Chemistry Reference
In-Depth Information
10.16.
Chromium
Trivalent chromium was described as the glucose tolerance factor that
alleviated impaired glucose tolerance in rats fed torula yeast-sucrose diets
by Schwarz and Mertz (1959). Shortly thereafter, the glucose tolerance
factor, or GTF, evolved into a speculated organic form of chromium. In
1977, it was reported that chromium supplementation overcame what was
considered to be signs of chromium deficiency in a patient receiving total
parenteral nutrition (Jeejeebhoy et al., 1977). This report occurred during
the time when a mineral element often was accepted as essential based
simply on evidence that dietary deprivation consistently induced a change
in a biological function that was preventable or reversible by physiological
amounts of the element. As a result, chromium was widely regarded as
essential with a role in glucose metabolism. Thus, an estimated safe and
adequate daily dietary intake was established for chromium by the US Food
and Nutrition Board in 1980 (National Research Council, 1980). However,
doubts about the nutritional essentiality of chromium arose after it was
found that chromium analyses before 1980 were not valid and repeated
efforts to characterize definitively a chromium-containing GTF were not
successful. Additionally, studies on chromium essentiality subsequent to
1985 were not successful in showing that chromium deprivation consistently
impaired a biological function that was prevented by physiological or
nutritional amounts of chromium. Furthermore, early studies of chromium
essentiality provided supplements to controls that resulted in chromium
intakesover100timesthatofnormalnutritional intakes. Thus, the early
reports of chromium essentiality may have been describing pharmacologic
or supranutritional actions of chromium.
Although chromium apparently is losing its designation as an estab-
lished essential nutrient, there is much evidence showing that chromium is a
bioactive and beneficial element for higher animals and humans. Numerous
studies show that chromium beneficially affects circulating glucose, insulin
and lipids in humans and a variety of animal species (Stoecker, 2006). A study
that has received much attention found that 1000 mg chromium per day as
chromium picolinate for 4 months markedly reduced blood glucose and
glycated hemoglobin in diabetic Chinese subjects (Anderson et al., 1997b).
The basis for this finding may be chromodulin, a naturally occurring oligo-
peptide composed of glycine, cysteine, aspartate and glutamate that tightly
binds four chromium ions (Vincent and Bennett, 2007). Chromodulin appar-
ently amplifies the tyrosine kinase activity of insulin-activated insulin recep-
tor; the amplification is directly dependent upon the chromium content of
chromodulin (Vincent and Bennett, 2007).
