Absorption of chromium from the intestinal tract is low, ranging from less than 0.4% to 2.5% of the amount consumed, with 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.

As already mentioned, 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.

There are reports of significant age-related decreases in the chromium concentrations of hair, sweat and blood, which might suggest that older people are more vulnerable to chromium depletion than younger adults. One cannot be sure, however, as chromium status is difficult to determine. That's because blood, urine, and hair levels do not necessarily reflect body stores. Furthermore, no chromium-specific enzyme or other biochemical marker has been found to reliably assess a person's chromium status.

There is considerable interest in the possibility that supplemental chromium may help to treat impaired glucose tolerance and type 2 diabetes, but the research to date is inconclusive. No large, randomized, controlled clinical trials testing this hypothesis have been reported. Nevertheless, this is an active area of research.

Chromium has also long been of interest for its possible connection to various health conditions. Among the most active areas of chromium research are its use in supplement form to treat diabetes, lower blood lipid levels, promote weight loss, and improve body composition.

In 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.

Overall, the value of chromium supplements for diabetics is inconclusive and controversial. Randomized controlled clinical trials in well-defined, at-risk populations where dietary intakes are known are necessary to determine the effects of chromium on markers of diabetes.

The effects of chromium supplementation on blood lipid levels in humans are also inconclusive. In some studies, 150 to 1,000 mcg/day has decreased total and low-density-lipoprotein (LDL or "bad") cholesterol and triglyceride levels and increased concentrations of apolipoprotein A (a component of high-density-lipoprotein cholesterol known as HDL or "good" cholesterol) in subjects with atherosclerosis or elevated cholesterol or among those taking a beta-blocker drug. These findings are consistent with the results of earlier studies.

However, chromium supplements have shown no favorable effects on blood lipids in other studies. The mixed research findings may be due to difficulties in determining the chromium status of subjects at the start of the trials and the researchers' failure to control for dietary factors that influence blood lipid levels.

Chromium supplements are sometimes claimed to reduce body fat and increase lean (muscle) mass. Yet a recent review of 24 studies that examined the effects of 200 to 1,000 mcg/day of chromium (in the form of chromium picolinate) on body mass or composition found no significant benefits. Another recent review of randomized, controlled clinical trials did find supplements of chromium picolinate to help with weight loss when compared to placebos, but the differences were small and of debatable clinical relevance. In several studies, chromium's effects on body weight and composition may be called into question because the researchers failed to adequately control for the participants' food intakes. Furthermore, most studies included only a small number of subjects and were of short duration.

Few serious adverse effects have been linked to high intakes of chromium, so the Institute of Medicine has not established a Tolerable Upper Intake Level (UL) for this mineral. Certain medications may interact with chromium, especially when taken on a regular basis and therefore you should consult your doctor before proceeding with supplementation.

Chromium is a widely used supplement. Estimated sales to consumers were $85 million in 2002, representing 5.6% of the total mineral-supplement market. Chromium is sold as a single-ingredient supplement as well as in combination formulas, particularly those marketed for weight loss and performance enhancement. Supplement doses typically range from 50 to 200 mcg.

Chromium supplements are available as chromium chloride, chromium nicotinate, chromium picolinate, high-chromium yeast, and chromium citrate. Chromium chloride in particular appears to have poor bioavailability. However, given the limited data on chromium absorption in humans, it is not clear which forms are best to take.

Eating a variety of whole grains, fruits, vegetables, meats, and milk and milk products should provide sufficient chromium. According to Dietary Guidelines, "Nutrient needs should be met primarily through consuming foods. Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet."

The general dietary guidelines describes a healthy diet as one that emphasizes a variety of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products and includes lean meats, poultry, fish, beans, eggs, and nuts and is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars and stays within your daily calorie needs. (Reference: http://ods.od.nih.gov/factsheets/chromium.asp)