Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations

1-1-2006

Vitamin B-6 status of middle aged women consuming soymilk versus cow's milk

Yana Chen Iowa State University

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Recommended Citation Chen, Yana, "Vitamin B-6 status of middle aged women consuming soymilk versus cow's milk" (2006). Retrospective Theses and Dissertations. 19380. https://lib.dr.iastate.edu/rtd/19380

This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Vitamin B-6 status of middle aged women consuming soymilk versus cow's milk

by

Yana Chen

A thesis submitted to the graduate faculty

in partial fulfillment of the requirements for the degree of

MASTED OF SCIENCE

Major:

Program of Study Committee: Christine Hansen, Major Professor Donald Beitz D. Lee Alekel Kevin Schalinske

Iowa State University Ames, Iowa 2006 11

Graduate College Iowa State University

This is to certify that the master's thesis of

'~ana Chen has met the thesis requirements of Iowa State University

Signatures have been redacted for privacy

Signatures have been redacted for privacy 111

TABLE OF CONTENTS LIST OF FIGURES v LIST OF TABLES vi LIST OFABBREVIATIONS viii ABSTRACT ix CHAPTER 1. INTRODUCTION 1 Thesis Organization 1 Description of the Research Questions 1 CHAPTER 2. LITERATURE REVIEW AND RATIONALE 3 Introduction 3 Absorption, Transport, and Metabolism 4 Functions 5 Gluconeogenesis 6 formation, lipid metabolism, and erythrocyte metabolism and function 6 Nervous system, immune function, and hormone modulation 7 Amino acid metabolism 8 Food Sources and Bioavailability 8 Status Assessment 11 Direct methods 11 Indirect methods 14 Dietary intake 19 Requirement 19 Rationale 22 Objectives 23 CHAPTER 3. MATERIALS AND METHODS 24 Methods 24 Subject selection 24 Experimental design 25 Diet 2$ Sample collection 29 Sample analyses 29 Statistical analyses 32 CHAPTER 4. RESULTS AND DISCUSSION 33 Results 33 Subject characteristics 33 Diet 33 Urinary 4-PA status measure 36 Plasma PLP and 4-PA status measures 37 Plasma homocysteine measures 37 Discussion 38 Dietary factors affecting status 39 Direct measures of vitamin B-6 status 42 Indirect measures of vitamin B-6 status 44 CHAPTER 5. SUMMARY AND CONCLUSIONS 46 APPENDIX A —RAW DATA TABLES 49 1V

APPENDIX B -FORMS 59 REFERENCES CITED 71 v

LIST OF FIGURES

Figure 4.1 Urinary 4-pyridoxic acid to creatinine ratio in 16 middle aged women who consumed 4 cups soymilk or cow's milk ... 37

Figure 4.2 Plasma 4-pyridoxic acid concentration in 16 middle aged women who consumed 4 cups soymilk or cow's milk ... 3 8 V1

LIST OF TABLES

Table 2.1 Indices for evaluating vitamin B-6 status and suggested values for adequate status in adults 12

Table 3.1 Descriptive characteristics of subjects 26

Table 3.2 Experimental design 26

Table 3.3 List of prohibited foods and foods permitted only in designated amounts 27

Table 3.4 Average daily nutrient composition of 4 cups milk or soymilk consumed by 16 subjects during each experimental period 28

Table 4.1 Dietary intakes of 16 subjects during combined adjustment and washout periods, and 28-d experimental periods ... 34

Table 4.2 Dietary intakes during each period of study ... 35

Table Al Cow's milk and soymilk distribution during each experimental period 50

Table A2 Subject age, height (m), weight (kg), and initial and final BMI (kg/m2) 51

Table A3 Methionine lo