Fish, Omega-3 and human health

222 Pages·2005·10.395 MB·English

by  Lands, William E. M

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Fish, Omega-3 and Human Health
Second Edition
William E.M. Lands
Champaign, Illinois
Copyright © 2005 AOCS Press
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AOCS Mission Statement
To be the global forum for professionals interested in lipids and related materials through
the exchange of ideas, information, science, and technology.
AOCS Books and Special Publications Committee
M. Mossoba, Chairperson, U.S. Food and Drug Administration, College Park, Maryland
R. Adlof, USDA, ARS, NCAUR, Peoria, Illinois
P. Dutta, Swedish University of Agricultural Sciences, Uppsala, Sweden
T. Foglia, ARS, USDA, ERRC, Wyndmoor, Pennsylvania
V. Huang, Abbott Labs, Columbus, Ohio
L. Johnson, Iowa State University, Ames, Iowa
H. Knapp, Deanconess Billings Clinic, Billings, Montana
D. Kodali, Global Agritech, Plymouth, Minnesota
T. McKeon, USDA, ARS, WRRC, Albany, California
R. Moreau, USDA, ARS, ERRC, Wyndoor, Pennsylvania
A. Sinclair, RMITUniversity, Melbourne, Victoria, Australia
P. White, Iowa State University, Ames, Iowa
R. Wilson, USDA, REE, ARS, NPS, CPPVS, Beltsville, Maryland
Copyright ©2005 by AOCS Press. All rights reserved. No part of this book may be repro-
duced or transmitted in any form or by any means without written permission of the pub-
lisher.
The paper used in this book is acid-free and falls within the guidelines established to ensure
permanence and durability.
Library of Congress Cataloging-in-Publication Data
Lands, William E. M., 1930–
Fish, Omega-3 and human health / by William E.M. Lands.-- 2nd ed.
p. cm.
Includes bibliographical references and index.
ISBN 1-893997-81-2 (alk. paper)
1. Fish as food. 2. Heart--Diseases--Nutritional aspects. 3.
Essential fatty acids in human nutrition. I. Title.
QP144.F56L36 2005
616.1'20654--dc22
2005002993
CIP
Printed in the United States of America.
08 07 06 05 04 5 4 3 2 1
Copyright © 2005 AOCS Press
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Afull, balanced life
Has many events
Known and unsensed
Transient and enduring.
We treat and prevent
With mineral and nutrient
From seas and lands
Of fish and man.
Copyright © 2005 AOCS Press
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Contents
Foreword
Preface
Introduction
Part 1. Relating Diet to Disease
1 Epidemiology and Curiosity
2 Foods, Drugs, and Disease Mechanisms
3 Essential Fatty Acids
4 Common Factors in Heart Disease, Heart Attacks, and Strokes
5 Heart Disease: Atherosclerosis and Serum Lipids
6 Heart Attack: Coronary Thrombosis
7 Vasospasm: Cardiac Output and Coronary Flow
8 Strokes
9 Hypertension
10 Immune Responses
11 Cell Proliferation and Cancer
Part 2. Metabolic Differences Among Polyunsaturated Fatty Acids
12 Maps and the Unknown
13 Acyl-CoA Pathways
14 Pathways to Prostaglandins
15 Prostaglandin Formation Following Changes in Diet
16 Pathways to Leukotrienes
Part 3. Choosing Diets
17 Polyunsaturated Acids in Tissues and Foods
18 Overall Supply of n-3 Fatty Acids
19 Alternative Diets
Glossary
About the Author
Copyright © 2005 AOCS Press
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Foreword
I am pleased to recommend Fish, Omega-3 and Human Health to all readers inter-
ested in the basis of disease and nutritional strategies that can be used to support bet-
ter health. Valuable insights can be gained on many diverse topics. What is amaz-
ing is that everyone, from the layman interested in good nutrition to research scien-
tists who specialize in essential fatty acids, can gain valuable insights from this
book. Graduate students will find many directives for important thesis projects for
many years to come. Bill Lands unfolds his story in a most readable manner, start-
ing from the beginning and gaining technical force as he finishes chapters with tech-
nical sections. He has a passion for the prevention of eicosanoid-mediated disease;
disease that he convincingly shows can be prevented or diminished by more careful
selection of the foods that we eat. His thesis is that we must better balance n-3 and
n-6 fatty acid intake to moderate an over active eicosanoid system that is leading to
the development of many of the chronic inflammatory diseases that plague the pre-
sent day industrialized world. Chapters 13 and 14 were especially delightful for me,
his insightful analysis of fatty acid and lipid metabolism and eicosanoid formation
and regulation. His perspective and broad scope is one gained from the brilliant
research career of a pioneer in these areas.
Norm Salem, 2004
2002 AOCS/Supelco Research Awardee
Copyright © 2005 AOCS Press
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Preface to the Second Edition
This second edition of Fish, Omega-3 and Human Health reaffirms that essential
fatty acids in the foods we eat form hormones that have powerful effects on human
life. Many find it hard to believe that a simple change of diet can affect so many
things in their lives. This second edition adds information to help readers sense the
slow shift in attitudes about the relationship between foods and disease.
Since the first edition in 1986, the names for n-3 and n-6 structures became
known as omega-3 and omega-6. However, understanding of how food choices
affect so many serious aspects of life was delayed by two general attitudes. One atti-
tude had faulty logic in interpreting some associated markers as causal mediators of
disease and death, and the other attitude was a bias for curative/treatment interven-
tions that neglected preventing initial dietary causes of disease and death. This edi-
tion expands the glossary of words and concepts to help readers recognize how spe-
cific nutrient imbalances in our normal diets can contribute to disease and death.
I thank the various editors who have invited me to reflect on my absorbing and
enjoyable career of discovery, especially Mary Lane who assured me that I could
update this book and Howard Knapp and Jodey Schonfeld who helped me be diplo-
matic. I also thank the AOCS which awarded me the 1997 Supelco/Nicholas Pelick-
AOCS Research Award.
Above all, I thank the friends who shared my curiosity and helped me find
words to speak of my own slow step-by-step growth in understanding: Norberta
Schoene, Etienne Lamoreaux, Pat Springer, Bill Smith, Lenny Rome, Martin
Hemler and Rich Kulmacz. Also, I thank the many colleagues who published the
hundreds of interesting research reports that make Fish, Omega-3 and Human
Healtha rich field of discovery.
I hope that the new information will help people build a positive attitude toward
changing harmful food habits and building a better quality of life. Preventing chil-
dren from developing nutritional imbalances before the problems become severe is
likely every parent’s goal. My parents have died, and another generation has arrived
since the first edition. I hope that some of what we now know will help my four
great-grandchildren have a long healthy life. May this small book help all who read
it enjoy a long, healthy life with their families filled with understanding and love.
William E. M. Lands
Copyright © 2005 AOCS Press
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Preface to the First Edition
Curiosity is the beginning of understanding, and a steady pursuit of our questions
seems to always lead us into new adventures and new understandings. When I was
a young child, my mother and father explained to me why eating undercooked pork
was often not safe. In doing so, they created for me a new understanding of how the
custom of forsaking this form of food had health benefits for the tribes who followed
it. My parents also told me of some benefits of that “daily spoon” of fish liver oil that
we took before the days of coated vitamin pills. Over the years, they somehow con-
vinced me to think about what would be a moderate, balanced daily diet. The more
I think about our “normal” diets and our “normal” ways of life, the more curious I
am about what is normal.
Now I can no longer turn to my parents for advice because in the “normal”
course of events my father died (as did his father) of a heart attack before the age of
65 and my mother is paralyzed and without speech as a result of a cerebral stroke
many years ago. Stories that they can no longer tell me are steadily filling new
books on the shelves of our libraries, and in them I can find new ways of following
the questions “What if?” and “How come?”
This book is dedicated to all those who sought answers and shared their under-
standing with the rest of us who want to know. I share their stories with you and my
children and my grandchildren.
William E. M. Lands
Copyright © 2005 AOCS Press
introduction 3/29/05 6:40 AM Page xiii
Introduction
Eicosanoids
Many disorders of human health are linked to an imbalanced overproduction of hor-
mone-like materials derived from the polyunsaturated fatty acid, arachidonate. This
twenty-carbon fatty acid is converted in our bodies to hormone-like materials called
eicosanoids (Fig. I-1). An overproduction of eicosanoids occurs in many health dis-
orders such as thrombosis or asthma. Medications can slow down the overproduction
of eicosanoids, decreasing the severity of the disorders and some unpleasant symp-
toms. Our food intake also can affect that undesired overproduction. This book
examines some dietary ways to regulate eicosanoid production and action to give us
some of the benefits associated with certain medical treatments.
The quickest and most dramatic relief from the effects of eicosanoid overpro-
duction is usually obtained with specialized medicines that inhibit the enzymes that
produce eicosanoids. With this inhibition, the medicines rapidly establish a new bal-
ance among the hormone-like materials in our tissues. This effect is important in
treating an acute health crisis when we want immediate relief. Also, some of the syn-
thetic drugs may be used either on a short-term or long-term basis when arranging
for the prophylactic (preventive) treatment of people who are at risk of disorders
related to an undesirable overproduction of the eicosanoids.
Preventing Diet-based Disease
This book focuses on a long-term approach to prophylactic treatment. Because
eicosanoids are derived only from dietary fatty acids, a long-term preventive
approach is proposed that involves considering the type of fat consumed in daily
diets. Proper nutrition and food selection can be important in programs for preventive
medicine or health maintenance. There are many ways in which careful planning of
the daily balance in our various foods can improve our health. With what is now
known about eicosanoids, new programs that recognize the dietary origins of the
arachidonate in our tissues can be designed to change the balance of formation
Fig. I-1.Eicosanoids from arachidonate.
Copyright © 2005 AOCS Press
introduction 3/29/05 6:40 AM Page xiv
among eicosanoids in our bodies over a long period without the use of drugs. Some
people achieve this type of health maintenance program when following their tradi-
tional cultural food habits.
Arachidonate is an essential fatty acid that we cannot make on our own and can
obtain only through the foods we eat. Often, arachidonate (20:4n-6)* is derived from
a shorter acid of the (n-6) type of polyunsaturated fatty acid, linoleate (18:2n-6),*
that animals and humans obtain from plants (Fig. I-2). (*The number notation 20:4n-
6 indicates the size of the fatty acid, 20 carbons; the number of double bonds, 4; the
location of the last double bond, n-6. With linoleate there are 18 carbons, 2 double
bonds, and the last double bond is at the n-6 position. [Illustrations of these structures
are in the Glossary.])
Competition by n-3 and n-6 Acids
Our tissues can convert dietary linoleate (n-6) into a variety of polyunsaturated fatty
acids, all of the n-6 type. A closely related group of fatty acids, the linolenate (n-3)
type, also comes to us through diet. An important part of the story discussed in this
book relates to the balance between these two kinds of polyunsaturated fatty acids,
the n-6 and n-3 types. Both types come into our food chain from plant origins, and
they compete with each other for our enzyme systems. Understanding the competi-
tions leads us to consider four dietary approaches to antagonize or decrease imbal-
anced formation of n-6 eicosanoids from arachidonate. They are mentioned only
briefly here, and the basis for their health effects is discussed in detail later in this
book.
One early suggestion for shifting the balance of eicosanoids was to eat large
amounts of vegetable oils containing linoleate (18:2n-6) as in reports of Dayton et al
(1966) and Galli et al (1981). This approach was based initially on an interest in low-
ering high blood cholesterol levels and on very preliminary evidence that megadoses
or supraoptimal amounts of linoleate (11-15% of the daily energy intake) might
antagonize eicosanoid formation. The proposed antagonism (represented in Fig. I-3
by the line marked “1”) raised hopes for “megadose” linoleate treatments, but it now
seems unlikely. In contrast, drugs and eicosapentaenoate (20:5n-3) do block this con-
version.
Since the amount of the essential fatty acid, linoleate (18:2n-6) adequate for the
needed eicosanoid formation seems to be less than 1% of daily energy intake (1
en%), a second approach could be to reduce the average daily intake of linoleate
from current high amounts to a level near 1 en%. The lower intake might keep the
Fig. I-2.Arachidonate from linoleate.
Copyright © 2005 AOCS Press
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Fig. I-3.Competition between n-3 and n-6 types of polyunsaturated fatty acids and drug
action can both diminish n-6 eicosanoid formation and action.
proportion of n-6 acids in tissue membranes at moderate values and cut the likeli-
hood of overproducing eicosanoids from arachidonate. A third approach is to con-
sume vegetable oils that contain as much linolenate (18:3n-3) as linoleate (18:2n-6).
It is based on well-established results indicating that competitive antagonism by the
n-3 fatty acids decreases the conversion of dietary linoleate (18:2n-6) to tissue
arachidonate (20:4n-6) as well as increasing eicosapentaenoate that antagonizes
oxidative conversion of 20:4n-6 to eicosanoids (noted by lines marked 2 and 3,
respectively, in Fig. I-3).
The fourth approach is to eat fish or fish oils. It is based on competitive concepts
similar to the third approach, but has an additional strength due to the greater com-
petitive effectiveness of the longer, more unsaturated analogs of n-3 fatty acids
(20:5n-3 and 22:6n-3) that occur in maritime foods, such as fish, shrimp, and sea-
weed. From this last alternative comes the title of this book.
PUFA and Human Health
This book introduces readers to the natural origins of polyunsaturated fatty acids in
dietary fat and offers some basic insights into three general processes by which their
competitive interactions affect human health: membrane structures, eicosanoid
actions and gene expression (Fig. I-4).
1. Tissue EFA form specific lipid-protein membrane complexes needed for cellular
structures at specific stages of tissue development and differentiation. In particu-
lar, adequate supplies of EFA are vital during brain and retina development. A
growing realization of the importance of EFA transfer from mothers to infants is
now alerting the health community to possible nutritional deficits of n-3 EFA
Copyright © 2005 AOCS Press