Overview
Chromium is a mineral the body needs in very small amounts, but it plays a
significant role in human nutrition. Chromium’s most important function in the
body is to help regulate the amount of glucose (sugar) in the blood. Insulin
plays a starring role in this fundamental biological process by regulating the
movement of glucose from the blood and into cells.
Scientists believe that insulin uses chromium as an assistant
(technically, a cofactor) to “unlock the door” to the cell membrane, allowing
glucose to enter the cell. In the past, it was believed that to accomplish this
the body first converted chromium into a large chemical called glucose tolerance
factor (GTF). Intact GTF was thought to be present in certain foods, such as
brewer’s yeast, and for that reason such products were described as superior
sources of chromium. However, subsequent investigation indicated that researchers
were actually creating GTF inadvertently during the process of chemical analysis.
Scientists now believe that there is no such thing as GTF. Rather, chromium
appears to act in concert with a very small protein called low molecular weight
chromium-binding substance (LMWCr) to assist insulin’s action. LMWCr does not
permanently bind chromium and is not a likely source of chromium in foods.
Based on chromium’s close relationship with insulin, this trace mineral has
been studied as a treatment for diabetes. The results have been
somewhat positive: It seems fairly likely that chromium supplements can improve
blood sugar control in people with diabetes. Chromium also might be helpful for
milder abnormalities in blood sugar metabolism. One study suggests that chromium
might aid in weight loss too, but other studies failed to find this effect.
Requirements and Sources
The official U.S. recommendations for daily intake of chromium (in micrograms) are as follows: infants to six months (0.2) and seven to twelve months of age (5.5); children one to three years (11) and four to eight years (15); girls age nine to thirteen years (21) and fourteen to eighteen years (24); boys age nine to thirteen years (25); males age fourteen to fifty years (35); women age nineteen to fifty years (25), men age fifty-one and older (30), women age fifty-one and older (20), pregnant girls (29), pregnant women (30), nursing girls (44) and nursing women (45).
Some evidence suggests that chromium deficiency may be relatively common. However, this has not been proven, and the matter is greatly complicated because a good test to identify chromium deficiency is not available.
Severe chromium deficiency has been seen only in hospitalized persons receiving nutrition intravenously. Symptoms include problems with blood sugar control that cannot be corrected by insulin alone.
Corticosteroid treatment may cause increased chromium loss in the urine. It is possible that this loss of chromium may contribute to corticosteroid-induced diabetes.
Chromium is found in drinking water, especially hard water, but concentrations vary widely. Many good sources of chromium, such as whole wheat, are depleted of this important mineral during processing. The most concentrated sources of chromium are brewer’s yeast (not nutritional or torula yeast) and calf liver. Two ounces of brewer’s yeast or four ounces of calf liver supply between 50 and 60 micrograms (mcg) of chromium. Other good sources of chromium are whole grains, beer, and cheese. Also, calcium carbonate interferes with the absorption of chromium.
Therapeutic Dosages
The dosage of chromium used in studies ranges from 200 to 1,000 mcg daily, mostly in the form of chromium picolinate. However, there may be potential risks in the higher dosages of chromium. These and all other dosages of chromium cite the amount of the actual chromium ion in the supplement (“elemental chromium”), discounting the weight of the substances, such as picolinate, attached to it.
Some products state that they contain “GTF chromium.” Some of these products are manufactured from brewer’s yeast, which was once thought to contain GTF. Others contain chromium as chromium nicotinate, which bears a faint resemblance to the proposed GTF molecule. However, because GTF is no longer believed to exist, this claim should be disregarded.
Therapeutic Uses
Chromium has principally been studied for its possible benefits in improving blood sugar control in people with diabetes. Several studies suggest that people with type 2 diabetes may show some improvement when given appropriate dosages of chromium. One study suggests that chromium may also be useful for diabetes that occurs during pregnancy. In addition, nondiabetic persons with mildly impaired blood sugar control might attain better control of blood sugar with chromium supplementation. Because mild impairment of blood sugar control is believed to increase the risk of heart disease, chromium supplementation might help reduce heart disease rates.
Chromium has been sold as a “fat burner” and is also said to help build muscle tissue. However, most studies evaluating chromium’s ability to promote weight loss have not found benefits. One study failed to find benefit with a combination of chromium and conjugated linoleic acid. Studies evaluating chromium as a performance enhancer or aid to bodybuilding have yielded almost entirely negative results.
Studies on whether chromium can improve cholesterol levels have returned mixed
results. However, one study suggests that chromium combined with grape seed
extract might have a beneficial effect. In addition, among persons taking
beta-blockers, chromium may raise levels of HDL (good)
cholesterol.
When depression is characterized by rapid mood changes, excessive
sleeping and eating, a sense of leaden paralysis, and extreme sensitivity to
negative life events, the condition is called atypical depression. A small
(fifteen participants) double-blind, placebo-controlled study found that chromium
picolinate might be helpful for this form of depression; however, a much larger
study failed to find statistically significant benefits.
According to some researchers, impaired blood sugar control, high cholesterol,
weight gain, and high blood pressure are all part of a larger condition called
metabolic
syndrome, or syndrome X. Because chromium may be helpful for
the first three of these conditions, chromium deficiency has been proposed as the
cause of syndrome X. However, this has not been proven.
One study failed to find that chromium picolinate at 200 mcg per day can improve symptoms of polycystic ovaries, which is a common cause of infertility. Chromium has also been proposed as a treatment for acne, migraine headaches, and psoriasis, but there is no real evidence that it works for these conditions.
Scientific Evidence
Diabetes. The evidence regarding use of chromium for type 2 diabetes and other forms of diabetes remains incomplete and inconsistent. In a double-blind, placebo-controlled study, 180 people with type 2 diabetes were given placebo, 200 mcg of chromium picolinate, or 1,000 mcg chromium picolinate daily. The results showed that HbA1c values (a measure of long-term blood sugar control) improved significantly after two months in the group receiving 1,000 mcg and in both chromium groups after four months. Fasting glucose (a measure of short-term blood sugar control) was also lower in the group taking the higher dose of chromium.
A double-blind trial of seventy-eight people with type 2 diabetes compared two forms of chromium (brewer’s yeast and chromium chloride) with placebo. This rather complex crossover study consisted of four eight-week intervals of treatment in random order. The results in the sixty-seven people who completed the study showed that both forms of chromium significantly improved blood sugar control.
Positive results were also seen in three other double-blind, placebo-controlled studies enrolling more than 130 people with type 2 diabetes. However, several other studies have failed to find benefit for people with type 2 diabetes. These contradictory findings suggest that the benefit, if it really exists, is small at best.
A combination of chromium and biotin might be more effective.
Following positive results in a small pilot trial, researchers conducted a
double-blind study of 447 people with poorly controlled type 2 diabetes. One-half
the participants were given placebo, and the rest were given a combination of 600
mcg chromium (as chromium picolinate) with 2 mg of biotin daily. All participants
continued to receive standard oral medications for diabetes. In the ninety-day
study period, participants given the chromium-biotin combination showed
significantly better glucose regulation than those given placebo. The relative
benefit was clear in levels of fasting glucose and in HgA1c.
One placebo-controlled study of thirty women with pregnancy-related diabetes found that supplementation with chromium (at a dosage of 4 or 8 mcg chromium picolinate for each kilogram of body weight) significantly improved blood sugar control. Also, chromium has shown some promise for treating diabetes caused by corticosteroid treatment.
Improved blood sugar control in people without diabetes. Many
people develop impaired responsiveness to insulin (insulin
resistance) and mildly abnormal blood sugar levels. A few
small, double-blind trials have found that chromium supplementation may be
helpful, although two studies found no benefit. Another small, double-blind trial
found that chromium improved the body’s response to insulin among overweight
people at risk of developing diabetes. There is growing evidence that mildly
impaired blood sugar control increases the risk of heart disease, suggesting that
chromium supplementation might be useful.
Weight loss. The evidence is mixed on whether chromium is an effective aid for reducing weight or improving body composition (improving the ratio of fatty tissue to lean tissue). In one study, 219 people were given either placebo or 200 or 400 mcg of chromium picolinate daily. Participants were not advised to follow any particular diet. In seventy-two days, people taking chromium experienced significantly greater weight loss than those not taking chromium, more than two-and-one-half pounds versus about one-quarter pound. People taking chromium actually gained lean body mass, so the loss of fatty tissue was even more dramatic: more than four pounds versus less than one-half pound. However, a high dropout rate makes the results of this study somewhat unreliable.
However, in another double-blind study by the same researcher, 130 moderately overweight people attempting to lose weight were given either placebo or 400 mcg of chromium daily. At the end of the trial, no statistically significant differences in weight or body composition were seen between groups. Researchers were able to show benefit only by resorting to fairly complicated statistical maneuvers.
In a third study, forty-four overweight women were given either placebo or 400 mcg of chromium per day. All participants were placed on an exercise program. Through twelve weeks, no differences were seen between the two groups in terms of body weight, waist circumference, or percentage of body fat. A small double-blind trial of older women undergoing resistance training also failed to find evidence of benefit. Generally negative results also have been seen in other small double-blind trials.
When larger studies find positive results and smaller studies do not, it often indicates that the treatment under study is only weakly effective. This may be the case with chromium as a weight-loss treatment. If chromium is effective for weight loss, one small study suggests it may work by influencing the brain and its role in appetite and food cravings.
Heart disease prevention. Insulin resistance and mildly elevated blood sugar levels appear to increase the risk of heart disease. Chromium supplementation might help by improving insulin responsiveness and by normalizing blood sugar. In support of this, an observational trial found associations between higher chromium intake and reduced risk of heart attack.
Safety Issues
Although the precise upper limit of safe chromium intake is not known, it is believed that chromium is safe when taken at a dosage of 50 to 200 mcg daily. Side effects appear to be rare. However, chromium is a heavy metal and might conceivably build up and cause problems if taken to excess.
There is one report of kidney, liver, and bone marrow damage in a person who took 1,200 to 2,400 mcg of chromium for several months; in another report, as little as 600 mcg for six weeks was enough to cause damage. Such problems appear to be quite rare, and it is possible that these persons already had health problems that predisposed them to such a reaction. The risk of chromium toxicity is believed to be higher in people who already have liver or kidney disease.
Nonetheless, based on these reports, it is possible that the dosage of chromium found most effective for persons with type 2 diabetes (1,000 mcg daily) might present some health risks. For example, there is some evidence that if chromium is taken in high enough amounts, it may be converted from its original safe form (chromium 3) into a known carcinogen, chromium 6. One should consult a doctor before taking more than 200 mcg of chromium daily.
Persons who have diabetes and for whom chromium is effective may need to cut down the dosage of any medication taken for diabetes. Again, one should consult a doctor before continuing chromium use.
There are also several concerns about the picolinate form of chromium in particular. Picolinate can alter levels of neurotransmitters. This has led to concern among some experts that chromium picolinate might be harmful for persons with depression, bipolar disease, or schizophrenia. There also has been one report of a severe skin reaction caused by chromium picolinate.
Finally, there are fairly theoretical and uncertain concerns that chromium picolinate could have adverse effects on deoxyribonucleic acid (DNA). Also, the maximum safe dosage of chromium for women who are pregnant or nursing and for persons with severe liver or kidney disease has not been established.
Important Interactions
One may need extra chromium if also taking calcium carbonate supplements or
antacids. The chromium supplement and the doses of these
substances should not be taken within two hours of each other, because the two
together may interfere with chromium’s absorption.
People who are taking corticosteroids may need extra
chromium. Also, people who are taking oral diabetes medications or insulin should
seek medical supervision before taking chromium, because the dosages of these
drugs might need to be reduced. Finally, chromium supplementation may improve
levels of HDL (good) cholesterol if the individual is also taking
beta-blockers.
Bibliography
Albarracin, C. A., et al. “Chromium Picolinate and Biotin Combination Improves Glucose Metabolism in Treated, Uncontrolled Overweight to Obese Patients with Type 2 Diabetes.” Diabetes/Metabolism Research and Reviews 24 (2008): 41-51.
Anton, S. D., et al. “Effects of Chromium Picolinate on Food Intake and Satiety.” Diabetes Technology and Therapeutics 10 (2008): 405-412.
Diaz, M. L., et al. “Chromium Picolinate and Conjugated Linoleic Acid Do Not Synergistically Influence Diet- and Exercise-Induced Changes in Body Composition and Health Indexes in Overweight Women.” Journal of Nutritional Biochemistry 19 (2008): 61-68.
Docherty, J. P., et al. “A Double-Blind, Placebo-Controlled, Exploratory Trial of Chromium Picolinate in Atypical Depression: Effect on Carbohydrate Craving.” Journal of Psychiatric Practice 11 (2005): 302-314.
Lucidi, R. S., et al. “Effect of Chromium Supplementation on Insulin Resistance and Ovarian and Menstrual Cyclicity in Women with Polycystic Ovary Syndrome.” Fertility and Sterility 84 (2005): 1755-1757.
Pei, D., et al. “The Influence of Chromium Chloride-Containing Milk to Glycemic Control of Patients with Type 2 Diabetes Mellitus.” Metabolism 55 (2006): 923-927.
Yazaki, Y., et al. “A Pilot Study of Chromium Picolinate for Weight Loss.” Journal of Alternative and Complementary Medicine 16 (2010): 291-299.
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