Absorption of chromium

The bioavailability of chromium(III) was determined in 8 healthy adults who were administered 400 pg chromium(III)/day as chromium picolinate for 3 consecutive days by Gargas et al. (1994). The mean absorption of chromium was 2.8% 1.4 % (standard deviation). 

Urinary excretion data from 15 female and 27 male subjects given 200 pg chromium(III) as chromium trichloride indicated that gastrointestinal absorption was at least 0.4% (Anderson et al. 1983). Net absorption of chromium(III) by a group of 23 elderly subjects who received an average of 24.5 pg/day (0.00035 mg chromium(III)/kg/day) from their normal diets was calculated to be 0.6 pg chromium(III)/day, based on an excretion of 0.4 pg chromium/day in the urine and 23.9 pg chromium/ day in the feces, with a net retention of 0.2 pg/day. Thus about 2.4% was absorbed. The retention was considered adequate for their requirements (Bunker et al. 1984). 

The amount of absorption of chromium(VI) and chromium(III) was measured in four male and two female volunteers (ages ranging from 25 to 39 years) treated orally with potassium chromate (chromium(VI)) or chromic oxide (chromium(III)) in capsules at doses of 0.005 mg/kg/day and 1.0 mg/kg/day, respectively (Finley et al. 1996b). Subjects were exposed to each compound for 3 days. Based on urinary excretion data, mean absorption of potassium chromate was 3.4% (range 0.69-11.9%). No statistically significant increase in urinary chromium was observed during chromic oxide dosing,... 

Given the low absorption of chromium compounds by the oral route, the major pathway of excretion after oral exposure is through the feces. 

An age-related difference in the extent of gastrointestinal absorption of chromium(III) was reported in one study (Sullivan et al. 1984) it is not known if a similar relationship would exist for chromium(VI). No other information is available which evaluated potential differences between adults and children. Toxicokinetic studies examining how aging can influence the absorption, distribution, and excretion of chromium, particularly chromium(VI) would be useful in assessing children s susceptibility to chromium toxicity. There are no data to determine whether there are age-specific biomarkers of exposure or effects or any interactions with other chemicals that would be specific for children. There is very little available information on methods for reducing chromium toxic effects or body burdens it is likely that research in adults would also be applicable to children. 

The spectra have allowed us to verify the introduction of chromium in the composition of the catalytic materials. After impregnation (CrlOiN), the absorptions are measured at wavelengths that do not much differ from the absorption of chromium (III) chloride in octahedral coordination, characterized by two bands of ligand-metal charge transfer between 210 and 280 nm and two bands relative to the d-d transitions with absorptions between 450 and 630 nm. The thermal treatment (CrlOiT) has caused a widening of the second band (around 300 nm) attributable, from the data of the literature [19], to the... 

Anderson R and Bryden NA (1983) Concentration, insulin potentiation, and absorption of chromium in beer. J Agric Food Chem 31 308-311. 

The absorption of chromium is affected by the route of entry, its oxidation state, and the nature of its ligands. Elemental chromium from cooking and manufacturing processes involving stainless steel equipment is probably not absorbed and does not appear to have any nutritional value [8]. The most common ionic forms of chromium are and Cr however, under nutritional situations Cr is rapidly reduced to [9]. 

There are numerous reports of interactions of dietary elements that cause variation in the absorption of chromium. Amino acids, which chelate chromium, prevent precipitation at the basic pH in the small intestine, which increases its absorption [13]. Other chelating agents have mixed effects. Phytates significantly decrease absorption whereas oxalates lead to increased absorption [15]. Certain vitamins such as nicotinic acid and ascorbic acid have been shown to increase absorption [16]. Starch has also been shown to increase absorption to a greater degree than glucose, fructose, and sucrose. Some metals can compete with chromium and decrease its absorption. Studies show that zinc, vanadium, and iron have a common intestinal transport mechanism with chromium and can decrease the absorption of chromium [9]. 

Only very small amounts of chromium are required. The estimated safe and adequate adult daily dietary intake is 50-200//g/day (National Research Council 1989). Below intakes of about 40//g/day, fractional oral absorption of chromium increases as intake is decreased (Anderson and Kozlovsky 1985). Biologically active Cr(III) may be more efficiently absorbed from the gastrointestinal tract than other forms of soluble chromium (Mertz and Roginski 1971). 

Chelating agents—Other molecules that bind (chelate) mineral elements may alter the amounts of chromium which are absorbed and retained within the body. For example, oxalate (occurs in spinach and rhubarb) increases, while phytate (present in whole grains and legumes) decreases the absorption of chromium salts. However, the feeding of oxalate also causes a great increase of chromium in the urine. 

Fats—One way in which dietary fat may reduce the absorption of chromium is by stimulating the flow of bile, which is an alkaline secretion. Alkaline substances tie up inorganic chromium in soluble masses that cannot be absorbed. 

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