The trace mineralchromium is considered a star nutrient for bodybuilders and other athletes. Past studies have shown that chromium potentiates the role of insulin in the body. Insulin, a hormone produced in the beta cells of the pancreas, is involved in several anabolic
actions and works in concert with other anabolic hormones, such as testosterone and growth hormone. As the power of insulin is upgraded, so are it's anabolic effects. No one knows precisely how chromium works, but one popular theory holds that the mineral allows insulin
to bind more tightly to cellular receptors. This, in turn, makes the cellular cascade of biochemical events (induced by insulin) work at a more efficient pace.
Another hypothesis is that chromium interacts with insulin inside the cell itself. For bodybuilders, the benefits of chromium relate mostly to the increased insulin efficiency: By making insulin more efficient, chromium may aid bodyfat loss. Insulin promotes bodyfat accretion (increase) when too many calories, in relation to activity levels, are consumed. On the other hand, consuming excess calories and taking supplemental chromium may promote bodyfat synthesis (loss) through increased insulin action. Now, here are the controversies about chromium: Early studies on the mineral indicated that it increased muscle; however, most of those studies featured poor controls (including the methods used to assess body composition and a lack of monitoring for other substances, such as anabolic steroids, known to have anabolic effects) and thus were not considered scientifically sound.
Later studies among athletic populations taking chromium often failed to detect either increases in muscle or decreases in bodyfat. Researchers also argue over which form of chromium is best. Chromium chloride, a type rarely found in food supplements, is used in many studies. The two most popular supplemental forms of the mineral, however, are chromium picolinate and chromium polynicotinate. Proponents on all sides are vociferous, frequently declaring superiority of one form over the others based on "scientific evidence." Hoping to determine which form of chromium is best, scientists from Missouri and Louisiana recently tested all three on groups of rats (Nutrition Research, 17:283-94, 1997). The 12-week study showed that all three forms of chromium were equally effective in lowering bodyfat in one group of rodents. The fat loss was associated with an enhanced rate of insulin-induced thermogenesis (the production of heat in the body). None of the animals showed an increase in lean body mass. The authors suggested that this may have been due to the fact that the animals were not deficient in chromium. Jt might also be that chromium works better for muscle building under certain conditions that weren't evident in this study, such as supplementing during intense exercise (noted for increasing chromium loss from the body) or while consuming a high- carbohydrate diet (which also promotes chromium excretion).
The reports of toxicity associated with supplemental chromium intake are more problematic. As noted in a previous edition of this column, most of the alarming reports concerning toxicity have turned out to be red herrings. For example, chromium picolinate added to a test tube containing hamster cells induced pathological changes. However, the amount of chromium used was about 6,000 times the suggested human dose. A subsequent study failed to find any evidence of adverse effects from chromium picolinate, even at levels 10,000 times the human dosage. While the type of chromium found on car bumpers (hexavalent) is indeed carcinogenic, no evidence exists that the type found in food and supplements (trivalent) has any cancer- causing effects. You'd know all too well if you had consumed poisonous hexavalent chromiurn poisonous by the resulting symptoms- including nausea, vomiting, ulcers, circulatory shock and hepatitis. Workers exposed to industrial hexavalent chromium have 15 times the normal incidence of lung cancer and often experience kidney damage through accumulation of the metal in their renal filtering structures.
A few reports, aside from the hamster-cell study, do suggest potential problems with chromium picolinate. One says that picolinic acid (a metabolite of the amino acid tryptophan in a complex with chromium picolinate) is associated with altered salivary-gland activity. Another report says it alters normal cell shape. Still another warns of an interference with iron metabolism, setting the stage for anemia in susceptible persons. In a downright scary letter recently published in the Annals of Internal Medicine (126:410, 1997), two physicians describe a 49-year-old female nurse who suffered from kidney failure after taking large doses of chromium picolinate for five months. For the six weeks before she was admitted to a hospital, this woman had ingested 600 micrograms a day of chromium picolinate. The physicians writing up the case noted that the woman "ingested chromium picolinate at levels 12-45 times the usual intake of dietary chromium, and three times the recommended dose for dietary supplementation." The precise diagnosis was severe active interstitial nephritis. which is often linked to exposure to toxic heavy metals (not rock bands, but stuff like arsenic, lead and cadmium). This side effect, however, as noted earlier, is more often associated with hexavalent (industrial grade) chromium, not the trivalent type found in food and supplements.
While a case like this is alarming at first glance, on closer perusal, it may have little if any relevance for most bodybuilders. For one thing, recent studies of diabetics in China show that 1,000 mcg of chromium picolinate daily had no adverse effects on those subjects. Mother consideration is that the Internal Medicine letter deals with just one case study. Proving a connection between chromium intake and kidney failure would require other case studies with similar outcomes. The nurse's predicament may simply represent an anomaly in the way her body disposes of high doses of chromium picolinate. Also, that report did not discuss whether the woman had used any other drugs, though the article did state that she had showed normal kidney function two years earlier.
Finally, we must consider the absorption rate of chromium. Some studies show that the maximum level of absorption of dietary chromium is only about 3% of the ingested dose. Both exercise and consumption of carbohydrates speed the egress of chromium from the body. Thus, it appears that it would be nearly impossible for most active people to store enough chromium in their bodies to cause toxicity. In fact, the primary problem is getting too little of the mineral rather than too much. Some studies (see Advanced Nutrition, July 1997) have shown that 200 mcg are sufficient, but bodybuilders should measure their chromium intake against their carb intake, since carbs can cause the body to rapidly excrete chromium.