Vitamin B-6 Metabolism in Pregnancy, Lactation, and Infancy

Daniel J. Raiten

• Publisher: CRC Press
• Year: 2021
• eBook ISBN: 9781000446302
• Edition: 1
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

This book provides a comprehensive review of our knowledge of vitamin B-6 requirements and metabolism throughout pregnancy and lactation. It concentrates on two primary points: adequacy of available methodologies and a presentation of the extant knowledge on vitamin B-6 metabolism and requirements in pregnancy, infancy, lactation, and in women of childbearing age. Many of the chapters offer new perspectives on how decisions have been and are being made with regard to the establishment of dietary recommendations about vitamin B-6 and the adequacy of research to support these decisions.

Chapter 1

Historical Perspectives on Our Understanding of Vitamin B-6 in Pregnancy, Lactation, and Infancy

Avanelle Kirksey

CONTENTS

I.	Vitamin B-6 in Pregnancy
	A. Treatment of Hyperemesis Gravidarum
	B. Pregnancy Requirements
	C. Relation to Pregnancy Outcome
	D. Methodological Problems in Assessment
	E. Summary
II.	Vitamin B-6 in Lactation
	A. Concentration of Vitamin B-6 in Milk
	B. Factors Related to Vitamin B-6 Content of Milk
	C. Suppression of Lactation
	D. Summary
III.	Vitamin B-6 in Infant Nutrition
	A. Convulsive Seizures
	B. Vitamin B-6 Dependency
	C. Central Nervous System Development and Function
	D. Infant Requirements
	E. Summary

References

“In the field of observation chance favors only the prepared minds.”

Pasteur’s maxim

This chapter presents a chronological overview of some of the events that have led to our present understanding of the need for and functions of vitamin B-6 in the nutrition of pregnancy, lactation, and infancy. The first suggestion of a human need for vitamin B-6 was made by Spies et al.¹ in 1939. This was based on observations that symptoms in adults characterized by extreme nervousness, irritability, insomnia, weakness, and difficulty in walking responded favorably within 24 h to vitamin B-6 therapy. This study and subsequent clinical investigations were made possible by the elucidation of the chemical structure of vitamin B-6 and its synthesis in 1939.^2,3

I. VITAMIN B-6 IN PREGNANCY

A. TREATMENT OF HYPEREMESIS GRAVIDARUM

Three years after synthetic vitamin B-6, i.e., pyridoxine hydrochloride (PN-HCl) became available, it was used empirically by Willis et al.⁴ in the treatment of hyperemesis gravidarum, resulting in almost complete relief from nausea and vomiting. Based on these findings, several other investigators in the 1940s^{5, 6, 7} used PN-HCl therapy experimentally and with success in the treatment of nausea and vomiting of pregnancy. The history of the use of vitamin B-6 therapy in the treatment of this disorder of pregnancy is summarized in Table 1. As can be seen, the dosages of PN-HCl used in different investigations varied in amounts and in frequency and methods of administering, i.e., per os, intravenous, and intramuscular. Only one report⁸ was found that indicated failure in the use of pyridoxine therapy in the treatment of hyperemesis gravidarum.

Unfortunately, investigations that were conducted in the 1940s suggesting efficacy of PN-HCl in the treatment of nausea and vomiting of pregnancy were not randomized controlled trials. Even though some investigators^6,8 indicated the need for controlled clinical trials with a larger series of patients, such studies were not forthcoming for several years.

From 1956 to mid-1983, Bendectin was widely used as an antiemetic drug in the U.S. This drug contained 10 mg each of PN-HCl, doxylamine succinate, and dicyclomine-HCl (deleted in 1977). Bendectin was removed from the market by the Food and Drug Administration in 1983 after it was suspected (but never proved) to be a teratogen causing congenital heart defects and limb reduction.⁹

In 1979, the Council on Drugs of the American Medical Association¹⁰ issued a statement that there was no solid evidence that vitamin B-6 is an effective agent in the treatment of nausea. It was not until 1991, almost 50 years after the study of Willis et al. that the first randomized, double-blind, placebo-controlled procedure was used to evaluate the efficacy of PN-HCl in the treatment of nausea and vomiting of pregnancy.¹¹ Oral administration of PN-HCl at the level of 25 mg every 8 h for nine doses did not significantly improve symptoms in patients with mild to moderate nausea, but was effective in severe cases and significantly reduced vomiting in all patients treated. The underlying defect in hyperemesis gravidarum is not known.

B. PREGNANCY REQUIREMENTS

The national alarm and controversy about malnutrition in the 1940s was centered on the B vitamins and the lack of controlled experimental studies of human needs.¹² In 1946, a review of recent work concerning nutrient requirements for human pregnancy and lactation¹³ indicated the lack of any information about vitamin B-6 needs except for its therapeutic use in hyperemesis gravidarum.

During the late 1940s and early 1950s, evidence was presented to show biochemical disturbances in vitamin B-6 metabolism beginning in the first trimester of pregnancy. McGanity et al.¹⁴ observed that fasting blood urea levels were lower in pregnant than nonpregnant women and that the levels were lowest in hyperemesis gravidarum. Vitamin B-6 insufficiency was suspected because urea levels could be restored to normal by PN-HCl supplements. Other researchers^15,16 found that urinary excretion of xanthurenic acid, following a test dose of tryptophan, was appreciably higher in pregnancy than nonpregnancy, and that levels were re...

Table of contents

• Cover
• Title Page
• Copyright Page
• Foreword
• Acknowledgments
• Dedication
• The Editor
• Contributors
• Table of Contents
• Chapter 1 Historical Perspectives on Our Understanding of Vitamin B-6 in Pregnancy, Lactation, and Infancy
• Chapter 2 Dietary Assessment
• Chapter 3 Biochemical Methods for Status Assessment
• Chapter 4 Animal and Mathematical Models of Vitamin B-6 Metabolism
• Chapter 5 The Role of Vitamin B-6 in Central Nervous System Development: Neurochemistry and Behavior
• Chapter 6 Vitamin B-6 Metabolism and the Maternal-Fetal Relationship
• Chapter 7 Vitamin B-6 in Infancy: Requirements and Current Feeding Practices
• Chapter 8 Vitamin B-6 Needs, Status, and Dietary Recommendations for Lactating Women
• Chapter 9 Vitamin B-6 Status and Requirements of Women of Childbearing Age
• Chapter 10 Clinical and Metabolic Considerations Affecting Vitamin B-6 Status of Premature Infants
• Chapter 11 Therapeutic Uses of Vitamin B-6 in Clinical Disorders of Infancy and Childhood
• Index