The safety and efficacy of high-dose chromium - High-Dose Chromium

Alternative Medicine Review, June, 2002 by Davis W. Lamson, Steven M. Plaza

The interaction of iron and chromium is thought to be linked to the shared binding sites on transferrin. Sargent et a1 (92) first proposed the theory that increased iron stores due to hemochromatosis might result in the competitive inhibition of chromium binding, leading to diabetic symptoms. He found that patients with hemochromatosis did, in fact, have significantly less plasma chromium than iron-depleted patients. Chromium has been found to preferentially bind to the B site of transferrin. When saturation of transferrin with iron increases in hemochromatosis to over 50 percent, iron competes with chromium binding, affecting its transport. (92) This theory is further supported by studies of patients with hemochromatosis who were found to have significantly higher excretion of the unbound plasma chromium as well as a smaller blood pool of chromium due to the saturation of transferrin by irony. (93)

It has been found that substances forming chelates with chromium generally stimulate absorption and that EDTA (ethylenediaminetetracetic acid) or DL-penicillamine significantly increase absorption as measured by [sup.51]Cr levels. (91) However Chen et a1 (94) found no significant difference in absorption when EDTA and [sup.51]Cr were administered to rats. Naturally occurring chelating agents, such as phytates and oxalates, have also been found to influence chromium absorption in both in vitro and in vivo rat studies. Rats fed chromium with oxalate were found to have higher [sup.51]Cr blood and tissue levels, while rats fed phytates with chromium had lower blood and tissue levels.

A number of amino acids have also been found to increase absorption of chromium from the intestine. It was found that a mixture of 20 amino acids nearly doubled the rate of absorption. Amino acids like histidine and glutamic acid that readily form complexes with chromium were also shown to increase absorption. (91)

Earlier studies found trivalent chromium had consistent absorption and excretion regardless of previous diet history (unlike the absorption of other elements). (4) In 1996 it was discovered that chromium analyses in biological samples prior to 1980 were inaccurate due to the state of early analytical instrumentation. (95) More recent, post-1980 studies, using more accurate instrumentation, now find dietary absorption to be inversely proportional to dietary chromium intake (as with other minerals). Humans consuming a self-selected diet with an intake of 10 mcg/day Cr III bad an absorption of two percent, while an intake of 40 mcg/day provided absorption of only 0.5 percent. (96)

Different forms of trivalent chromium have distinct characteristics of absorption, with inorganic complexes of trace minerals known to have lower levels compared to organic complexes. Chromite ores, chromic oxide, and chromium III chloride have historically been shown to have the lowest levels of absorption. Ingestion of inorganic salts such as chromium III chloride have levels of absorption ranging between 0.4-1.3 percent, with a mean of 0.69 percent. (82,83,97)