans.
This is the main fat in cold water fish that has been shown to protect people
from developing blood vessel blockage.
So why isn't the Kitavan's smoking wrecking havoc in their arteries? Again,
the answer appears to lie in the amounts of omega-3 fatty acid-rich food the
Kitavans consume daily. These fatty acids protect cell membranes from
incurring the sort of damage that appears to favor the development of heart
disease and even some cancers.
In Japan,
where 59% of men smoke, ..that's right, a whopping 59% according to CDC
statistics published during 1996,......lung cancer rates are lower than what
one would expect. Many epidemiologists and other researchers feel that the
Japanese penchant for eating lots of omega-3 rich suchi, sushimi, and such
underlies this trend.
No, this is not to say that it is OK to smoke. Smokers consuming high levels
of omega-3 fatty acids still get cancer.
What this body of evidence suggests in terms of fleshing out a "balanced
diet" is this: When the daily fat bug bites, satiate it with the health
protective fats. Instead of chowing down on foods rich in saturated or trans
fatty acids, make a practice of eating omega-3 rich fish such as lake trout,
tuna, and salmon, and monounsaturated fat-rich foods such as olives,
flaxseed, and peanut oils, and avocados.
Peanuts, walnuts, and wheat germ are good sources of omega-3 rich fatty
acids, by the way.
If you do not happen to favor fish, omega-3 rich fish oil capsules can be
found at most health food stores and even many pharmacies. Please note that
diabetics and people on blood thinners should discuss fish oil supplements
with a physician, as they can exacerbate or complicate these conditions.
• What exactly is a balanced diet?
The term “a balanced diet” was mentioned above. So what goes into making a
balanced diet? And what exactly is a balanced diet anyway?
Briefly, a balanced diet is one in which you eat a varied enough intake of
foods to furnish your body with the vitamins and minerals it needs to avoid
deficiencies of same, as well as prevent certain chronic diseases like adult
onset diabetes and heart disease. Dietary needs vary according to life stage,
your lifestyle, and particular health pedigree, so to speak.
The experts suggest that we select food from 5 major food groups: each day.
These are:
Vegetables
Fruits
Breads, cereals, rice, and pasta
Milk, yogurt, and cheese
and
Meat, poultry, fish, dry beans, eggs, and nuts.
Since breads, cereals, rice, pasta, beans, milk, yogurt, and cheese were
introduced into the human diet during the past 10,000 years or so, some
anthropologists and health care professionals feel that we are not really
adapted to consuming them. Our metabolic machinery, if you will, is much
older and is geared to thrive on a diet high in protein, low in sodium but
high in potassium, and high in fruit and certain vegetables.
There is a growing body of evidence which indicates that a balanced diet lies
in adopting a paleolithic or so-called "Stone Age" diet. Proponents
point to the fact that many of the more recent dietary add on such as wheat,
beans, and milk evoke allergic reactions in many people. Milk proteins have
been implicated in the onset of juvenile diabetes.
(2.)
On the other hand, peoples who eat a so-called "primitive diet",
one high in protein, complex carbohydrates such as potassium rich fruit, but
low or devoid of beans, potatoes, rice, cereals, and milk, typically have few
of the chronic diseases that plague Western societies. Interestingly, this
kind of "primitive diet" is high in the powerful antioxidant
compound alpha lipoic acid, as well as those B-vitamins that reduce elevated
homocysteine levels (Homocysteine is a sulfur-containing amino acid that is
produced during normal metabolic activity in the body and which, in high enough
amounts, contributes to the development of cardiovascular disease.)
All in all, while still controversial, it does make sense that a diet
consistent with our evolved nature is probably going to produce more health
benefits than a diet at odds with this nature. Recent scientific studies
appear to be bearing this out. For example, in a 14-year study involving more
than 80,000 women, scientists at Harvard
Medical School
discovered that women with the highest protein intakes were 26 percent less
likely than those who ate the least protein to develop ischemic heart disease
(IHD).
(3.)
More importantly, protein-rich diets benefited these women regardless
of their fat intake.
Until a consensus emerges from all the studies, it is probably wise to give
credence to the government's dietary guidelines. However, in line with the
evidence discussed in this article, we should strive to include lots of
choices rich in omega-3 fatty acids.
(4.)
• Herbs that may help keep disease at bay
Given the fact that the leading causes of death in adults are heart disease,
cancer, and stroke, we will consider some herbs that will prevent or
otherwise impact these conditions. Of course, as was true of the suggestion
that folks eat more omega-3 rich fish, the herbs introduced will for the most
part involve simple additions to your basic dietary and supplement use
patterns.
Heart Disease (Arterial Blockage), Hypertension & Stroke
The first thing we will briefly look at is common herbs that impact the
players in artery disease, especially vessel blockage with plague. Since
plague-narrowed arteries can lead to hypertension, heart attack, and stroke,
we will, so to speak, be knocking off 3 bad birds with one herbal volley!
The first herb we will consider is cayenne, also known as hot red pepper.
Several scientific studies have been carried out in which it was found that
cayenne lowers artery-clogging cholesterol and triglycerides.
In Thailand,
medical researchers took particular note of the fact that people who consume
fairly large quantities of cayenne or hot red pepper have a lower incidence
of potentially dangerous blood clots (called thromoembolisms). Intrigued, the
scientists surveyed medical records of people in countries where hot spicy
foods are regularly consumed, and found that folks who eat a diet high in
cayenne have a much lower incidence of blood clotting diseases.
(5.)
This is logical, given the fact that cayenne contains compounds that have
fibrinolytic activity, meaning they are able to break up blood clots.
Working cayenne into one's diet is, of course, relatively easy. Just begin
seasoning food with cayenne. Some cayenne-savvy folks carry a small bottle of
hot red pepper with them to work and even to restaurants, and just sprinkle
it on various foods during the course of their day.
Supermarkets carry plenty of foods laced with hot red pepper, and it is
fairly easy to locate a Mexican restaurant in most metropolitan cities
throughout the world.
Garlic may also help fight arterial blockage in many ways. Various studies
have found that garlic does such things as protect against free radicals,
reduce the tendency of the blood to clot, and possibly lower both blood
pressure and cholesterol levels. In at least one published study, garlic was
found to raise patient levels of the artery protective lipid, HDL -- High
Density Lipoproteins.
(6.)
The yellow spice Tumeric, used in curry dishes, has also shown effectiveness
in terms of lowering cholesterol.
While you are chowing down on that hot red pepper, garlic, and tumeric dish,
you will no doubt want or actually need something to wash down your
spicy load. This brings us to the 2nd easily introduced dietary measure to
help prevent or retard arterial blockage: Tea.
Black, white and green teas contain compounds called polyphenols that lower
cholesterol and triglyceride levels, as well as flavinoids that prevent the
artery-blocking cholesterol, LDL, from undergoing significant oxidation. If
you are not acquainted with oxidation, leave a pat of butter out at room
temperature for a few weeks. It will go rancid due to the oxidation process.
During 1989, I carried out a pilot medical study (at the Steenblock Medical
Clinic, El Toro, California USA) involving the effects of a Chinese black tea
variety called Yunnan Tuocha on patients with high serum
cholesterol levels. This group of patients drank one cup of the tea with
meals and did not change their diet or lifestyle at all. Those who
consistently drank the tea experienced an average drop in total cholesterol
of 19.33% after one month.
One note of warning: If you are taking an MAO inhibitor, the caffeine in
green tea could cause problems. Also, if you are taking a blood-thinning drug
such as warfarin, please be advised that large amounts of green tea could
interfere with its effectiveness, because green tea contains vitamin K, which
directly counteracts warfarin's blood-thinning action.
Cancer
A lot of very compelling research being done on foods and herbs that are
known as "chemopreventative compounds";, i.e., food and supplement
items that prevent cancer. Among the more promising are green tea, Karawatake
and possibly reischi mushrooms, ginseng, garlic and soy. We will take a
cursory look at green tea, ginseng, and garlic.
Green tea, as most of your probably know, is one of the most popular
beverages in Asia, where it has been used as
a medical purposes and disease prevention for over 4,000 years. Many
researchers feel that green tea contributes to the relatively low incidence
of stomach cancer in certain areas of Japan.
The most bioactive compound in green tea is called epigallocatechin gallate
or EGCG, which has been found to inhibit cancer development. During 1992, a
study was published in which medical scientists reported that EGCG inhibits
the "promotion stage" of chemical carcinogenesis in the liver.
The consensus among many scientists is that green tea, or more specifically
EGCG, is a potent cancer prevention agent.
A recent observational study on ginseng indicates it may exert a
chemopreventative effect. The study in question was carried out in South Korea
and involved keeping track of 4,587 men and women aged 39 years and older
from 1987 to 1991. People who regularly used or rank Panax ginseng
were compared with individuals matched in terms of sex, age, .alcohol use,
smoking, education and economic status who did not use ginseng.
(7.)
The results were impressive. Those who used ginseng showed a 60% decrease in
risk
However, it should be noted that a great deal of controversy surrounds this
study. For one thing, it was reported that persons who used ginseng less than
three times per year experienced a 54% reduction in risk. It seems unlikely
that occasional use of ginseng could reduce cancer mortality by more than
half! Even so, this study may point to some "smoke in the
woodpile". Given that ginseng has shown immune boosting properties in
many studies, it's use as a cancer prevention tool seems warranted.
Garlic is another ancient herb that looks promising as a chemopreventative
agent. Allicin, the principal active chemical ingredient in garlic, boasts a
number of benefits, including cancer prevention. In a July 1997 press release
from the Mercy Cancer Institute of Pittsburgh, laboratory tests indicated
that garlic could help to slow the growth of tumors, as well as inhibit their
formation in the bladder and breast. A West Virginia University
study found that oral application of allium sativum inhibited the growth of
tumors and reduced mortality in lab mice with bladder cancer. It should be
pointed out that garlic compounds have also shown antimutagenic properties,
which means it protects cells from incurring genetic changes that set the
stage for cancer. Many scientists feel that specific sulfur compounds in
garlic both inhibit cancer and suppress tumor cells. Supportive evidence of
this comes from the Shandong Province in China, where stomach cancer
morality risk was found to be 13 times lower in those folks who ingested 20
grams of garlic daily than in those who consumed only one gram daily.
Working green tea, ginseng, and garlic into the average person's diet is
relatively easy and inexpensive. Green tea and ginseng are widely available
in tea bag, powder, and tea bag forms. Garlic can be found in grocery stores
everywhere.
EXERCISE
Humankind evolved in an environment where physical agility, stamina, and
fitness paid rich dividends in terms of survival and leaving behind viable
offspring. Accordingly, physical exercise would be expected to have a
positive impact on both our physical health and even mood -- and it does. For
example, intense activity along the lines of aerobic exercise has been found
to improve the cardiovascular system, muscle strength and flexibility. It
also tends to increase artery size and elasticity, prevent plague build-up in
circulatory vessels, and prevent blood clots. Regular exercise has been shown
to boost HDL (good) cholesterol levels, and lower both total cholesterol and
blood pressure. The lungs, too, benefit insofar as physical exertion and
exercise enhance ability to breathe deeply, easily and efficiently. Exercise
burns fat and often alleviates stress.
According to experts, one should engage in vigorous activity such as fast
walking, bicycling, jogging, swimming or doing aerobic exercises for at least
30 minutes, three times weekly. For those over 35 years of age, as well as
those have been sedentary for a long time who have (or suspect they might
have) a medical condition, it would be wise to consult a physician concerning
the kinds of exercise that will not compromise one's health.
Exercise need not be regimented or ritualized, although many folks probably
do better on a program that requires adherence to a routine. In light of the
fact that health benefits have been documented from low impact activities
like just walking 30 minutes or so per week (Recall the Kitavans!), many
“vehicle-dependent” folks would do well to park their machines and take to
foot. Here in Japan
where I live, daily physical exertion is part of life. Most people, for
example, use trains to get to and from work or school, which requires
negotiating stairs and train platforms. This consistent, moderate physical
activity may be part of the reason the Japanese have a very long life span
(82 years for men, 84 years for women). In the U.S., where cars are virtually
considered a necessity, physically taxing activity is minimized and a great
many wind up proverbial couch potatoes. Turning the tables need not involve
grueling, boringly repetitive exercise but, rather, may be as simple as doing
by choice what the Japanese do by “design”: Walk, climb, and move about.
Concluding Remarks
People today are generally living longer, but many are struggling with
chronic illnesses and health challenges such as cardiovascular disease and
adult onset diabetes. Diseases of civilization. Many are linked to the
wear and tear associated with a long life, while unhealthy dietary choices, a
lack of exercise, stress, and a multitude of other players give rise to or
contribute to others. As you’ve read, a growing body of scientific evidence
indicates that people in societies where diet and exercise patterns mirror
those of our “Stone Age” ancestors have few, if any of these maladies. This
strongly suggests that we can circumvent or ameliorate many of them by simply
bringing our lifestyles into harmony with our evolved nature.
Readers interested in learning more about the “Stone Age” diet are urged to
acquire and peruse Dr. Loren Cordain’s excellent book, “The Paleo Diet: Lose
Weight and Get Healthy by Eating the Food You Were Designed to Eat.” Also
recommended is “The Paleo Diet web site”, which sports a wealth of material,
both popular and scientific. The URL is: http://www.panix.com/~paleodiet/
__________________________________________________________________________
Recommended Supplemental Reading
Online article: Cave Men Diets Offer Insights To Today's Health Problems,
Study Shows, 2/5/2002, http://www.sciencedaily.com/releases/2002/02/020205080142.htm
Book: “The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You
Were Designed to Eat” by Loren Cordain, Ph.D.
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U. S. Health Statistics
Leading Causes of Death
(All figures are for U.S.)
Final 2000 data
Ten Leading Causes of Death in the U.S.:
Heart Disease: 710,760
Cancer: 553,091
Stroke: 167661
Chronic Lower Respiratory Disease: 122,009
Accidents: 97,900
Diabetes: 69,301
Pneumonia/Influenza: 65,313
Alzheimer's Disease: 49,558
Nephritis, nephrotic syndrome, and nephrosis: 37,251
Septicemia: 31,224
Source: National Vital Statistics Report, Vol. 50, No. 16
DIABETES
(All figures are for U.S.)
Deaths Annually: 69,301 (2000)
Age-Adjusted Death Rate: 25.2 deaths per 100,000 population (2000)
Cause of Death Rank: 6 (2000)
Source: National Vital Statistics Reports, Vol. 50, No. 16
Number of Americans With Diabetes: 10 million (1997)
Source: Vital and Health Statistics Series 10, No. 205
Heart Disease
(All figures are for U.S.)
Deaths Annually: 709,894 (2000)
Age-Adjusted Death Rate: 257.9 deaths per 100,000 population (2000)
Cause of Death Rank: 1 (2000)
Source: National Vital Statistics Reports, Vol. 49, No. 12
Hypertension
(All figures are for U.S.)
Percent of Americans Ages 20-74 With Hypertension: 23% (1988-94)
Hypertension Is Most Prevalent in the Black Population
Over Three-Quarters of Women Aged 75 and Over Have Hypertension
Sixty-four Percent of Men Aged 75 and Over Have Hypertension
Source: Health, United States, 2002 Table 68
Deaths Annually: 17,964 (2000)
Death Rate: 6.5 deaths per 100,000 population (2000)
Source: National Vital Statistics Reports, Vol.49, No. 12
Overweight Prevalence
(All figures are for U.S.)
Sixty-four percent of U.S. Adults are overweight or obese. (1999-2000)
Twenty-three percent of U.S. Adults are obese (BMI greater than or equal to
30.0). (1999-2000)
Percent of Adolescents (ages 12-19) Who Are Overweight: 15% (1999-2000)
Percent of Children (ages 6-11) Who Are Overweight: 15% (1999-2000)
Source: Health-E Stat
Source for statistics and facts in this table:
CDC - National Center for Health Statistics
http://www.cdc.gov/nchs/fastats/Default.htm
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References
· (1.) Lindeberg S. Apparent absence of
cerebrocardiovascular disease in Melanesians. Risk factors and nutritional
considerations - the Kitava Study [M.D. Ph.D.]. University of Lund,
1994. (Go to: “On the Benefits of Ancient Diets”, http://www.paleodiet.com/lindeberg/)
· (2.)Monetini L, Cavallo MG, Manfrini S,
Stefanini L, Picarelli A, Di Tola M, Petrone A, Bianchi M, La Presa M, Di
Giulio C, Baroni MG, Thorpe R, Walker BK, IMDIAB Group, Pozzilli P.,
‘Antibodies to bovine Beta-casein in diabetes and other autoimmune diseases,’
Horm Metab Res 2002 Aug;34(8):455-9.
· (3.) Hu, Frank B., et. al., "Dietary
protein and risk of ischemic heart disease in American women." Journal
of Clinical Nutrition, Vol. 70 No. 2, 221-227, August 1999.
· (4.) Nestel, Paul et al. “The n-3 fatty
acids eicosapentaenoic acid and docosahexaenoic acid increase systemic
arterial compliance in humans.” Am J Clin Nutr 2002;76:326-30.
· (5.) Visudhiphan S, Poolsuppasit S,
Pibolnukarintr O, et. al. “The relationship between high fibrinolytic
activity and daily capsicum ingestion in Thais.” Am J Clin Nutr.
1982;35:1452-1458.
· (6.) Silagy C, Neil A. Garlic as a lipid
lowering agent: a meta-analysis. J Royal Coll Phys London 1994; 28(1): 39-45.
· (7.) Int J Epidemiol. 1998. 27. 359-364
___________________________________________________________________Dr. Payne
can be reached by e-mail at biotheoretician@gmail.com
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