Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable. It is found primarily in two forms: 1) trivalent (chromium 3+), which is biologically active and found in food, and 2) hexavalent (chromium 6+), a toxic form that results from industrial pollution. This fact sheet focuses exclusively on trivalent (3+) chromium
Trivalent chromium is found in a wide range of foods, including: whole-grain products, processed meats, high-bran breakfast cereals, coffee, nuts, green beans, broccoli, spices, and some brands of wine and beer. Most fruits and vegetables and dairy products only contain low amounts. Most of the chromium in people's diet comes from processing or storing food in pans and cans made of stainless steel, which can contain up to 18% chromium.
The amount of chromium in the body can be decreased as a result of a diet high in simple sugars, which increases the excretion of the metal through urine. Because of the high excretion rates and the very low absorption rates of most forms of chromium, acute toxicity is uncommon.
Approximately 2% of ingested chromium(III) is absorbed, with the remainder being excreted in the feces. Amino acids, vitamin C and niacin may enhance the uptake of chromium from the intestinal tract. After absorption, this metal accumulates in the liver, bone, and spleen.
Chromium deficiency is a disorder that results from an insufficient dietary intake of chromium. Whether or not such a deficiency ever occurs in people eating a normal diet is debated, and clear cases of deficiency have only been observed in hospital patients who were fed defined liquid diets intravenously for long periods of time. Although chromium is an essential trace element in humans, the basis for this need is not fully understood, since no chromium-containing biomolecules with beneficial effects have been characterized.
The symptoms of chromium deficiency caused by long-term total parenteral nutrition are severely impaired glucose tolerance, a loss of weight, and confusion. Another patient also developed nerve damage .
The body's chromium content may be reduced under several conditions. Diets high in simple sugars (comprising more than 35% of calories) can increase chromium excretion in the urine . Infection, acute exercise, pregnancy and lactation, and stressful states (such as physical trauma) increase chromium losses and can lead to deficiency, especially if chromium intakes are already low.
Type 2 diabetes and glucose intoleranceIn type 2 diabetes, the pancreas is usually producing enough insulin but, for unknown reasons, the body cannot use the insulin effectively. The disease typically occurs, in part, because the cells comprising muscle and other tissues become resistant to insulin's action, especially among the obese. Insulin permits the entry of glucose into most cells, where this sugar is used for energy, stored in the liver and muscles (as glycogen), and converted to fat when present in excess. Insulin resistance leads to higher than normal levels of glucose in the blood (hyperglycemia).
Chromium deficiency impairs the body's ability to use glucose to meet its energy needs and raises insulin requirements. It has therefore been suggested that chromium supplements might help to control type 2 diabetes or the glucose and insulin responses in persons at high risk of developing the disease. A review of randomized controlled clinical trials evaluated this hypothesis . This meta-analysis assessed the effects of chromium supplements on three markers of diabetes in the blood: glucose, insulin, and glycated hemoglobin (which provides a measure of long-term glucose levels; also known as hemoglobin A1C). It summarized data from 15 trials on 618 participants, of which 425 were in good health or had impaired glucose tolerance and 193 had type 2 diabetes. Chromium supplementation had no effect on glucose or insulin concentrations in the non-diabetic subjects nor did it reduce these levels in subjects with diabetes, except in one study. However, that study, conducted in China (in which 155 diabetics were given either 200 or 1,000 mcg/day of chromium or a placebo) might simply show the benefits of supplementation in a chromium-deficient population.
Trivalent chromium is found in a wide range of foods, including: whole-grain products, processed meats, high-bran breakfast cereals, coffee, nuts, green beans, broccoli, spices, and some brands of wine and beer. Most fruits and vegetables and dairy products only contain low amounts. Most of the chromium in people's diet comes from processing or storing food in pans and cans made of stainless steel, which can contain up to 18% chromium.
The amount of chromium in the body can be decreased as a result of a diet high in simple sugars, which increases the excretion of the metal through urine. Because of the high excretion rates and the very low absorption rates of most forms of chromium, acute toxicity is uncommon.
Approximately 2% of ingested chromium(III) is absorbed, with the remainder being excreted in the feces. Amino acids, vitamin C and niacin may enhance the uptake of chromium from the intestinal tract. After absorption, this metal accumulates in the liver, bone, and spleen.
Chromium deficiency is a disorder that results from an insufficient dietary intake of chromium. Whether or not such a deficiency ever occurs in people eating a normal diet is debated, and clear cases of deficiency have only been observed in hospital patients who were fed defined liquid diets intravenously for long periods of time. Although chromium is an essential trace element in humans, the basis for this need is not fully understood, since no chromium-containing biomolecules with beneficial effects have been characterized.
The symptoms of chromium deficiency caused by long-term total parenteral nutrition are severely impaired glucose tolerance, a loss of weight, and confusion. Another patient also developed nerve damage .
What affects chromium levels in the body?
Absorption of chromium from the intestinal tract is low, ranging from less than 0.4% to 2.5% of the amount consumed , and the remainder is excreted in the feces . Enhancing the mineral's absorption are vitamin C (found in fruits and vegetables and their juices) and the B vitamin niacin (found in meats, poultry, fish, and grain products) . Absorbed chromium is stored in the liver, spleen, soft tissue, and bone .The body's chromium content may be reduced under several conditions. Diets high in simple sugars (comprising more than 35% of calories) can increase chromium excretion in the urine . Infection, acute exercise, pregnancy and lactation, and stressful states (such as physical trauma) increase chromium losses and can lead to deficiency, especially if chromium intakes are already low.
When can a chromium deficiency occur?
In the 1960s, chromium was found to correct glucose intolerance and insulin resistance in deficient animals, two indicators that the body is failing to properly control blood-sugar levels and which are precursors of type 2 diabetes . However, reports of actual chromium deficiency in humans are rare. Three hospitalized patients who were fed intravenously showed signs of diabetes (including weight loss, neuropathy, and impaired glucose tolerance) until chromium was added to their feeding solution. The chromium, added at doses of 150 to 250 mcg/day for up to two weeks, corrected their diabetes symptoms . Chromium is now routinely added to intravenous solutions.Type 2 diabetes and glucose intoleranceIn type 2 diabetes, the pancreas is usually producing enough insulin but, for unknown reasons, the body cannot use the insulin effectively. The disease typically occurs, in part, because the cells comprising muscle and other tissues become resistant to insulin's action, especially among the obese. Insulin permits the entry of glucose into most cells, where this sugar is used for energy, stored in the liver and muscles (as glycogen), and converted to fat when present in excess. Insulin resistance leads to higher than normal levels of glucose in the blood (hyperglycemia).
Chromium deficiency impairs the body's ability to use glucose to meet its energy needs and raises insulin requirements. It has therefore been suggested that chromium supplements might help to control type 2 diabetes or the glucose and insulin responses in persons at high risk of developing the disease. A review of randomized controlled clinical trials evaluated this hypothesis . This meta-analysis assessed the effects of chromium supplements on three markers of diabetes in the blood: glucose, insulin, and glycated hemoglobin (which provides a measure of long-term glucose levels; also known as hemoglobin A1C). It summarized data from 15 trials on 618 participants, of which 425 were in good health or had impaired glucose tolerance and 193 had type 2 diabetes. Chromium supplementation had no effect on glucose or insulin concentrations in the non-diabetic subjects nor did it reduce these levels in subjects with diabetes, except in one study. However, that study, conducted in China (in which 155 diabetics were given either 200 or 1,000 mcg/day of chromium or a placebo) might simply show the benefits of supplementation in a chromium-deficient population.
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