|Classification and external resources|
Chromium deficiency is a proposed disorder that results from an insufficient dietary intake of chromium. It is an unlikely condition. Clear cases of deficiency have been observed only in hospital patients who were fed defined liquid diets intravenously for long periods of time.
The US dietary guidelines for adequate daily chromium intake were lowered in 2001 from 50–200 µg for an adult to 30–35 µg (adult male) and to 20–25 µg (adult female). These amounts were set to be the same as the average amounts consumed by healthy individuals. Consequently, it is thought that few Americans are chromium deficient.
Chromium may fall in the same category as manganese, where it is likely that many people get too much.
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.
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 contain only low amounts. Most of the chromium in people's diets 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.
Signs and symptoms
The symptoms of chromium deficiency caused by long-term total parenteral nutrition are severely impaired glucose tolerance, weight loss, and confusion. However, subsequent studies questioned the validity of these findings.
A natural form of chromium extracted from yeast, Glucose Tolerance Factor (GTF) chromium, was found to exert beneficial insulin-mimetic and insulin-potentiating effects in vitro and in a mouse model the GTF form was seen to produce an insulin-like effect by acting on cellular signals downstream of the insulin receptor. These beneficial results were seen to suggest Glucose Tolerance Factor as a potential source for a novel oral medication for diabetes.
However, recent studies in humans "have concluded that chromium supplements have no demonstrated effects on healthy individuals" and chromium picolinate in particular is described as a "poor choice" as a supplement. A meta-analysis in 2002 found no effect on blood glucose or insulin in healthy people, and the data were inconclusive for diabetics. Subsequent trials gave mixed results, with one finding no effect in people with impaired glucose tolerance, but another seeing a small improvement in glucose resistance. A 2007 review again concluded that chromium supplements had no beneficial effect on healthy people, but that there might be an improvement in glucose metabolism in diabetics, although the authors stated that the evidence for this effect remains weak.
Although it is controversial whether supplements should be taken by healthy adults eating a normal diet, chromium is needed as a component of the defined liquid diet that is given to patients receiving total parenteral nutrition (TPN), since deficiency can occur after many months of this highly restricted diet. As a result, chromium is added to normal TPN solutions, although the trace amounts found even in "chromium free" preparations may be enough to prevent deficiency in some individuals. Recent studies have challenged the methodology of earlier studies, concluding that chromium should not be regarded as an essential element.
Not all supplemental chromium is bioequivalent.
- Comparative studies of chromium(III) picolinate and niacin-bound chromium(III), two popular dietary supplements, reveal that chromium(III) picolinate produces significantly more oxidative stress and DNA damage. Studies have implicated the toxicity of chromium picolinate in renal impairment, skin blisters and pustules, anemia, hemolysis, tissue edema, liver dysfunction; neuronal cell injury, impaired cognitive, perceptual and motor activity; enhanced production of hydroxyl radicals, chromosomal aberration, depletion of antioxidant enzymes, and DNA damage. Recently, chromium picolinate has been shown to be mutagenic and picolinic acid moiety appears to be responsible as studies show that picolinic acid alone is clastogenic. Niacin-bound chromium(III) has been demonstrated to be more bioavailable and efficacious and no toxicity has been reported.
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- Chromium in glucose metabolism
- UC Berkeley[dead link]
- -66715645 at GPnotebook
- Diabetes Journal - Role of Chromium in Human Health and in Diabetes