Chromium is an essential trace element for humans. Chromium in tissue is highest during infancy and decreases steadily with age. The average adult body contains about 600 mcg of chromium. Absorption occurs primarily in the jejunum and is affected by interactions with other metals, such as zinc, iron, and vanadium, and chelating agents, such as oxalate and phytate. After absorption, transferrin binds trivalent chromium and transports it to body tissues. Absorbed chromium is excreted primarily in the urine, with small amounts lost in hair, perspiration, and bile. Unabsorbed chromium (>99%) is lost in the feces.

Chromium must be converted to a biologically active form for physiological function. Glucose tolerance factor (GTF), a biologically active form isolated from brewer's yeast, contains chromium (III), nicotinic acid, and the amino acids glycine, glutamic acid, and cysteine. GTF potentiates insulin's actions and therefore influences carbohydrate, lipid, and protein metabolism. It works with insulin to facilitate glucose uptake, regulate blood sugar levels, and stimulate protein synthesis. The exact nature of the chromium-insulin interaction is unknown. Chromium may potentiate insulin action through direct action on insulin or its receptor, or it may regulate the synthesis of a molecule that potentiates insulin action. In clinical studies, GTF chromium has been shown to potentiate the effects of insulin and decrease serum cholesterol and triglycerides.

It is estimated that as many as 90% of all American diets are low in chromium. Individuals often consume less than the suggested minimum intake for chromium. The trend toward consuming highly processed foods may be a major contributing factor to this problem; appreciable losses of chromium occur in the refining of foods. Children with protein-calorie malnutrition, diabetics, and older individuals may be especially susceptible to chromium deficiency. Stressors such as elevated simple sugars, strenuous physical exercise or work, infection, and physical trauma may increase the loss of chromium, thereby increasing the need for chromium. Symptoms of chromium deficiency include glucose intolerance, elevated circulating insulin, glycosuria, fasting hyperglycemia, impaired growth, decreased longevity, elevated serum cholesterol and triglycerides, increased incidence of aortic plaques, peripheral neuropathy, brain disorders, decreased fertility and sperm count, negative nitrogen balance, and decreased respiratory quotient.

• Brewer's yeast (best dietary source when grown on chromium-rich medium)
• Lean meats (especially processed meats)
• Cheeses
• Pork kidney
• Whole-grain breads and cereals
• Molasses
• Spices
• Some bran cereals

Vegetables, fruits, and most refined and processed foods (except for some processed meats, which contain high amounts of chromium) contain low amounts of chromium. Hard tap water can supply 1% to 70% of one's daily intake. Cooking in stainless steel cookware increases the chromium content of food.

Chromium is a white, hard, brittle metal that occurs in any oxidation state from –2 to +6. Trivalent chromium is the most stable and biologically active oxidation state and forms compounds with other organic compounds.

Chromium is available commercially in several forms, including chromium polynicotinate, chromium picolinate, chromium-enriched yeast, and chromium chloride. Chromium is available in multivitamins and alone in tablet and capsule forms. Daily preparation doses are typically between 15 and 200 mcg chromium in multivitamins.

Diabetes. Chromium supplementation may improve glucose tolerance in healthy individuals and Type II diabetics with low chromium levels, and older individuals with abnormal glucose tolerance. Not all healthy individuals show a response to chromium supplementation. Individuals with low chromium levels appear to benefit the most from supplementation.

Poor dietary intake of chromium results in impaired glucose tolerance and symptoms similar to those of Type II diabetes mellitus. Individuals with marginally elevated blood glucose concentrations may benefit from chromium supplementation. One study assessed the effects of chromium supplementation (200 mcg chromium chloride per day) on 20 normal subjects with marginally impaired glucose tolerance. By the end of the three-month trial, 18 of the 20 subjects exhibited significant improvement in glucose tolerance.

Supplementation with chromium has also been shown to improve glucose tolerance in some diabetic patients. There is some indication that Type II diabetics may have an increased requirement for chromium. In one study, diabetic patients with severe complications, such as retinopathy and nephropathy, showed lower blood concentrations of chromium.

Older individuals are more susceptible to low tissue chromium levels, abnormal glucose tolerance, and increased incidence of diabetes and cardiovascular disease. Several studies have examined the correlation between low chromium levels and impaired glucose tolerance. In one clinical study, chromium supplementation improved glucose tolerance in 50% of older subjects (over age 70). Older individuals with mild abnormalities in glucose metabolism appear to benefit more from supplementation than those with extreme diabetic-like abnormalities in glucose intolerance.

Chromium is also used to treat the following conditions:

• Hypoglycemia. Chromium deficiency may be an underlying contributing factor of hypoglycemia in some individuals. Supplementation with 200 mcg of chromium improves the symptoms of hypoglycemia in some individuals.
• Cardiovascular disease. A low amount of chromium in the diet is associated with increased blood cholesterol and increased risk of developing cardiovascular disease. Supplementation with chromium has been shown to increase HDL cholesterol and lower triglyceride and total cholesterol levels in diabetics and in individuals with impaired glucose tolerance.
• Glaucoma. Chromium affects insulin receptors in the eye. There is a strong association between chromium deficiency and increased risk of glaucoma.
• Obesity. Preliminary evidence suggests that chromium supplementation may help reduce body fat and increase lean body mass in some individuals. Chromium's ability to increase insulin sensitivity may explain these effects.
• Osteoporosis. Chromium picolinate has been shown to decrease urinary excretion of calcium and hydroxy-proline in women, and may help preserve bone density in postmenopausal women.

There are no RDAs established for chromium. The estimated safe and adequate daily dietary intakes of chromium are as follows:

• Infants birth to 6 months: 10 to 40 mcg
• Infants 6 to 12 months: 20 to 60 mcg
• Children 1 to 3 years: 20 to 80 mcg
• Children 4 to 6 years: 30 to 120 mcg
• Children 7 to 10 years: 50 to 200 mcg
• 11+ years: 50 to 200 mcg

Dosage for disease prevention and treatment is typically 200 mcg chromium one to three times a day.

Excess intake or tissue accumulation of chromium can inhibit the effectiveness of insulin.

Hexavalent chromium is more toxic than trivalent. Industrial exposure to high amounts of chromium, usually airborne, can result in toxicity symptoms, including allergic dermatitis, skin ulcers, and bronchogenic carcinoma. Trivalent chromium, the form found in foods, is poorly absorbed; thus, extremely high amounts are necessary to attain toxic levels. Gastric irritation can occur at extremely high doses.

A total of 115 patients with either Type I or Type II diabetes who were treated with chromium (200 mcg/day) required lower doses of insulin, sulfonylurea drugs, and metformin (Ravina and Slezack 1993). The glycemic response to chromium treatment was greater for patients with Type II diabetes (57.2%). Chromium picolinate may benefit patients with Type II diabetes by increasing insulin sensitivity and stimulating insulin receptor sites (McCarty 1998).

Administration of 1 mL antacid suspension of calcium carbonate (150 mg) prior to treatment with 20 uCi ⁵¹chromium chloride minimized accumulation of chromium in the kidneys, testes, and spleen in male rats (Seaborn and Stoecker 1990). These findings are supported by another study with female rats given antacid (40 mg) by gastric intubation (0.5 mL) followed orally by 55 uCi ⁵¹chromium chloride; chromium absorption was hindered by pretreatment with antacid (Davis et al. 1995).

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