Solid-State Structural Studies of Chromium(III) Nicotinato Nutritional Supplements

Evaluation of Chromium and Manganese levels in sports supplements using graphite furnace atomic absorption spectrometry

ABSTRACT Objective In this paper, we studied three different types of ordinary sports supplements containing whey protein: whey protein-based ones, hypercaloric ones, and protein bars. Methods A sample preparation procedure was studied employing microwave-assisted wet digestion in order to determine the Chromium and Manganese levels by graphite furnace atomic absorption spectrometry. Results The developed methods have presented good accuracy (recoveries in the range of 90% to 109%) and precision (Relative standard deviation <8%). Although an adequate detectability was obtained (50ng g-1 for Manganese and 65ng g-1 for Chromium), the sample preparation method was also adequate to inductively coupled plasma mass spectrometry analysis. The method was applied to 26 commercial samples, in which the Chromium concentrations were in the range between 0.22 and 1.0μg g-1 and the Manganese concentrations varied from 2.0 to 37μg g-1. Conclusion The results obtained by atomic absorption for both analytes were in agreement with those obtained by mass spectrometry. In addition, some samples presented concentrations of Chromium above the recommended daily intake and, as a result, we used the X-ray powder diffraction technique as an analytical tool to evaluate the oxidation state of Chromium in such samples.

The Identity of "Chromium Malate"

Recently, several studies on the effects of a compound named "chromium malate," with the proposed formula "Cr₂malate₃·xH₂O" where x = 3.5 or 5, on the health of healthy and diabetic rats have appeared. However, the compound is poorly characterized, and knowing the identity of this material could be important in the interpretation of the previous and of future studies on the effects of this compound in animals. Consequently, the synthesis, characterization, and identity of this material were explored. A combination of spectroscopic, magnetic, and elemental analyses and mass spectral studies reveal that the compound is probably a polymer, not a discrete molecule, and does not have the composition previously reported. The repeating unit of the polymer possesses an antiferromagnetically coupled trinuclear Cr(III) core. The current study suggests that previous reports on chromium malate and its effects in animals must be viewed with caution.

New Evidence against Chromium as an Essential Trace Element

Nearly 60 y ago, chromium, as the trivalent ion, was proposed to be an essential element, but the results of new studies indicate that chromium currently can only be considered pharmacologically active and not an essential element. Regardless, articles still continue to appear in the literature claiming chromium is an essential element. Chromium has been marketed as an agent to reduce body mass and develop muscle; however, such marketing claims are no longer allowed in the United States because these claims, similar to claims of essential status, are not supported by experiments. Trivalent chromium has also been proposed as a therapeutic agent to increase insulin sensitivity and affect lipid metabolism. Although effective in certain rodent models, beneficial effects in humans have not been unequivocally established. Molecular mechanisms have been proposed for the beneficial effects but have not been definitively shown to occur in animals.