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Carter wins APS Partnership for Clean Competition New Investigator Award

February 19, 2015

Stephen J. Carter, PhD, ACSM-CPT, postdoctoral fellow in the Nutrition Obesity Research Center (NORC) and Department of Human Studies, recently received the Partnership for Clean Competition New Investigator Award through the Environmental and Exercise Physiology section of the American Physiological Society (APS) for recent work titled, "Race Differences in Erythropoietin, 25-hydroxyvitamin D, and Hemoglobin Before and After Weight Loss in Women." The honor recognizes “outstanding research in either environmental, exercise, or thermal physiology by a postdoctoral fellow involving the impact of training/environmental stress on hematological profiles and is designated by the Steering Committee as an outstanding example of experimental research." As recipient of this award, Dr. Carter will be attending APS’ Experimental Biology Meeting, held March 28 to April 1, 2015, in Boston.

Energy restriction is known to affect erythropoietic-activity, at least in part, through changes in serum 25-hydroxyvitamin D [25(OH)D] and testosterone. Since, African American (AA) women commonly exhibit lower hemoglobin compared with European American (EA) women and low hemoglobin is an independent predictor of cardiovascular disease, it was of interest to clarify the potential for race-specific adverse effects of weight loss on hemoglobin. In the study, sixty-four overweight (BMI, 27-29.9 kg/m2) premenopausal women were furnished with an 800 kcal/day diet for the purpose of losing weight. Ancestry informative markers were used to provide estimates of African genetic admixture, an objective and linear mean of expressing race. Anthropometric and blood sampling were completed at baseline and again upon meeting goal BMI (<25 kg/m2) following a 2-week weight stabilization period.

At baseline, hemoglobin (g/dL) (AA, 11.6 +/- 0.9 vs. EA, 12.5 +/- 0.8; P < 0.01) and serum 25(OH)D (ng/mL) (AA, 14.2 +/-  5.4 vs. EA, 19.6 +/- 5.9; P < 0.01) were lower while erythropoietin (mIU/mL) was higher (AA, 14.3 +/- 9.8 vs. EA, 7.9 +/- 2.4; P < 0.01) in AA women compared with EA women. Following weight loss, hemoglobin was significantly decreased in both races (AA, 11.2 +/- 1.1 vs. EA, 12.1 +/- 0.9; P < 0.01), although the magnitude of change was not different among races. Additionally, 25(OH)D (AA, 17.4 +/-5.6 vs. EA, 27.3 +/- 9.7; P < 0.01) and erythropoietin (AA, 24.2 +/- 24.7 vs. EA, 8.6 +/- 4.9, P < 0.01) were increased in both races. After adjusting for African genetic admixture, changes in testosterone and body fat percent, the effects of weight loss on hemoglobin were positively associated with changes in 25(OH)D (r = 0.386; P < 0.01).

The investigation demonstrated that significant calorie restriction to achieve weight loss lowers hemoglobin, independent of African genetic admixture. Similar to others, the study showed that fat mass reduction increases serum 25(OH)D. Importantly though, participants who demonstrated the largest increase in 25(OH)D also exhibited the smallest decrease in hemoglobin, thus supporting the role of 25(OH)D in erythrocyte-regulation. Further research is needed to clarify if slightly less severe calorie restriction and/or vitamin D supplementation can protect hemoglobin during weight loss, although it should be noted that a limitation of this study is that only total 25(OH)D values were available, and as such, further studies are needed to examine the association between hemoglobin and the bioavailable fraction of 25(OH)D with weight loss.

Co-authors of the abstract and manuscript (a portion of this work is currently in-review at the European Journal of Applied Physiology) are Dr. Carter’s mentor Professor Gary R. Hunter, PhD; Assistant Professor Eric P. Plaisance, PhD; and Assistant Professor Gordon Fisher, PhD, in the Department of Human Studies; as well as Professor and Vice Chair for Education José Fernández, PhD, and Professor Barbara A. Gower, PhD, in the Department of Nutrition Sciences.