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Latest Research On Chromium

7304-eat1Chromium is an essential trace mineral, which means it’s required for human nutrition but in small amounts. The notion that chromium is an essential mineral first surfaced with studies on rats conducted in the 1950s. Rats deprived of chromium became glucose intolerant.

Not long after the initial rat studies, other studies with humans who were on intravenous feeding also showed symptoms of glucose intolerance, along with weight loss and inflammation of peripheral nerves, in those who got no chromium. The symptoms reversed after chromium was added to the intravenous formula.

Brewer’s yeast, a popular supplement with bodybuilders in the ’50s and early ’60s, was thought to contain a “glucose tolerance factor” that enabled you to use carbohydrates more efficiently. Scientists conjectured that the GTF was a complex consisting of chromium, along with the B-vitamin niacin and a few amino acids. In fact, that was strictly a guess, since no one was ever able to determine its precise structure. What was known was that brewer’s yeast was rich in chromium. In fact, it’s one of the best natural sources. Other food sources include whole grains, and mushrooms, with tiny amounts found in coffee, tea and even red wine.

Chromium is thought to work by increasing the effectiveness of insulin. Among other functions, insulin ferries glucose into cells for use as an energy source. Insulin is also the most “fattening” hormone in the body, since it favors the production and storage of bodyfat from excess calories. In recent years science has revealed a lesser known function of insulin: It can provide anabolic effects in muscle. In reality, however, it’s more of an anticatabolic activity, in that it blunts muscle breakdown. On the other hand, insulin may provide some anabolic effects when accompanied by a high blood level of essential amino acids.

Precisely how chromium makes insulin more effective isn’t known. One theory suggests that it aids insulin in binding to cell receptors. Another suggests that it promotes the release of substances that aid insulin activity in the cell. A number of studies have examined whether chromium is useful for treating diabetics, who are known to excrete it more readily and are also insulin insensitive. They have had mixed results, with some showing beneficial effects, and others showing little or no effect.

One reason for that may be the fact that chromium is not well absorbed. Even sources such as chromium picolinate, which has a higher uptake rate, have an average absorption of less than 3 percent.  So getting a true therapeutic effect from chromium may require larger doses. While the suggested daily dose of chromium is 200 micrograms, studies showing beneficial effects have featured as much as 1,000 micrograms a day.

Chromium’s reputation regarding insulin  has made it popular with bodybuilders and those seeking fat loss. Since insulin has some anabolic effects, the idea is that chromium, by increasing insulin effectiveness, would give an anabolic boost. It was bolstered by a series of studies published in the late 1980s that featured high school football players given either chromium picolinate or a placebo. Those who got the chromium had increased muscle mass, strength and fat loss.

The problem is, the studies didn’t control for calorie intake, and it could be that the athletes who gained muscle simply ate more. In addition, the studies used calipers to check body composition, a technique that is considered inexact and crude. Later studies that used more sophisticated body comp methods and sought to replicate those initial favorable studies saw no changes in muscle mass, strength or body composition in those who used chromium supplements.

Since insulin in the presence of excess calories favors bodyfat storage, chromium was also touted as a “fat-loss supplement.” Here again, the notion was that if chromium did indeed make insulin work better, the body would have less need to secrete larger amounts of insulin, thus producing less bodyfat synthesis. It sounded good on paper, but once again, when put to the test in well-controlled studies, chromium proved no more effective than a placebo in promoting fat loss.

Then there was the controversy about toxicity. One study, which involved exposing isolated hamster ovary cells to a large concentration of chromium picolinate, found damage to DNA, which is required for efficient cellular replication. Such damage is considered a mutagenic process, which means there’s a possibility of tumor formation. The study was criticized because of its isolated-cell design. No actual cells in a human body would ever be exposed to the amount of chromium used in the study because chromium is poorly absorbed. On the other hand, it’s also known that chromium is stored in the body in various compartments, with some retaining it far longer than others. How that affects health isn’t known.

A couple of other scattered case studies have shown some possible toxic effects of taking chromium. One involved a woman who took 1,200 to 2,400 micrograms of chromium a day for five months in an effort to lose bodyfat. She developed kidney failure. Another woman took 600 micrograms of chromium a day for six weeks and also developed kidney failure. A 24-year-old bodybuilder developed rhabdomyolysis, or rapid muscle breakdown, after taking 1,200 micrograms of chromium picolinate. Even so, none of the individual case histories ever linked the medical problems directly to chromium.

Some forms of chromium are without question not only toxic but also carcinogenic, meaning cancer causing; for example, the industrial form of chromium used on car bumpers. That form is called hexavalent chromium, while the type found in food and supplements is trivalent chromium. A famous case years ago involved contamination of a local water supply with hexavalent chromium, which resulted in an increased cancer rate. The toxic water supply was exposed by Erin Brockovich, and the case was the subject of a movie in which Brockovich was portrayed by Julia Roberts, who won an Academy Award for the role. Trivalent chromium is considered safe.

More recently, an alarming study was published about chromium that has special significance for bodybuilders and others who use the supplements.1 Chromium is not only sold as a stand-alone supplement but is also often included in various mineral, vitamin-and-mineral, meal-replacement and even protein supplements. As a result, a bodybuilder who uses those supplements every day can ingest a hefty dose of chromium without even realizing it. Considering chromium’s low absorption rate, you would think that it wouldn’t be a problem—or would it?

The new study was designed to test whether chromium supplements actually do boost insulin sensitivity, since the evidence is conflicting. The study featured a double-blind, placebo-controlled, randomized design, considered the gold standard among science studies. The subjects consisted of 31 nonobese people, aged 20 to 50, who showed no signs of either a chromium deficiency or insulin resistance, such as persistent elevated resting blood glucose. They used no medications that would affect their blood glucose. They were given either a placebo or 500 micrograms of chromium picolinate, twice daily.

After a few weeks the subjects switched, with those who got the chromium now getting the placebo, and vice versa. As mentioned, it was a double-blind study, meaning that neither the scientists nor the subjects knew which was the real chromium until the end of the 16-week experiment.

The results showed no difference in insulin sensitivity with the chromium or the placebo, but there was an unexpected and shocking finding: Those with the most chromium in their bodies showed a deterioration of glucose sensitivity. That, of course, was precisely the opposite of what would be expected with a chromium supplement. Since no one was obese or had high blood glucose at the start of the study, those factors could not have affected the results. Urinary chromium measures indicated that the subjects had been compliant, and the technique used to measure insulin action was the most accurate available. Measurements of gene activity also failed to find any abnormality that would explain the paradoxical drop in glucose sensitivity in those with the highest retention of chromium. So the researchers concluded that chromium not only doesn’t increase insulin sensitivity in the nonobese but in large doses may actually increase insulin insensitivity.

Several questions come to mind about this study. For one, since the subjects weren’t obese and had no indications of a prior chromium deficiency, would the same results occur in obese people, who are prone to excess insulin release due to lack of insulin sensitivity? What about those who have a chromium deficiency? Surely the negative results would not apply to them either. And diabetics, who already have problems with insulin, often lack sufficient chromium, so this research may not apply to them.

As for bodybuilders, perhaps those who are not carrying excess bodyfat need to be more conscious of their chromium intake, but of the 31 subjects in the study, only four showed an insulin insensitivity effect after using chromium. That could be an idiosyncratic reaction that doesn’t affect everyone, only those who for some reason absorb more chromium.

Finally, whenever you take in rapidly absorbed carb sources, you lose chromium. For that reason alone I’d suggest that most bodybuilders and other active people who consume carbohydrates don’t have to worry too much about getting too much chromium. —Jerry Brainum


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1 Masharini, U., et al. (2012). Chromium supplementation in non-obese, non-diabetic subjects is associated with a decline in insulin sensitivity. BMC Endocrine Disorders.12:31.


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