Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Kinesiology

First Advisor

B. Don Franks

Abstract

Several human and animal studies of chromium (Cr) supplementation in the form of Cr picolinate (CrPic) have reported increases in lean body mass, often with concurrent body fat decreases. This 12-week study examined the effects of six dietary levels of CrPic (0, 75, 150, 300, 600, 1500 ppb Cr) upon the growth and body composition of the rat. Ninety male Harlan Sprague-Dawley outbred weanling rats arrived in three groups of 30 animals (referred to as Blocks 1, 2, and 3). Five animals from each block were assigned to each treatment, resulting in a 6 x 3 (treatment x block) Randomized Block Design. Body composition was assessed via dual emission X-ray absorptiometry (DEXA). Significant treatment X block interactions were found for fat weight (p = 0.01 and 0.06 at Weeks 5 and 10), percent body fat (p = 0.02 and 0.09 at Weeks 5 and 10), and body weight (p = 0.07 and 0.04 at Weeks 10 and 12). These interactions reflected decreases in body fat for Block 1 that corresponded with increasing CrPic levels. No treatment interactions or effects were seen for growth rate, lean body mass, or tissue weights, but most block effects were highly significant (p = 0.01), with Block 2 $>$ Block 3 $>$ Block 1. These significant block effects were further reflected in the glucose tolerance data, in which Block 1 had lower resting glucose levels than Block 2 (p = 0.07) and lower glycated hemoglobin levels than both Blocks 2 and 3 (p = 0.09). A significant treatment x block interaction (p = 0.01) for feed intake revealed a decrease for Blocks 1 and 2, but an increase for Block 3, at the highest CrPic level. However, only Block 1 experienced corresponding changes in body composition. Furthermore, except for the highest CrPic level, body fat reductions for Block 1 occurred without decreases in feed intake, implicating possible dietary-induced thermogenic effects of CrPic. Genetic differences could have accounted for some of the differential effects of CrPic supplementation upon the blocks of animals. Additionally, more stringent Cr-free conditions may be necessary for changes in growth rate to occur, and exercise may be an important stimulus for potentiating increases in lean body mass.

Pages

188

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