Omega Fatty Acids in Brain and Neurological Health

Ronald Ross Watson, Victor R Preedy

• Publisher: Academic Press
• Year: 2019
• ISBN:
  9780128152393
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Neuroscience
• Index: Biological Sciences

Research has clearly established a link between omega fatty acids and general health, particularly cardiovascular health. Omega Fatty Acids in Brain and Neurological Health, Second Edition, illustrates the importance of omega-3 fatty acids in longevity, cognitive impairment and structure and function of the brain's neurons and also the adverse effects of omega-6 fatty acids on neurological function. This book encompasses some of the most recent research on the links between omega fatty acids and the developing brain, aging, dementia, Alzheimer's disease and multiple sclerosis, including the role of omega-3 fatty acid supplements on hippocampal neurogenesis, substantia nigra modulation, migraine headaches, the developing brain in animals, sleep and neurodegenerative diseases. This completely updated second edition focuses on the counterbalancing dietary and tissue omega-6 fatty acids as well as it studies the effects in pregnancy and early infancy, animal model studies and autoimmune neurological diseases.

• Provides a comprehensive introduction to omega-3 and omega-6 fatty acids in neurological health and directions for future research
• Features novel focus on the adverse effects of omega-6 fatty acids on neurological function and the counterbalancing of dietary and tissue omega-6
• Illustrates the importance of omega-3 fatty acids in longevity and cognitive impairment
• Features new chapters on early effects in pregnancy and early infancy, animal model studies and autoimmune neurological diseases
• Discusses links between omega fatty acids and the developing brain, aging, dementia, Alzheimer's disease and multiple sclerosis, including the role of omega-3 fatty acid supplements

Part D

Nutrients and the Brain

Chapter 20

Omega-3 Fatty Acids and Cognitive Behavior

Grace E. Giles*^,†; Caroline R. Mahoney*^,†; Robin B. Kanarek^{‡ ⁎} Cognitive Science Team, US Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, United States
^† Center for Applied Brain and Cognitive Sciences, Medford, MA, United States
^‡ Department of Psychology, Tufts University, Medford, MA, United States

Abstract

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) may influence cognition throughout the lifespan. The present chapter will discuss how n-3 PUFA supplementation may impact cognitive development in infants and children, cognitive performance in young adults, and age-related cognitive impairment in older adults. Research examining n-3 PUFA supplementation in mothers and children shows positive effects on certain aspects of cognition; however, there is less evidence to support a role for n-3 PUFAs in global indices of cognitive development. Studies in young adults are quite limited with conflicting effects of n-3 PUFAs on mood and cognitive measures, particularly executive function. In older adulthood, while epidemiological studies suggest that higher n-3 PUFA intake and plasma and/or erythrocyte levels are associated with reduced cognitive decline; results from randomized controlled trials (RCTs) are less consistent. Though evidence points to a beneficial influence of n-3 PUFAs on cognitive performance across the lifespan, the conclusions remain tenuous and a topic in need of future research.

Keywords

Polyunsaturated fatty acids; Omega-3; Cognition; Memory; Cognitive development; Alzheimer’s disease

Introduction

Omega-3 (n-3) and omega-6 (n-6) fatty acids are the main dietary components of the family of polyunsaturated fatty acids (PUFAs). The n-3 fatty-acids include alpha linolenic acid (ALA), eicosapentaenoic acid (EPA), and docohexaenoic acid (DHA), while n-6 PUFAs include linoleic acid (LA) and arachidonic acid (ARA). Since our bodies cannot synthesize these compounds, they must be obtained from our diet. The primary dietary sources of EPA and DHA are fatty fish such as salmon, herring, tuna, and halibut, while ALA comes mainly from plant sources such as canola oil, walnuts, and flax seed. The n-6 PUFAs are most commonly consumed as LA, which is found predominantly in plant oils (e.g., corn oil, sunflower oil, and soybean oil), as well as in products made from these oils.¹

Both n-3 and n-6 PUFAs are necessary for cells to maintain normal structure, function, and signal transduction. However, there is growing evidence that the ratio of n-3 to n-6 is more important than their absolute levels for these cellular processes.² For example, the ratio of n-3 to n-6 PUFA influences inflammation. Intake of n-6 PUFA increases pro-inflammatory cytokine production, whereas n-3 PUFAs reduce n-6 PUFA activity and thus decrease pro-inflammatory cytokine activity.³

The importance of n-3 PUFAs in brain function have been extensively studied in relation to psychological and neurological disorders. For instance, research indicates a beneficial influence of n-3 PUFAs on depressive symptoms in individuals with major depressive disorder although the relationship is far from understood.^4–6 The n-3 PUFAs may also benefit individuals with bipolar disorder,⁷ anxiety disorders,⁸ and attention deficit hyperactivity disorder.⁹

Despite the reported benefits of n-3 PUFAs when brain functions go awry, as in psychological and neurological disorders, less research has examined the influence of n-3 PUFAs on cognitive function in healthy individuals. The recent research has begun to fill this gap by examining how n-3 PUFAs influence cognitive development in infants and children, cognitive performance in young adults, and age-related cognitive impairments in older adults. Just as the brain changes throughout the lifespan, so too may the influence of nutrition on cognition.¹⁰ Thus, this chapter will review recent research examining the cognitive effects of n-3 intake across the lifespan.

Infants and Children

n-3 PUFAs are critical for neurocognitive development from conception through early childhood. DHA, in particular, accumulates in the brain during this time, and influences gene expression, monoamine neurotransmitter activity, and neuron growth. Higher maternal dietary intake of DHA during pregnancy and lactation results in higher DHA levels in infants.¹¹

Initial epidemiological studies explored the relationship between maternal intake of fish and other foods containing n-3 PUFAs and cognitive behavior in their offspring (see Table 1). In the majority of studies, intakes of fish by the mother during pregnancy and lactation were determined using food frequency questionnaires (FFQ) while cognitive performance in the offspring was measured with standardized tests such as the Fagan Test of Infant Intelligence, which measures novelty preference and is thought to predict IQ later in life,²⁵ the MacArthur Communicative Development Battery, which assesses infant and toddler linguistic abilities,²⁶ the Peabody Picture Vocabulary Test, which measures listening comprehension and vocabulary,²⁷ the Bayley Scales of Infant Development, which evaluates cognitive and motor development,²⁸ and intelligence tests including the Kaufman Brief Intelligence Test²⁹ and Wechsler Intelligence Scales for Children.³⁰ Most studies found that greater maternal fish intake and blood PUFA levels were associated with enhanced cognitive performance in infants and children, ranging from 6 months to 13 years.^{12–15,18,21,22} Similarly, more frequent fish intake during adolescence was associated with enhanced intelligence and academic performance,^16,17 particularly up to the recommended intake levels.¹⁹ However, it should be noted that not all studies have observed a positive relationship between early exposure to n-3 PUFAs and later cognitive functions.^20,23,24

Table 1

Epidemiological Studies Assessing the Association between Maternal and Child n-3 PUFAs and Child Cognition

Authors	n Mothers	n-3 PUFA Measurement	n Children (Female)	Age at Testing	Childhood Cognitive Measures	Results
Daniels et al.^12	7421	FFQ^a at 32 weeks’ gestation, Infant intake fish and breastfeeding at 6 and 12 months	7421 (48%)	15 and 18 months	15 months: MCDI^b 18 months: DDST^c	Higher maternal fish intake during pregnancy was associated with enhanced vocabulary comprehension and social activity at 15 months, ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Part A: Omega Fatty Acids and Brain: An Overview
• Part B: Omega Fatty Acids: Brain and Neurological Development
• Part C: Diet and Brain Disease Treatment and Prevention
• Part D: Nutrients and the Brain
• Index