Document Type

Thesis - University Access Only

Award Date

2005

Degree Name

Master of Science (MS)

Department / School

Consumer Sciences

Abstract

Protein intake influences serum IGF-I concentrations however, it is unknown whether the effects on human circulating IGF-I concentrations vary by high quality protein source such as beef, pork, and poultry. It is also unknown whether the effects of hi^ quality protein on lean body mass differ by protein source specifically beef, pork, and poultry. This study examines the effect of protein intake and protein source on lean body mass and circulating IGF-I concentrations. Covariates include age, sex, weight, height, mean kcal, protein intake, and percent time in moderate and vigorous activity. Data from 117 participants of the South Dakota Rural Bone Health Study (SDRBH) who had a fasted blood sample, had completed a protein food frequency questionnaire, and had completed at least three 24-hour diet and activity recalls within a one-year period were included in the current analysis. Body composition was measured by dual energy x-ray absorptiometry (DXA Hologic QDR4500A, software version 11.2). Concentrations of serum IGF-I were measured by radioimmunoassay. Women who had been pregnant within the previous six months, who were currently lactating, or had weaned a child within the past twelve months were excluded. GH and IGF-I play important roles in body composition. Growth hormone promotes protein anabolism and in response to its secretion IGF-Iis secreted from the liver and other tissues and enhances the transport of amino acids and glucose into the cells. Dietary protein intake and the quality of protein have a known effect on circulating IGF-I concentrations. Some research suggests supplementation with bovine colostrum may increase lean body mass due to IGF-I being absorbed intact. Some studies have found lean body mass increases with intake of animal proteins vs. plant proteins however, we are unaware of any studies which have examined the effects of beef, pork, and poultry on body composition. We found that females in the high beef consumption group had a significantly greater amount of lean body mass (g/kg) than females in the low beef consumption group before covariates were included in the model. Males in the high pork consumption group had a significantly greater amount of lean body mass (g/kg) than males in the low pork group. When total lean mass (kg) was analyzed, males in the low beef group had a greater amount of lean body mass than males in the high beef group (67 + 7vs. 65 + 5p=0.02, respectively). Our study did not find lean body mass (g/kg) to be associated with protein intake expressed as g/d, low or adequate, or g/kg in males or females when covariates were included in the model. Total body lean mass (kg) was not associated with protein intake expressed as g/d or low or adequate in males or females however, lean body mass was positively associated with protein intake expressed as g/kg among females (p=0.01), but not males (p=0.94). We did find serum IGF-I concentrations to be associated with protein intake expressed asg/kg in females (p=0.03), but not males (p=0.98) when covariates were included in the model. Serum IGF-I concentrations were not associated with protein intake expressed as g/d in females (p=0.l 1) or males (p=0.56) when covariates were included in the model. IGF-I concentrations were associated with total body lean mass (kg) in females (p=0.02), not males (p=0.86) when covariates were included in the model. In conclusion, we could speculate that our results may have been different if a stronger correlation existed between our protein questionnaire and diet recall. It is unclear why we observed a difference in lean body mass (g/kg) between females in the high beef vs. the low beef group when there were no significant differences in age, protein intake, weight, height, mean energy intake, or percent time in moderate and vigorous activity. It is also unknown why a significant difference in lean body mass (g/kg) existed among high vs. low pork males when there were no significant differences in age, protein intake, height, mean energy intake, or percent time in moderate and vigorous activity. Due to the preliminary nature of this study, further research is needed regarding the effect of specific protein sources on IGF-I and lean body mass.

Library of Congress Subject Headings

Proteins in human nutrition.
Somatomedin.
Human body -- Composition.

Format

application/pdf

Number of Pages

69

Publisher

South Dakota State University

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