Stability and absorption of chromium and absorption of chromium histidinate complexes by humans

Increased intake of chromium (Cr) often leads to improvements in glucose, insulin, lipids, and related variables in studies involving humans and experimental and farm animals. However, the results are often variable, depending not only on the selection of subjects but also dietary conditions and the form of supplemental Cr used. Our objective was to find a Cr supplement suitable for humans that was absorbed better than any of those available. Chromium absorption by six adult subjects, three males and three females, was determined based on the amount of Cr excreted in the urine in the initial 2 d following intake of 200 microg of Cr of the various forms of chromium tested. The absorption of the newly synthesized complexes was greatest for those containing histidine. Urinary Cr losses for six control subjects consuming 200 microg of Cr as Cr histidinate increased from basal levels of 256+/-48 to 3670+/-338 ng/d compared with 2082+/-201 ng for Cr picolinate, the currently most popular nutrient supplement, in the 48 h following Cr consumption. Chromium histidinate complexes were stable and absorption was similar to the initial values after more than 2 yr. Mixing of some of the complexes with starch, which was postulated to improve Cr absorption, was shown to essentially block Cr absorption within 1 mo. These data demonstrate that urinary Cr losses need to be determined because stability and absorption of the Cr complexes varies widely and could be responsible for the variability in some of the Cr supplementation studies. Chromium histidinate complexes are absorbed better than any of the Cr complexes currently available and need to be evaluated as Cr nutritional supplements.