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Dietary Chromium: An Overview
By Barry Mennen, M.D.
Executive Director, Chromium InformationBureau, Inc.
Definition and Function
Chromium is an element; that is, it is one of the basic building blocks
of all things, both living and non-living. And, like certain of the elements
such as carbon, nitrogen, iron and calcium (among others), chromium plays
an essential role in our life and health.
Chromium's function in our bodies is critical: without it, the hormone
insulin would not work. Most people are familiar with insulin as the shot
diabetics give themselves in order to control their high blood sugar.
But, what most people don't realize is that insulin is the "master
hormone" of our metabolism; it not only controls blood sugar levels
and many other aspects of carbohydrate breakdown and storage, but also
directs much of the metabolism involving fat, protein and energy (calories).
Because insulin requires chromium to function properly, this trace element
has significant biological effects in the body. (See below for more on
insulin)
Discovery of Chromium's Role in Human Health
It was known by the 1950s that chromium was required by animals to control
blood sugar, but it wasn't until the 1970s that chromium's essential role
in humans was clearly proven. This proof came accidentally, as a result
of a new procedure that had been introduced to nourish hospitalized patients
who could not take in any food by mouth. This procedure, giving specially-made
feeding solutions directly through the patient's vein, is referred to
as Total Parenteral Nutrition or TPN.
TPN was designed to give patients all the carbohydrates, proteins, fats,
vitamins and minerals they needed to maintain health until they could
once again eat normally and obtain these nutrients from food. Some of
these patients who had been fed intravenously for months developed high
blood sugars just as if they were diabetic (which they weren't). The doctors
then had to start insulin therapy in order to treat this diabetes-like
condition and even then the insulin they were given didn't appear to work
as well as it should have.
Since it was already known that chromium was necessary for insulin action,
it was thought that this trace element may have been lacking in these
patients' TPN solutions. Thus it was deduced that these patients were
showing signs of very severe chromium deficiency. The physicians caring
for them then added chromium in very small amounts less than 50 micrograms
(abbreviated as mcg; equal to 1/1000 of a milligram) to their IV feeding
solution and quickly noted an improvement.
The patients no longer required insulin injections, and their blood
sugars and other abnormalities returned to normal. After these cases of
chromium deficiency and its serious consequences were reported, medical
and nutrition experts agreed that chromium was an essential nutrient for
humans and advised health professionals administering TPN about the danger
of omitting chromium from the solutions.
Both the Food and Drug Administration (FDA) and the Food and Nutrition
Board of the National Research Council (the quasi-governmental body that
determines the Recommended Dietary Allowances or RDAs ) have therefore
designated chromium an essential nutritional trace element.
Although insulin mainly works in muscle, fat and the liver,this hormone
also exerts profound effects on many other body tissues. Insulin is the
primary hormone that controls how the body's cells absorb, use and store
nutrients and energy. Besides regulating the cellular absorption and utilization
of glucose, amino acids (the building blocks of protein) and fatty acids,
insulin also activates and inactivates enzymes (the protein catalysts
for the body's biochemical reactions) and directly affects certain genetic
processes including protein synthesis.
While trivalent chromium works with insulin to move glucose into cells,
we currently do not know how many other critical actions of insulin require
chromium to function. However, regarding the insulin-induced movement
of glucose into cells, it is likely that chromium is either involved with
the binding of insulin toits receptor (the site on the cell membrane which
responds to signals from biochemical messengers such as hormones, drugs
and nutrients and then stimulates or inhibits specific cellular functions)
or with certain of the reactions which take place after the initial receptor
site activation, reactions that are referred to as post-receptor events.
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Chromium and Diabetes
Because of chromium's connection to insulin function, it should come
as no surprise that most of the research with this trace mineral relates
to diabetes or to non-diabetic persons who develop high blood glucose
levels after ingesting simple sugar.There are at least 16 clinical studies
which have tested specific chromium compounds in such patients using proper
scientific methods (other studies on chromium supplementation in diabetics
which used questionable methods in their study design are not included
in the following summary).
While three of the 17 properly designed studies showed no benefit of
chromium supplementation in diabetics, 14 did showblood glucose improvements
in the patients tested. For example,a recent study that has been reported
(which was presented in1995 at the annual meeting of the American College
of Nutrition)showed dramatic improvements in blood sugar using less than
one milligram of supplemental chromium picolinate in a group of women
who developed gestational diabetes (that is, they showed symptoms and
signs of diabetes only during their pregnancies).
The latest study to examine the issue of chromium supplementation and
adult-onset diabetes was presented in June,1996 at the annual Scientific
Sessions of the American Diabetes Association held in San Francisco, CA.
Researchers from the Human Nutrition Research Center of the United States
Departmentof Agriculture collaborated with Chinese researchers from the
Beijing Medical University.
They randomized 180 adult-onset diabetics into 3 groups of 60 each:
one group received placebo twice per day, the second received 100 mcg
twice daily of chromium as chromium picolinate and the third received
500 mcg of chromium as chromium picolinate twice daily. Their blood work
was examined at baseline, at 2 months and at 4 months.
The patients were told to remain on their anti-diabetic medications
and continue with their diets and activity levels as before.
The results were impressive: blood glucose, insulin levels, cholesterol
and glycated hemoglobin (a measure of blood sugar control over the previous
few months) all decreased, with the higher dose generally (but not always)
more effective than the200 mcg.
How could such tiny amounts of chromium have such profound effects on
insulin's action? Again, the answer is not known with certainty, but the
evidence so far suggests that chromium strengthens certain effects of
insulin on the body's cells; in other words, it doesn't work by stimulating
the body to make more insulin, but rather chromium makes the insulin which
is present function more effectively in the cells of the body.
When the body does not respond to insulin in the normal manner, doctors
refer to this as insulin resistance. Insulin resistance signifies that
the insulin which is circulating in the blood is not able to have its
usual effects on various tissues in thebody. This is not the problem with
the type of diabetes (referred to as type I or juvenile-onset) that strikes
young children: these individuals cannot make insulin anymore and thusmust
take it by injection. However, most diabetics suffer from maturity-onset
diabetes (or type II; increasingly referred to as NIDDM or non-insulin
dependent diabetes mellitus; this type of diabetes affects 90% of people
with the disease).
It is these patients with NIDDM who demonstrate insulin resistance and
are the ones most at risk for chromium deficiency and its consequences.
Further, there is some evidence that marginal chromium deficiency may
be important in other areas of health and disease. These other diseases
where chromium may be important are some of the most common and significant
illnesses of industrialized nations (see below).
The following is the ending to the chapter on chromium nutrition in
the latest edition of the standard reference textbook on medical nutrition:
"Based on current knowledge of chromium function and nutrition.the
possibility cannot be ignored that inadequate chromium status may be responsible
in part for some cases of impaired glucose tolerance, 'hyperglycemia,
hypoglycemia, glycosuria [sugar in urine], and refractoriness to insulin."
Modern Nutrition in Health and Disease, Eighth Ed.., 1994.Shils, Olson
and Shike, eds.
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HEALTH NOTE
It is important to note that persons with diabetes who are on insulin
or other anti-diabetic medications should check with their doctors before
supplementing their diets. Because chromium may decrease the amount of
insulin resistance present, it may change the type or amount of medication
needed to treat the diabetes and/or the frequency with which blood sugar
monitoringneeds to be done.
This is especially important for those persons with diabetes who are
under tight blood glucose control. Adding supplemental chromium in this
situation has the potential to cause low blood sugar (hypoglycemia).
The Insulin Resistance Syndrome (Syndrome X; Reaven's Syndrome; Insulin-Metabolic
Syndrome)
The combination of obesity, diabetes, hypertension (high bloodpressure)
along with abnormalities in blood cholesterol and fat (lipid) has long
been noted in the medical literature. By the late 1980s, a noted diabetes
expert from Stanford University(Dr. Gerald Reaven) proposed that the basic
combination of highblood sugar, high blood pressure and abnormal blood
lipids all constituted disease that was based on increased insulin resistance;
he noted that while increased insulin resistance isthe first step in the
development of maturity-onset or type II diabetes, it is the body's response
to the insulin resistance which determines whether or not the individual
becomes a diabetic or not.
"Even if high blood sugar does not develop, insulin resistance
does not appear to be a good thing to have: The fact that an insulin-resistant
subject may not become diabetic does not meanthat they suffer no untoward
consequences. Indeed, an argumentcan be made that the more insulin sensitive
an individual, the better off he or she is, and that the attempt to compensate
for insulin resistance sets in motion a series of events that playan important
role in the development of both hypertension and coronary artery disease."
Reaven GM. Role of Insulin Resistance in Human Disease.Diabetes, 37:1595,
Dec., 1988.
Since chromium reduces insulin resistance, this essential trace element
could therefore have wide-ranging effects on high blood pressure and abnormal
blood lipids in addition to lowering blood sugar.
However, Dr. Reaven did not connect any insulin resistance to possible
marginal chromium status, and we cite him here only to point out his contribution
to describing this syndrome. It is also important to note that while studies
in peer-reviewed medical journals have shown that chromium supplementation
lowers blood lipids such as triglycerides, for now there are no human
data on chromium and blood pressure.
Chromium and Body Composition
Another area that is gaining more interest lately is the possible effect
of chromium on body composition; that is, how chromium affects the relative
amounts of lean body mass (mainly muscle) compared to the amount of body
fat. At present, there are positive results from studies with four separate
animal species supplemented with chromium picolinate: pigs, lambs, rats
and chickens. In all of these species, there were increases in muscle
mass and decreases in fat body mass. And, in the case of pigs, these findings
have been confirmed by several additional studies.
For humans, however, the evidence was not as clear until quiterecently.
In October, 1996 a study published in a peer-reviewed medical journal
looked at 154 slightly overweight individuals split into three groups
who were supplemented with either 200 mcg of chromium as the picolinate
compound, 400 mcg of chromiumas the picolinate compound or a placebo.
Previously, some human studies had shown either no effect, an effect
similar to that seen in animals (that is, reduction in fat and increase
in muscle) or an effect in women but not inmen. The main problem with
these older studies was that they had looked at very few individuals sometimes
as few as 12; so, while it appeared that chromium was having an effect
on body composition, since there were so few persons involved in thestudies
we could not be absolutely certain.
Further, some of the prior studies looked at young athletes (such as
college football players) who, because of their high degree of fitness
upon entering the study would not, in all likelihood, make the best subjects
in which to observe these changes.
This latest study examined average Americans in Texas who were given
no special instructions in diet or exercise just the chromium at either
dosage level or the placebo. The study was double-blind and randomized.
What these researchers found after the 72 days of the study was a statistically
significant difference in the chromium groups vs. the placebo group in
change of body composition index (BCI, a sum of the loss in body fat plus
the gain in muscle mass) loss of body fat and total weight loss.
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The authors conclude:
These data suggest that supplementation with chromium picolinate can
lead to significant improvements in body composition when aBCI [body composition
index] is used as the outcome criterionthat represents a sum of the net
gains in nonfat mass added to the sum of the net losses of body fat.
Kaats GR, Blum K, Fisher JA and Adelman JA. Effects of chromium picolinate
supplementation on body composition: A randomized, double-masked, placebo-controlled
study. Current Therapeutic Research, 57(10):747-765, Oct. 1996
While the mechanism of action whereby chromium has this apparent effect
is not known, it is interesting to note that therapies for diabetes that
increase insulin levels in the blood are associated with weight gain (insulin
injections and sulfonylureas such as Diabinese and Micronase) while therapiesthat
decrease insulin levels (such as Glucophage and the not-yet-released oral
agent troglitazone) are associated with no weight gain or even weight
loss. Since chromium supplementation has been associated with decreased
insulin levels, it is tempting to speculate that it is through this effect
(that is, decreasing insulin resistance withthe attendant drop in circulating
insulin) that chromium worksin altering body composition.
Dietary Intake of Chromium
Data from U. S. Government sources show that the great majority of Americans
get less chromium in their daily diets than the amount recommended by
nutrition experts (the RDA Committee recommends 50-200 mcg of chromium/day;
the vast majority of Americans get less than 50 mcg/day).
"In the majority of all chromium supplementation studies in the
United States, at least half the subjects with impaired glucose tolerance
improved upon chromium supplementation, suggesting that the lower ranges
of chromiumintake from typical U.S. diet are not optimal with regard to
chromium nutriture."
RDA 10th Edition 1989
Few foods are rich sources of chromium in the Western diet, the best
being organ meats, mushrooms, wheat germ, broccoli and processed meats.
It is theorized that Stone Age people ingested more chromium than modern
people because they regularly ate organ meats from the animals they hunted
(which contained higher levels chromium as well as other trace elements).
Not only did these early people likely have a higher chromium intake
than modern ones, but perhaps more important than their higher intakes,
it is most likely that they lost less chromiumin their urine than we do.
This is because Stone Agers did not ingest nearly as much simple sugars
as modern people and simple sugar intake causes chromium to be lost in
the urine. These ingested sugars (such as table sugar and products made
with it) bring insulin and chromium into the blood and cause chromium
tobe excreted in the urine after it's through working with the insulin
on the increase in blood sugar.
We Americans consume an average of 120 pounds of sugar per year from
all sources. Thus, we can conclude that for hundreds of thousands of years
of human evolution, our ancestors most likelytook in more and lost less
of this essential trace element than modern Americans.
Another interesting fact demonstrated in large numbers of people both
in the U.S. and the U.K.--is that chromium tissue levels inhumans decrease
over our lifetimes. In fact, the highest tissue levels of chromium are
found in newborns: they get chromium inthe womb across the placenta from
their mothers. There is also evidence that pregnancy depletes a woman's
chromium stores, which may be one reason that as a total population our
bodies show loss of chromium as we age.
From this evidence inadequate chromium intake, increased chromium losses,
decreasing chromium tissue levels as we age, improvement in blood sugar
insignificant numbers of diabetics and pre-diabetics with modest chromium
supplementation and widespread insulin resistance (25%of Americans have
some degree of insulin resistance, though only a portion of this insulin
malfunction appears to be due to chromium deficiency) experts in chromium
nutrition urge supplementation with small amounts of this trace element
on adaily basis.
These experts feel that chromium supplementation for diabetics should
take its place alongside the two other proven ways of decreasing insulin
resistance: low-fat, high complex-carbohydrate diets for weight loss/weight
maintenanceand regular exercise.
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Safety
It is extremely difficult to poison laboratory animals with oral chromium.
For example,cats fed 1,000 mg of trivalent chromium per day showed no
signs of toxicity (the equivalent daily dose for a 150 lb person would
be approximately 35,000 mg per day or3.5 million mcg per day. In terms
of the number of 200 mcg tablets, this would be 175,000 tablets per day
for a human.
On March 14, 1996, a safety study conducted by the U. S. Department
of Agriculture was presented at the Society of Toxicology's annual meeting.
This study looked at various supplemental doses (including none) of chromium
chloride and chromium picolinate fed to rats for 6 months, The highest
doses were equal to a human consuming 5,000 tablets of 200 micrograms
chromium picolinate. At regular intervals during the study the rats were
weighed and blood was taken for laboratory tests.
At the end of the study the livers and kidneys (organs that would have
the highest tissue levels of chromium) were examined under the microscope.
There were no differences in any of the measurements or examinations between
the various groups. The investigators were unaware ("blinded")
as to which group the animals were in when the measurements and evaluations
were performed.
The safety issue had been raised by a study published inDecember, 1995
which attempted to link chromosomal damage in the test tube to oral supplementation
of chromium picolinate. These researchers used cultured Chinese hamster
ovarian cancer cells to which they directly added unnaturally high amounts
of chromium compounds, including chromium picolinate. Some of these cells
showed chromosomal damage (clastogenic effects).
This was not particularly surprising, since this concentration directly
applied to these cells in a test tube was 3,000 times the blood level
of people who are ingesting chromium picolinate as supplements!
Very few essential minerals tested in this way would be found to be
without toxicity; for example, merely doubling the blood concentration
of the mineral calcium is fatal to humans. When tested by the Ames test
(a specific test for mutagenicity) for cancer-causing potential, chromium
picolinate was proven negative.
Again, the standard medical reference on nutrition:
"Trivalent chromium has such a low order of toxicity that deleterious
effects from excessive intake of this form of chromium do not occur readily.
Trivalent chromium becomes toxic only at extremely high amounts.- chromium
then acts as a gastric irritant rather than as a toxic element interfering
with essential metabolism or biochemistry."
Modern Nutrition In Health and Disease, Eighth Ed., 1994.Shils, Olson
and Shike, eds.
Assessment of Chromium Status
One of the main problems that has hindered a more widespread interest
and possible usage of chromium by the medical profession is the fact that
gauging whether or not someone is chromium deficient or not cannot easily
be done. The only generally accepted method for assessment ofchromium
status is to supplement an individual (who has abnormalities of either
blood sugar, cholesterol, triglycerides or all three) with the trace clement
and see if the laboratory values improve. If they do, then chromium insufficiency
is presumed. This is an expensive and cumbersome process (especially when
doing a glucose tolerance test).
Summary
Indications are that marginal deficiency of chromium, an essential trace
mineral, may be widespread in industrialized nations. Further, the consequences
of this deficiency may contribute to some of the manifestations of obesity,
diabetes, abnormal blood lipids, hypertension and coronary artery disease
in 20th century western society.
Although some of the above is speculative, it would seem prudent for
Americans to supplement their diets with small amounts of trivalent chromium
(for example, 200 mcg of chromium picolinate) since the benefits of supplementation
may be significant for certain individuals and the safety of this regimen
is well-supported by a large amount of data.
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Postscript: What do Doctors Think About This?
You may now be asking: Why haven't I heard about this? Do my friends
who are diabetics known about this? Does my doctor know anything about
this? These are reasonable questions, and there are several issues involved
in dealing with issues relating to the apparent lack of interest in chromium
for diabetics.
- Doctors have traditionally shied away from techniques involving nutritional
management of their patients
- There is still no reliable way to test individuals for chromium status
- The first few decades of chromium research was complicated by contamination
of the food or tissues being examined by significant amounts of chromium
from the environment (the use of stainless steel laboratory equipment,
for example). This resulted in confusing and contradictory results from
different research facilities. By the early 1980s, this problem was
resolved, however.
- The marketing of nutritional therapies to physicians and other health
professionals is not nearly as extensive as pharmaceutical marketing;
since profits from nutritional therapies are significantly smaller than
those from pharmaceuticals, supplement manufacturers cannot justify
the large capital outlays needed for the promotional and educational
materials for physicians. In addition, representatives of drug manufacturers
frequently call on physicians to present them with new research data
and samples of their products. Direct mail and advertising are other
means by which pharmaceutica lmanufacturers get important information
about their products to doctors. The same promotional and educational
budgets are not available in the nutritional area.
Copyright: The Chromium Information Bureau, Inc. March, 1966; revised,June,
1996 and November, 1996
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