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 out of 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, thus 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, as well, but other studies failed to find this effect.
The official US recommendations for daily intake are as follows:
- 0-6 months: 0.2 mcg
- 7-12 months: 5.5 mcg
- 1-3 years: 11 mcg
- 4-8 years: 15 mcg
- 9-13 years: 25 mcg
- 14-50 years: 35 mcg
- 50 years and older: 30 mcg
- 9-13 years: 21 mcg
- 14-18 years: 24 mcg
- 19-50 years: 25 mcg
- 50 years and older: 20 mcg
- Pregnant Women
- 18 years or younger: 29 mcg
- 19 years and older: 30 mcg
- Nursing Women
- 18 years or younger: 44 mcg
- 19 years and older: 45 mcg
Some evidence suggests that chromium deficiency may be relatively common. ^ However, this has not been proven, and the matter is greatly complicated by the fact that we lack a good test to identify chromium deficiency. ^ Severe chromium deficiency has only been seen in hospitalized individuals 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 4 ounces of calf liver supply between 50 mcg and 60 mcg of chromium. Other good sources of chromium are whole grains, beer, and cheese.
Calcium carbonate interferes with the absorption of chromium. ^
The dosage of chromium used in studies ranges from 200 mcg to 1,000 mcg daily, mostly in the form of chromium picolinate. However, there may be potential risks in the higher dosages of chromium (see Safety Issues ).
Note:These and all other dosages of chromium regard 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, since GTF is no longer believed to exist, this claim should be disregarded.
What Is the Scientific Evidence for Chromium?
The evidence regarding use of chromium for type 2 (adult onset) diabetes , as well as 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 2 months in the group receiving 1,000 mcg and in both chromium groups after 4 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 78 individuals with type 2 diabetes compared two forms of chromium (brewer's yeast and chromium chloride) against placebo. ^ This rather complex crossover study consisted of four 8-week intervals of treatment in random order. The results in the 67 participants 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 a total of 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. ^ Half the participants were given placebo and the rest were given a combination of 600 mcg chromium (as chromium picolinate) along with 2 mg of biotin daily. All participants continued to receive standard oral medications for diabetes. Over the 90 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 as well as in HgA1c.
One placebo-controlled study of 30 women with pregnancy -related diabetes found that supplementation with chromium (at a dosage of 4 mcg or 8 mcg chromium picolinate for each kilogram of body weight) significantly improved blood sugar control. ^ Chromium has shown a bit of 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. (See the section below on Heart Disease Prevention .)
#Weight Loss ("Fat Burning")
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 mcg or 400 mcg of chromium picolinate daily. ^ Participants were not advised to follow any particular diet. Over a period of 72 days, people taking chromium experienced significantly greater weight loss than those not taking chromium, more than 2-½ pounds versus about ¼ pound. Interestingly, people taking chromium actually gained lean body mass, so the loss of fatty tissue was even more dramatic: more than 4 pounds versus less than ½ pound. However, a very 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, 44 overweight women were given either placebo or 400 mcg of chromium per day. ^ All participants were placed on an exercise program. Over a period of 12 weeks, no differences were seen between the two groups in terms of body weight, waist circumference, or percentage body fat. A small double-blind trial of older women undergoing resistance training also failed to find evidence of benefit. ^ Generally negative results have been seen in other small double-blind trials as well. ^ 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, as well as mildly elevated blood sugar levels, appears to increase risk of heart disease . ^ ^ ^ ^ ^ ^ ^ Chromium supplementation might help by improving insulin responsiveness and normalizing blood sugar.
In support of this, an observational trial found associations between higher chromium intake and reduced risk of heart attack. ^