{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/41336"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/41336","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"The Effect of Whey Protein Isolate on Plasma Amino Acids, Nitrogen Balance, Glutathione and Performance during Energy Restriction in Athletes","abstract":"This study compared the effects of whey and casein on plasma AA, nitrogen balance (NBAL), glutathione and performance in dieting athletes. Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group.","abstract_html":"This study compared the effects of whey and casein on plasma AA, nitrogen balance (NBAL), glutathione and performance in dieting athletes. Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group.","abstract_has_math":false,"creators":["Heffron, Sean Patrick"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Human Nutrition, Foods, and Exercise","degree_department":"Human Nutrition, Foods, and Exercise","school":null,"contributors":[],"advisors":[],"committee_chairs":["Rankin, Janet L. Walberg"],"committee_members":["Webb, Kenneth E. Jr.","Nickols-Richardson, Sharon M."],"year":2004,"date_issued":"2004-02-23","date_published":"2004-02-23","updated_at":"2026-07-22T22:19:44Z","subjects":["cysteine","Immunocal","glutamine","casein"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03032004-215240"],"render_values":[{"text":"etd-03032004-215240","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/41336","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Rankin, Janet L. Walberg"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Webb, Kenneth E. 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Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["The Effect of Whey Protein Isolate on Plasma Amino Acids, Nitrogen Balance, Glutathione and Performance during Energy Restriction in Athletes"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Rankin, Janet L. Walberg"],"dc:contributor.committeemember":["Webb, Kenneth E. Jr.","Nickols-Richardson, Sharon M."],"dc:contributor.department":["Human Nutrition, Foods, and Exercise"],"dc:creator":["Heffron, Sean Patrick"],"dc:date.accessioned":["2014-03-14T21:30:30Z"],"dc:date.available":["2014-03-14T21:30:30Z","2005-03-15"],"dc:date.issued":["2004-02-23"],"dc:description.abstract":["This study compared the effects of whey and casein on plasma AA, nitrogen balance (NBAL), glutathione and performance in dieting athletes. Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-03032004-215240"],"dc:identifier.uri":["http://hdl.handle.net/10919/41336"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["cysteine","Immunocal","glutamine","casein"],"dc:title":["The Effect of Whey Protein Isolate on Plasma Amino Acids, Nitrogen Balance, Glutathione and Performance during Energy Restriction in Athletes"],"dc:type":["Thesis"],"thesis:degree_discipline":["Human Nutrition, Foods, and Exercise"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:44Z"}