From The February 1999 Issue of Nutrition Science News
By Stephanie Briggs, Ph.D.
Unless you're a bodybuilder, you're probably unaware of chromium supplements. Bodybuilders often take chromium picolinate in the belief that it diverts energy to building muscle and strength. Weight training itself, of course, achieves the same effect. Moreover, the majority of controlled studies in humans do not show a beneficial effect of chromium on body composition or strength in weight lifters.
The essentiality of chromium for human health, however, is without dispute. Chromium plays a role in the body's use of energy-providing carbohydrates, protein and fat and, when in short supply, is associated with impaired glucose tolerance and diabetes-like symptoms.  In 1977, the first published case of a chromium-diabetes link showed that the severe diabetic symptoms that developed in a woman while on long-term parenteral nutrition (intravenous feeding) were alleviated by supplemental chromium. [2 ]
This experience has been repeated many times since, and chromium is now routinely included in total parenteral nutrition formulas. Chromium causes insulin to function more effectively in the body, which in turn potentiates energy storage and regulates blood glucose. Insulin is an energy-storage hormone, and if not enough is produced, or if the insulin present is not sufficiently effective, the elevated blood glucose levels that normally follow a carbohydrate meal do not subsequently fall in the normal pattern. This occurs because glucose cannot enter the target cells in the liver, muscles and fat for storage or conversion to usable energy.
Chromium chloride, chromium picolinate and chromium polynicotinate are the most common supplemental sources available. Chromium picolinate absorption, while limited (less than 4 percent), is still significantly greater than that of chromium chloride.  The low absorption percentage, which decreases further when intake is increased, may be part of the reason chromium is not toxic.
In its trivalent form (in which three atoms can combine with other atoms), the only form found in supplements, chromium appears to be among the safest of nutrients. (Hexavalent chromiumhexa means sixis toxic, but it is not a nutrient, and it is not encountered in food.) The U.S. Food and Drug Administration has not evaluated chromium for daily intake values. The Environmental Protection Agency established a reference dosedefined as "an estimate of a daily exposure to humans, including sensitive subgroups, that is likely to be without an appreciable risk of deleterious side effects over a lifetime"that is 350 times the National Research Council's (NRC's) upper limit of the "safe and adequate" range.  Chromium chloride and chromium picolinate have been fed to rats at thousands of times the NRC's upper limit (on a body-weight basis) with no evidence of toxicity. [5 ]
|Nontoxic chromium picolinate supplements provide another means of controlling adult-onset diabetes.|
In Type I diabetesalso called juvenile- onset diabetesthe cells of the pancreas do not produce and secrete enough insulin. Type II diabetesalso known as adult-onset diabetes and non-insulin-dependent diabetesdevelops when the amount of insulin secreted is normal yet ineffective in causing cells to take in glucose from the blood. This condition, known as insulin resistance, is the first step in the development of Type II diabetes. A person may have insulin resistance but not necessarily an abnormally elevated blood-glucose level unless challenged with a glucose load such as that given in a glucose-tolerance test.
Chromium deficiency causes insulin resistance, and supplementation with adequate chromium overcomes that resistance. (There are, however, other causes of insulin resistance that are not chromium-based and thus not overcome by chromium supplementation.) In a four-month, double-blind study carried out in China, 180 people with Type II diabetes were given twice-daily doses of either placebo, 100 mcg chromium picolinate or 500 mcg chromium picolinate.  In measurements at two and four months, the group with the daily intake of 1,000 mcg chromium showed consistent improvement in biochemical indicators. They had significant reductions in blood-glucose and insulin concentrations two hours after a glucose load, fasting glucose and fasting insulin (measurements taken long after a meal, typically first thing in the morning), and glycosylated hemoglobin (a marker of long-term glucose control; lower is better). At 200 mcg per day, there was no improvement in fasting or two-hour glucose, but fasting and two-hour insulin decreased as much as with 1,000 mcg chromium picolinate per day. Glycosylated hemoglobin also fell, but less than with 1,000 mcg chromium picolinate daily. Thus, chromiumparticularly the higher dosagefavorably affected biochemical indicators of diabetes.
This and other such studies may pave the way for wider use of chromium for Type II diabetes, making the therapy more familiar and acceptable to physicians. The really important questionswhich remain to be answeredare whether the biochemical changes brought about by chromium supplementation reduce the complications of diabetes. It is likely that chromium's ability to reduce blood glucose will also reduce diabetic complications that stem from chronically elevated glucose.
It is generally presumed that chromium supplementation is of no benefit to people with Type I diabetes, since their problem is insulin insufficiency. Although this is the case, sometimes Type I is combined with Type II, and chromium supplementation helps the patient overall. For example, blood glucose and glycosylated hemoglobin concentrations fell in a 28-year-old woman with an 18-year history of Type I diabetes during a three-month period in which she took 200 mcg chromium picolinate twice daily.  Apparently, in addition to needing an outside source of insulin, she also had insulin resistance caused by chromium deficiency.
Chromium supplementation has also improved glucose tolerance and reduced hyperinsulinemia (abnormally elevated insulin levels in the blood) in women with gestational diabetes. 
Some diabetes studies have shown that chromium supplementation has a beneficial effect on plasma lipids, though study results have been far from uniform. In the Chinese study, total cholesterol was significantly reduced in the group receiving the higher dose of chromium.  In another study, 30 people with Type II diabetes took either 200 mcg chromium picolinate or placebo daily for two months and then, after a two-month "washout," took the other treatment for two months. The chromium treatment significantly lowered triglycerides, although the biochemical indicators of diabetes were unaffected.  Since heart disease is a typical complication of diabetes, reductions of serum lipids, made up largely of triglycerides, would be a welcome effect of chromium supplementation.
Body Composition Effects
|Obesity often accompanies Type II diabetes, but chromium may overcome insulin resistance and help diabetics lose weight.|
Another effect of chromium supplementation that could be a result of its potentiation of insulin sensitivity is the redistribution of body fat, protein and water. In a study of 154 volunteers, who were provided with no advice on weight loss, diet or exercise but were given a chromium picolinate supplement of 200 or 400 mcg per day for two months, the results were reductions in body fat percentage and indirect measurements of fat weight that were significantly greater than with placebo.  Notably, 400 mcg chromium was not better than 200. The average body-fat percentage of each group at the start of the study was 34 percentthat is, most of the volunteers were overweight.
Many of these people may have had insulin resistance to some degree. There is a positive correlation between obesity and insulin resistance (and Type II diabetes). Insulin, because it is a hormone that signals increased fat storage, decreases the ability to lose weight if present in higher than normal amounts. Thus, chromium may have overcome insulin resistance in these overweight subjects and thereby facilitated fat loss.
Not all studies have shown an effect of chromium on body composition, however. Combined with resistive training in young and older men, [11,12] chromium picolinate supplementation did not result in any more body-composition changes than did placebo. The experimental subjects may not have been chromium deficient or insulin resistant.
Unfortunately, there is no good measure of an individual's chromium status. Chromium can be measured in blood, but it is not a reliable indicator of chromium active in the tissues where it is needed. Levels of chromium present in hair may indicate long-term intake but does not reveal present status. Still, long-term statusthree monthsmay be a good general chromium indicator if diet and lifestyle do not change. In a healthy individual, chromium in urine is greatly affected by diet. Greater quantities of chromium are excreted when sugar consumption is high. This difficulty in satisfactorily measuring chromium levels presents a dilemma for physicians treating people with insulin resistance: They cannot diagnose chromium deficiency except by trying supplementation and watching the response.
Recently, a study in the United Kingdom measured chromium in the hair, sweat and serum of nearly 41,000 nonhospitalized people ranging in age from 1 to 75.  This was the first study to use reliable analytical methods in a large population. (Low-tech methodologies used before 1980 gave incorrectly high values. ) The investigators found that chromium levels declined with age in all three substances studied. Whether this represents normal physiologic development or poor nutrition is not known.
How Much Is Enough?
The Food and Nutrition Board of the NRC has recommended a "safe and adequate" range for dietary chromium of 50 to 200 mcg per day.  Food intake analyses suggest that, on average, Americans consume below the adequate level. For example, one analysis of 22 diets designed to be well balanced showed a range of daily intakes from 8.4 to 23.7 mcg per 1,000 calories (mean 13.4 mcg).  Does this suggest that most of our population is chromium deficient, or that the NRC's estimate of "adequate" is too high? Despite that mystery, we do know by chromium's effects on some symptoms of diabetes that insufficiency does occur in our population.
The best food sources of chromium appear to be broccoli, organ meats and processed meats. Plants do not require chromium, and the chromium content of food plants depends on the amount and form of chromium in the soil in which the plants grow. Thus, it is impossible to generate a reliable table of values from which to estimate a menu's chromium content.
There is much yet to be learned about chromium. While we wait for more information, however, people with Type II diabetes or those who know they are at risk for it might be well advised to try chromium supplementation. Be aware, however, that patients taking antidiabetic medications should try chromium supplementation with the cooperation of their doctor so glucose and insulin levels can be monitored. Medication dosages may need to be adjusted.
Stephanie Briggs, Ph.D., is a nutritional biochemist with more than 20 years' experience in laboratory research. She is also a freelance writer.
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