The element chromium is what makes emeralds green and rubies red, and according to some people, it’s what puts the beef in muscle. Chromium is an essential trace mineral whose main function appears to be a tight interaction with the hormone insulin. Insulin has gone from being known as a medication for diabetics to allegedly being one of the most potent anabolic substances produced in the body. While it’s easy to promote an increased insulin secretion with diet, some athletes inject themselves with insulin because they believe it has an anabolic effect in muscle when combined with other drugs, such as anabolic steroids and growth hormone.
The recognition that chromium somehow makes insulin work better first surfaced in animal studies, where a deprivation of chromium led to insulin insensitivity and elevated blood fat levels. Later those same effects showed up in hospital patients who were being tube-fed. If their nutritional formula didn’t include chromium, they, too, showed symptoms of a failure to use insulin properly.
Much of the confusion about chromium is due to the various forms it appears in. The two primary forms are trivalent and hexavalent. Trivalent chromium is required in human nutrition and is also found in food and supplement sources. Hexavalent is industrial chromium’what you’d find on a car bumper, for example’and it’s not suitable for human consumption, despite the fact that it’s absorbed far easier into cells than the nutritional form. Hexavalent chromium, or chromium-6, is a carcinogen, and it recently achieved a higher level of notoriety as the poison found in a community water supply that’s the subject of the film Erin Brockovich.
Since the trivalent form of chromium is known to potentiate insulin activity, and since insulin is without doubt an anabolic hormone, the idea that chromium may offer significant anabolic effects through its close partnership with insulin appears to make sense. But what does the research show?
Chromium Research
The initial study that led to increased focus on chromium as a potential anabolic mineral was published by Gary Evans, Ph.D., a former United States Department of Agriculture mineral researcher who later became a professor at Bemidji State University in Minnesota.1 In Evans’ study, which involved football players who took 200 micrograms of chromium picolinate a day for six weeks, the athletes lost 7 1/2 pounds of fat while gaining six pounds of lean mass. While that sounds impressive, Evans was criticized by many other researchers because of what some considered poor methodology, such as using skinfold techniques to determine the athletes’ body composition changes.
In a follow-up study involving beginning weight-training students of both sexes, all the subjects showed gains in size, but there was no difference between the gains of those who got chromium picolinate and those who got a placebo.2 Only the women subjects gained significant body mass, yet they showed no changes in body composition, leading many to wonder exactly what they gained.
Seeking to replicate Evans’ initial positive findings, another researcher designed a study that also involved football players who got a 200-microgram dose of chromium.3 The results, however, showed no changes in measures of strength or body composition, although the subjects taking the chromium excreted five times the chromium that those who got the placebo excreted.
In a more recent study 15 female softball players took either 500 micrograms of chromium picolinate or a placebo for six weeks while also engaged in a regular weight-training program.4 The researchers found no significant differences in muscular strength or body composition between the chromium group and those getting the placebo.
Another recent study featured 44 women, aged 27 to 51, who were randomly assigned to receive a placebo or 400 micrograms of chromium a day.5 The women also participated in a weight-training and walking program two days a week for 12 weeks. There were no significant differences in body composition, resting metabolic rate, plasma glucose, serum insulin, glucagon or blood lipid levels between those taking the chromium and those taking the placebo. Nor were there changes in the levels of other minerals, such as zinc or iron.
So it appears that, based on the majority of existing research, chromium doesn’t have any significant beneficial effects on fat loss or muscular growth. In fact, in one study, again involving women, those taking 400 micrograms of chromium picolinate for nine weeks who didn’t exercise showed gains in bodyfat.6
Getting Enough
Despite those findings, it’s also true that it’s difficult to get sufficient chromium from food alone. The suggested healthy range for chromium intake is 50 to 200 micrograms daily, yet studies show that most women in the United States get an average of 25 micrograms, while men get 33 micrograms. Even worse, in a study that used a computerized model to design a perfectly balanced diet, the amount of chromium in the so-called perfect diet was a modest 33 micrograms’less than the minimum suggested daily intake.
This discrepancy may be related to two factors. The first is that it’s difficult for the body to absorb chromium from food sources. Most texts say that you can only absorb 0.4 to 2 percent from food sources, such as whole grains, green beans, broccoli and spices. Even the highly touted chromium picolinate form is absorbed at a rate of only about 2.8 percent.7 Another problem is that certain substances either help or hinder chromium absorption. Amino acids increase chromium uptake, while phytate, a substance existing in vegetables and whole grains, interferes with it. Other helpers include oxalate, found in vegetables; vitamin C and the B-complex vitamin niacin. Zinc interferes with chromium uptake, and absorption increases during a zinc deficiency.
Brewer’s yeast is a rich natural source of chromium. Some experts suggest that in yeast, chromium exists as part of the glucose tolerance factor (GTF), the form in which it is most active. No one has ever precisely charted the makeup of the GTF, but besides chromium it also consists of the amino acids glycine, cysteine and glutamic acid, as well as niacin. While the scientists are still debating whether GTF is the most potent form of chromium complex, when chromium is found in yeast, the body’s uptake of it goes up to 25 percent, far greater than with other food or supplement sources.
Chromium and Insulin
Whatever else is true, recent studies have confirmed that chromium does indeed potentiate insulin activity in the body. It does that by being incorporated into a complex composed of six amino acids in a specific sequence that’s known as low-molecular-weight chromium-binding substance (LMWcr) and that appears to boost insulin activity in cells.
Another ongoing controversy surrounds the question of which is the best supplemental form of chromium. In supplemental form chromium is bound to either picolinate or polynicotinate, the latter being a niacin complex. A rarely used third form, chromium chloride, is inorganic and is used more in research studies than in food supplements. Picolinate is a derivative of the essential amino acid L-tryptophan and was initially discovered by the same scientist who provided the first ‘anabolic’ chromium picolinate study, Gary Evans.
One study showed that the chromium polynicotinate had a 311 percent greater absorption rate when directly compared to chromium picolinate.8 But the most serious charge against the picolinate form is that it may promote cancer, similar to what happens with industrial chromium. That assertion is based on a study in which Chinese hamster egg cells were exposed to a dose of chromium about 3,000 times greater than the suggested oral dose and showed mutagenic, or cancer-inducing, changes. Animal studies involving living creatures showed no toxic effects even when the animals received huge doses.9 That likely relates to chromium’s low absorption rate. Out of 209 experiments with chromium involving megadoses, mutagenic effects showed up in only 48, which is not considered a significant figure.10
Chromium picolinate is absorbed differently from other forms of chromium. One scientist has suggested that in the presence of vitamin C, chromium picolinate metabolism may lead to the release of hydroxyl radicals, a dangerous form of free radicals, or unstable electrons, known to cause cellular damage.11 In addition, it may interfere with the function of brain chemicals, such as serotonin, dopamine and norepinephrine. Some experts suggest that picolinate also interferes with the activities of other minerals in the body, including zinc.
Some isolated human side effects linked to chromium picolinate have appeared in the published literature. In one case a woman was diagnosed with interstitial nephritis, a kidney inflammation, which occurred five months after she took a six-week course of chromium picolinate’600 micrograms daily. Another case involved a woman who showed liver dysfunction and kidney failure after using 1,200 to 2,400 micrograms of chromium picolinate daily for five months. A 24-year-old female bodybuilder developed rhabdomyolysis (excess muscle breakdown) after taking 1,200 micrograms of chromium picolinate. Other cases involve single instances of skin inflammations in men who used chromium picolinate supplements.
Note that the people involved all took large doses for extended periods. Yet in a recent study of diabetics in China subjects getting 1,000 micrograms of chromium a day had no side effects. Perhaps the people involved in the toxicity studies described above also were using other substances that led to their medical problems. Scientists who’ve studied mineral metabolism agree that chromium has a lower order of toxicity than other minerals, such as zinc, iron and copper.
Speaking of iron, some studies, but not all, show that chromium can interfere with the body’s iron metabolism. That relates to the fact that both chromium and iron are transported in the blood attached to a protein called transferrin. The notion here is that chromium may displace iron in transferrin, leading to iron excretion. If anything, however, that may be beneficial, since men don’t need to take supplemental iron, and excess free iron has been linked to cardiovascular disease and cancer.
Chromium appears to offer considerable benefits to diabetics and people who have a genetic predisposition to diabetes. Some studies show that if you have hypoglycemia, or low blood sugar, chromium will normalize the blood glucose level. The same is true if you have elevated blood glucose, as occurs in uncontrolled diabetes and prediabetics. If your blood glucose level is normal, chromium does nothing.
A series of recent studies shows other benefits linked to chromium. For example, two studies presented at the 2001 meeting of the American Diabetes Association confirmed that chromium improves insulin sensitivity and normalizes the function of a protein that promotes glucose absorption into muscle (GLUT-4). The other study showed that chromium improved the transport of glucose into muscle that’s often inhibited by fat intake.
Research shows that you lose chromium every time you secrete insulin, an effect that’s greatly heightened after you eat any type of simple, or high-glycemic-index, sugar. You also excrete chromium after intense exercise.
So what’s the bottom line about chromium? If you show any signs of blood glucose problems, such as being prediabetic or having low blood sugar, chromium supplements will likely help you. If you eat large amounts of simple sugars, you’ll lose chromium too. Ditto if you’re using insulin injections. But the truth is that chromium is so ubiquitous in food supplements these days, you’d have to go out of your way to induce an actual chromium deficiency. Even so, keep in mind that food sources of chromium are poorly absorbed, and if you favor a high-carb diet and aren’t using any supplements containing chromium, it would be prudent to take about 200 micrograms a day in supplemental form.
References
1 Evans, G.W. (1989). The effect of chromium picolinate on insulin-controlled parameters in humans. Int Biosoc Med Res. 11:163-180.
2 Hasten, D.L., et al. (1992). Effect of chromium picolinate on beginning weight-training students. Int J Sports Nutr. 2:343-50.
3 Clancy, S.P., et al. (1994). Effects of chromium picolinate supplementation on body composition, strength and urinary chromium loss in football players. Int J Sports Nutr. 4:142-153.
4 Livolsi, J.M., et al. (2001). The effect of chromium picolinate on muscular strength and body composition in women athletes. J Strength Cond Res. 15:161-66.
5 Volpe, S.L., et al. (2001). Effect of chromium supplementation and exercise on body composition, resting metabolic rate, and selected biochemical parameters in moderately obese women following an exercise program. J Am Coll Nutr. 20:293-296.
6 Grant, K.E., et al. (1997). Chromium and exercise training: effect on obese women. Med Sci Sports Med. 29:992-998.
7 Lim, T.H., et al. (1983). Kinetics of trace element chromium-3 in the human body. Am J Physiol. 244:R445-54.
8 Olin, K.L., et al. (1994). Comparative retention/absorption of chromium chloride, chromium polynicotinate and chromium picolinate in a rat model. Trace Elem Electrolytes. 11:182-186.
9 Anderson, R.A., et al. (1997). Lack of toxicity of chromium chloride and picolinate in rats. J Am Coll Nutr. 16:273-279.
10 Jeejeebhoy, K.N. (1999). The role of chromium in nutrition and therapeutics and as a possible toxin. Nutrition Reviews. 57:329-35.
11 Vincent, J.B. (2000). The biochemistry of chromium. J Nutr. 130:715-718. IM
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