CROMIUM

_{TREATMENT OF CARDIOVASCULAR DISEASE AND DIABETES WITH CHROMIUM:}

Diabetes Mellitus is a condition characterized by a raised concentration of glucose in the blood because of a deficiency in the production and/or action of insulin, a pancreatic hormone made in special cells called the islet cells of Langerhans.
    

Chromium is an essential trace mineral required for normal protein, fat and carbohydrate metabolism. Chromium levels are known to decrease with age, and marginal deficiencies appear to be wide-spread. Insufficient dietary chromium has been linked to maturity-onset diabetes and cardiovascular disease. There is also evidence that chromium may play a role in lowering blood pressure, regulating appetite, reducing sugar cravings and promoting lean body mass. Chromium has been shown to reduce harmful LDL cholesterol by an average of 14%.

 

Chromium has a positive effect towards glucose metabolism, enhancing insulin action as well as seeming to have a positive effect in lipid metabolism and in the prevention of atherosclerosis. The RDA for adults ranges between 50-200 mcg.

Chromium

Chromium is a mineral that works with insulin in the metabolism of sugar and stabilization of blood sugar levels. Chromium also cleans the arteries by reducing cholesterol & triglyceride levels; helps transport amino acids to where the body needs them; and helps control the appetite.
 

Medical research has shown that persons with low levels of chromium in their bodies are more susceptible to having cancer and heart problems, and of becoming diabetic.
 

A deficiency of chromium may result in glucose intolerance in diabetics; atherosclerosis, heart disease, depressed growth, obesity, and/or tiredness.
 

A biologically active form of chromium participates in glucose metabolism by enhancing the effects of insulin. Insulin is secreted by specialized cells in the pancreas in response to increased blood glucose (sugar) levels, for example, after a meal. Insulin binds to insulin receptors on the surface of cells, activating those receptors and stimulating glucose uptake by cells. Through its interaction with insulin receptors, insulin provides cells with glucose for energy and prevents blood glucose levels from becoming elevated. In addition to its effects on carbohydrate (glucose) metabolism, insulin also influences the metabolism of fat and protein. A decreased response to insulin or decreased insulin sensitivity may result in impaired glucose tolerance or type II diabetes, also known as non-insulin dependent diabetes mellitus (NIDDM). Type II diabetes is characterized by elevated blood glucose levels and insulin resistance.

The precise structure of the biologically active form of chromium is not known. Recent research suggests that a low-molecular-weight chromium-binding substance (LMWCr) may enhance the response of the insulin receptor to insulin. The following is a proposed model for the effect of chromium on insulin action. 1)The inactive form of the insulin receptor (IR) is converted to the active form by binding insulin. 2) The binding of insulin by the IR stimulates the movement of chromium into the cell and results in binding of chromium to apoLMWCr, a form of the LMWCr that lacks chromium. 3) Once it binds chromium the LMWCr binds to the insulin receptor and enhances its activity. The ability of the LMWCr to activate the insulin receptor is dependent on its chromium content. 4) When insulin levels drop due to normalization of blood glucose levels, the LMWCr may be released from the cell in order to terminate its effects.

Nutrient interactions:

Iron: Chromium competes for one of the binding sites on the iron transport protein, transferrin. However, supplementation of older men with 925 mcg of chromium/day for 12 weeks did not significantly affect measures of iron nutritional status. A study of younger men found an insignificant decrease in transferrin saturation with iron after supplementation of 200 mcg of chromium/day for 8 weeks, but no long-term studies have addressed this issue (6). Iron overload in hereditary hemochromatosis may interfere with chromium transport by competing for transferrin binding. This has led to the hypothesis that decreased chromium transport might contribute to the diabetes associated with hereditary hemochromatosis.

Vitamin C: Chromium uptake is enhanced in animals when given at the same time as vitamin C (1). In a  study of three women, administration of 100 mg of vitamin C together with 1 mg of chromium resulted in higher plasma levels of chromium than 1 mg of chromium without vitamin C. 

Carbohydrates: Diets high in simple sugars (e.g., sucrose), compared to diets high in complex carbohydrates (e.g., whole grains), increase urinary chromium excretion in adults. This effect may be related to increased insulin secretion in response to the consumption of simple sugars compared to complex carbohydrates.

DEFICIENCY

Chromium deficiency was reported in three patients on long-term intravenous feeding who did not receive supplemental chromium in their intravenous solutions. These patients developed evidence of abnormal glucose utilization and increased insulin requirements that responded to chromium supplementation. Additionally, impaired glucose tolerance in malnourished infants responded to an oral dose of chromium chloride. Because chromium appears to enhance the action of insulin and chromium deficiency has resulted in impaired glucose tolerance, chromium insufficiency has been hypothesized to be a contributing factor to the development of Type II diabetes (see Disease Prevention and Disease Treatment). 

Several studies of male runners indicated that urinary chromium loss was increased by endurance exercise, suggesting that chromium needs may be greater in individuals who exercise regularly. In a more recent study, resistive exercise (weight lifting) was found to increase urinary excretion of chromium in older men. However, chromium absorption was also increased, leading to little or no net loss of chromium as a result of resistive exercise.

At present, research on the effects of inadequate chromium intake and risk factors for chromium insufficiency are limited by the lack of sensitive and accurate tests for determining chromium nutritional status.

The Adequate Intake Level (AI): Because there was not enough information on chromium requirements to set a recommended dietary allowance (RDA), the Food and Nutrition Board set an adequate intake level (AI) based on the chromium content in normal diets.

HEALTH CLAIMS

Increases muscle mass:  Claims that chromium supplementation increases lean body mass and decreases body fat are based on the relationship between chromium and insulin action (see Function). In addition to affecting glucose metabolism, insulin is known to affect fat and protein metabolism. At least 12 placebo-controlled studies have compared the effect of chromium supplementation (200-1,000 mcg as chromium picolinate/day) with or without an exercise program on lean body mass and measures of body fat. In general, those studies that have used the most sensitive and accurate methods of measuring body fat and lean mass (dual energy x-ray absorbtiometry or DEXA and hydrodensitometry or underwater weighing) do not indicate a beneficial effect of chromium supplementation on body composition.

Promotes weight loss: Controlled studies of chromium supplementation (200-400 mcg as chromium picolinate/day) have demonstrated little if any beneficial effect on weight loss, and claims of weight loss in humans appear to be exaggerated. In 1997 the U.S. Federal Trade Commission (FTC) ruled that there is no basis for claims that chromium picolinate promotes weight loss and fat loss in humans.

DISEASE PREVENTION

Impaired glucose tolerance and type II (non-insulin dependent) diabetes: In 12 out of 15 controlled studies of people with impaired glucose tolerance, chromium supplementation was found to improve some measure of glucose utilization or to have beneficial effects on blood lipid profiles. Impaired glucose tolerance refers to a metabolic state between normal glucose regulation and overt diabetes. Generally, blood glucose levels are higher than normal, but lower than those accepted as diagnostic for diabetes. Impaired glucose tolerance is associated with increased risk for cardiovascular diseases but is not associated with the other classic complications of diabetes. About 25% to 30% of individuals with impaired glucose tolerance eventually develop type II diabetes. Generally, chromium supplementation at doses of about 200 mcg/day, in a variety of forms (see Supplements) for two to three months were found to be beneficial. The reasons for the variation or lack of effect in some studies are not clear, but chromium depletion is not the only known cause of impaired glucose tolerance. Additionally, the lack of an accurate measure of chromium nutritional status prevents researchers from identifying those individuals who are most likely to benefit from chromium supplementation.

Cardiovascular diseases: Impaired glucose tolerance and type II diabetes are associated with adverse changes in lipid profiles and increased risk of cardiovascular diseases. Studies examining the effects of chromium supplementation on lipid profiles have been notable for their inconsistent results. While some studies have observed reductions in total cholesterol, LDL-cholesterol, and triglyceride levels or increases in HDL-cholesterol levels, others have observed no effect. Such inconsistent responses of lipid and lipoprotein levels to chromium supplementation may reflect differences in chromium nutritional status. It is possible that only those individuals with insufficient chromium will experience beneficial effects on lipid profiles due to chromium supplementation.

DISEASE TREATMENT

Type II (non-insulin dependent) diabetes: Type II diabetes is characterized by elevated blood glucose levels and insulin resistance. Although insulin levels in type II diabetics may be higher than in healthy individuals, the physiological effects of insulin are reduced. Because chromium is known to enhance the action of insulin, the relationship between chromium nutritional status and type II diabetes has generated considerable scientific interest. Individuals with type II diabetes have been found to have higher rates of urinary chromium loss than healthy individuals, especially those with diabetes of more than 2 years duration.  Prior to 1997, well-designed studies of chromium supplementation in individuals with type II diabetes showed no improvement in blood glucose control, though they provided some evidence of reduced insulin levels and improved blood lipid profiles. In 1997, the results of a large placebo-controlled trial conducted in China indicated that chromium supplementation may be beneficial in the treatment of type II diabetes.  One hundred eighty participants took either a placebo, 200 mcg/day, or 1,000 mcg/day of chromium in the form of chromium picolinate. At the end of four months, blood glucose levels were 15%-19% lower in those that took 1,000 mcg/day compared with those that took a placebo. Blood glucose levels in those that took 200 mcg/day did not differ significantly from those that took a placebo. Insulin levels were lower in those who took either 200 mcg/day or 1000 mcg/day. Glycosylated hemoglobin levels, a measure of long-term control of blood glucose, were also lower in both chromium supplemented groups, but they were lowest in the group taking 1,000 mcg/day. Because the chromium nutritional status of the Chinese participants was not evaluated, and the prevalence of obesity was much lower than is typically associated with type II diabetics in the U.S., extrapolation of these results to a U.S. population is difficult. However, the findings in the Chinese population emphasize the need for large-scale randomized controlled trials of chromium supplementation for type II diabetes in the U.S.

Gestational diabetes: Few studies have examined the effects of chromium supplementation on gestational diabetes. Gestational diabetes occurs in about 2% of pregnant women and usually appears in the second or third trimester of pregnancy. Blood glucose levels must be tightly controlled to prevent adverse effects on the developing fetus. After delivery, glucose tolerance generally reverts to normal. However, 30% to 40% of women who have had gestational diabetes develop type II diabetes within 5 to 10 years. Women with gestational diabetes whose diets were supplemented with 4 mcg of chromium per kilogram of body weight daily as chromium picolinate for 8 weeks had decreased fasting blood glucose and insulin levels compared with those who took a placebo. However, insulin therapy rather than chromium picolinate was required to normalize severely elevated blood glucose levels.

SOURCES

Food sources: The amount of chromium in foods is variable, and it has been measured accurately in relatively few foods. Presently, there is no large database for the chromium content of foods. Processed meats, whole grain products, ready-to-eat bran cereals, green beans, broccoli, and spices are relatively rich in chromium. Foods high in simple sugars, such as sucrose and fructose, are not only low in chromium but have been found to promote chromium loss. Estimated average chromium intakes in the U.S. range from 23-29 mcg/day for adult women and 39-54 mcg/day for adult me. The chromium content of some foods is listed in the table below in micrograms (mcg).

*Because chromium content in different batches of the same food has been found to vary significantly, the information in the table above should serve only as a guide to the chromium content of foods. 

Supplements: Chromium (III) is available as a supplement in several forms: chromium chloride, chromium nicotinate, chromium picolinate, and high-chromium yeast. They are available as stand-alone supplements or in combination products. Doses typically range from 50 to 200 mcg of elemental chromium. Chromium nicotinate and chromium picolinate may be more bioavailable than chromium chloride. In much of the research on impaired glucose tolerance and type II diabetes, chromium picolinate was the source of chromium.

THE LINUS PAULING INSTITUTE RECOMMENDATION

The lack of sensitive indicators of chromium nutritional status in humans makes it difficult to determine the level of chromium intake most likely to promote optimum health. Following the Linus Pauling Institute recommendation to take a multivitamin/multimineral supplement containing 100% of the daily values (DV) of most nutrients will generally provide 60-120 mcg/day of chromium, well above the adequate intake level of 20 to 25 mcg/day for adult women and 30 to 35 mcg for adult men (see The RDA).

Adults over the age of 65: Although the requirement for chromium is not known to be higher for older adults, one study found that chromium concentrations in hair, sweat, and urine decreased with age. Following the Linus Pauling Institute recommendation to take a multivitamin/multimineral supplement containing 100% of the daily values (DV) of most nutrients should provide sufficient chromium for most older adults.

                                     BACK TO PRESCRIPTIONS