Omega-3
Fatty Acids and Children’s Health
Dr. Jamie McManus
Omega-3 fatty acids,
also known as polyunsaturated fatty acids, are essential to human health and
cannot be made by the body. For this reason, they must be obtained from the
foods we eat. Good sources of omega-3s include fatty fish and certain plant
foods, including flaxseed, chia seeds, and walnuts.
There are three major
types of omega-3 fatty acids consumed in foods and used by the body:
Alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic
acid (DHA). The body converts ALA to EPA and DHA, which are the two omega-3
fatty acids used most readily by humans. However, because this conversion is
fairly inefficient (less than 5%), dietary consumption of both DHA and EPA is
highly recommended— especially in young children in order for them to meet
their significant need for these important omega-3 fatty acids.
Research continues to
validate the important role these omega-3 fatty acids play in normal growth as
well as in the early development of a child’s brain and eyes.
Early Brain and Visual
Development
DHA and EPA are best
known for their beneficial role in protecting adults’ cardiovascular health and
in lessening inflammatory conditions. However, emerging science suggests that
DHA in particular plays an important role in early brain and visual development
in growing infants and children. In fact, DHA is the most abundant omega-3
long-chain fatty acid in the brain, and is rapidly incorporated into the
nervous tissue of the retina and brain during the last trimester of pregnancy
and continuing throughout the first few years of life. Supplementation of
infant formula with DHA has been shown to aid growth, development, and vision
in premature infants, and prenatal and infant deficiencies of DHA have been
shown to lead to brain abnormalities. [1]
Cognitive and
Behavioral Function
Beyond early
development and throughout life, DHA is believed to continue to influence brain
function by playing an important role in brain-cell membrane structure,
brain-cell receptor activity, and the production of neurotransmitters and other
brain chemicals.[2] This
has led to considerable interest in the potential role DHA may have on
cognitive development and behavioral function during childhood. A number of
research studies have examined the relationship between the levels of omega-3
fatty acids in the body and a variety of childhood disorders, including autism
and attention deficit hyperactivity disorder (ADHD).
Attention Deficit
Hyperactivity Disorder
Attention deficit
hyperactivity disorder is one of the most common childhood disorders and it
affects 5%–10% of school-age children, or 4.4 million youths ages 4–17.
Symptoms include difficulty staying focused and paying attention, difficulty
controlling behavior, and a general inability to sit still or tendency to be
hyperactive. The Centers for Disease Control (CDC) estimate that 2.5 million of
these children receive some type of medication to treat this disorder and, to
make matters worse, this condition can continue throughout life, with as many
as 70% of children diagnosed with ADHD suffering from the disorder into
adolescence and adulthood.[3]
Studies suggest that
children with ADHD may have low levels of certain essential fatty acids
(including DHA) in their bodies. In a clinical study of nearly 100 boys, those
with lower levels of omega-3 fatty acids demonstrated more learning and
behavioral problems—such as temper tantrums and sleep disturbances—than boys
with normal omega-3 fatty acid levels.[4] In
animal studies, low levels of omega-3 fatty acids have been shown to lower the
concentration of certain brain chemicals—such as dopamine and serotonin—related
to attention and motivation.[5]
Randomized clinical
trials assessing the effects of omega-3 supplementation on symptoms of ADHD
have been published. Some studies indicate supplementing a child’s diet with a
combination of long-chain fatty acids including DHA and EPA may be beneficial
for reducing symptoms of inattention and hyperactivity when compared with a
placebo,[6],[7] while other
studies have found no benefit.[8] Because
of the diversity of findings, more research is needed to draw firm conclusions.
However, researchers have proposed that future studies be designed to:
·
Better understand the
mechanism of action of omega-3 fatty acids in ADHD
·
Identify which
children with ADHD might benefit from omega-3 supplementation
·
Determine which fatty
acids—and how much—to supplement with, and
·
Pinpoint the optimal
time for intervention (e.g. prenatal, infancy, or at time of diagnosis).[9]
However, until then,
consumption of foods and supplements high in omega-3 fatty acids is a
reasonable approach for someone with ADHD.
Autism
Autism is one of a
group of disorders known as autism spectrum disorders (ASDs). Autism usually is
diagnosed by age 3 and persists throughout a person’s life. Children with
autism or other ASDs can suffer a wide array of developmental disabilities that
can cause substantial impairments in social interaction and communication, as
well as unusual behaviors and interests. Many children with ASDs also have
unusual ways of learning, paying attention, and reacting to different
sensations, and there is significant variability in severity — some children
are high functioning while others can be quite severely affected. Recent data
from the CDC’s Autism and Developmental Disabilities Monitoring Network
indicate that about 1 in 150 8-year-olds living in the United States has an
ASD. Scientists think there may be many causes that can lead to the development
of an ASD—and both genes and the environment appear to play a role.[10]
There is some evidence
that alterations in fatty acid metabolism may play a role in the
pathophysiology of autism. In one study, researchers compared the levels of
fatty acids in the blood of a group of autistic children with those in a group
of mentally challenged control subjects. Results indicated a 23% reduction in
levels of DHA in the children with autism, resulting in significantly lower
levels of total omega-3 fatty acids—without a reduction in total omega-6 fatty
acids.[11] The
reasons for the lower concentrations of DHA are not well understood, but
several hypotheses have been proposed. It may be that children with autism have
insufficient dietary intakes of DHA, may have less ability to convert ALA to
DHA, and/or have an enhanced breakdown of DHA in cell membranes.
Dietary Intake of
Omega-3s—Are Children Getting Enough?
There is growing
evidence in support of a positive relationship between omega-3 fatty acids and
many health outcomes in children (and adults as well). Changes in the diet of
Americans has dramatically changed the type of fat consumed, resulting in a
significant shift in the ratio of omega-6 fatty acids to omega-3 fatty acids,
thereby potentially changing the fatty acid composition of the brain.
Omega-6 fatty acids
such as linoleic acid (LA) are abundant in our diet, with a major source coming
from vegetable oils, which tend to be much higher in omega-6 than omega-3 fatty
acids. In the days of hunters and gatherers, the dietary ratio of omega-6 to
omega-3 fatty acids was believed to be in the range of 1:1 to 2:1. However,
over the past 50–100 years, intakes of omega-3 fatty acids such as DHA and EPA
have declined while the intake of omega-6 fatty acids has increased, such that
the ratio of omega-6s to omega-3s is now estimated in the range of 15:1 to
25:1.[12] This
ratio is important because the omega-6 fatty acid LA and the omega-3 fatty acid
ALA compete for the same enzymes that convert ALA to DHA and EPA.
Therefore, it is
believed that both excessive intakes of omega-6 fatty acids and consuming lower
amounts of omega-3s may actually diminish DHA availability in the brain. In
addition, the decreased overall intake of omega-3s means less DHA and EPA are
available for incorporation into brain-cell membranes.
Both the American
Dietetic Association and Dietitians of Canada recommend an increase in dietary
intakes of omega-3 fatty acids,[13] and
recommended intakes for omega-3 fatty acids to support optimal neuronal
functioning and overall health of children have been established by various internationally
recognized organizations.[14] Although
specific dietary requirements for DHA and EPA in children have not been
established, the National Academy of Sciences’ Institute of Medicine has
established a recommended intake for total omega-3 fatty acids as ALA,[15] with
DHA and EPA contributing 10% toward the recommended intake. For example, the
recommended intake of total omega-3 fatty acids for children ages 4–8 is 900 mg
a day, of which 90 mg may come from DHA and EPA.
Given these
recommendations, the question remains as to whether children are consuming
adequate amounts of omega-3s, especially DHA and EPA. Based on the most current
national nutrition survey findings, most infants and children are not. Data
collected from the 1999–2000 National Health Examination Survey estimated that
intakes of DHA among children 11 years old and younger to be only 20–40 mg a
day,[16] and
in a recent study published in the Journal of Nutrition, researchers quantified
the omega-3 fatty acid intake in a group of Canadian children ages 4–8. The
mean dietary intake of DHA in these children, according to this study, was only
54 mg per day.[17]
Because of the
ever-growing and emerging body of literature demonstrating the importance of
omega-3 fatty acids in proper growth and development, early brain and visual
development, and possibly in childhood conditions such as ADHD and autism, the
dietary gap between consumption and need should be filled with an increased
consumption of foods rich in DHA such as fish and seafood. However, increased
fish consumption poses additional concerns. Nearly all fish and shellfish
contain traces of mercury—and some may contain other environmental pollutants
that may pose harm to an unborn baby or to a young child’s developing nervous
system. In fact, the Food and Drug Administration (FDA) and the Environmental
Protection Agency (EPA) advise women who may become pregnant, pregnant women,
nursing mothers, and young children to avoid some types of fish and eat only
fish and shellfish that are lower in mercury.[18]
Concerns about the
safety of fish consumption coupled with inadequate dietary intakes suggest that
most children would benefit from taking a high-quality dietary supplement that
uses a pharmaceutical-grade, highly purified fish oil to deliver omega-3 fatty acids,
including plenty of DHA to support the proper development and function of the
brain and eyes.
[1] McCann
JC, Ames BN, Is docosahexaenoic acid, an n-3 long-chain polyunsaturated fatty
acid, required for development of normal brain function? An overview of
evidence from cognitive and behavioral tests in humans and animals. Am J Clin
Nutr 2005;82:281-95.
[2] Eilander
A. et al. Effects of n-3 long-chain polyunsaturated fatty acid supplementation
on visual and cognitive development throughout childhood: A review of human
studies. Prostaglandins, Leukotrienes and Essential Fatty Acids
2007;26:189-203.
[4] Stevens
LJ, Zentall SS, Abate ML, Kuczek T, Burgess JR. Omega-3 fatty acids in boys
with behavior, learning and health problems. Physiol Behav.
1996;59(4/5):915-920.
[5] Vancassel
S et al. n-3 polyunsaturated fatty acid supplementation reverses stress-induced
modifications on brain monoamine levels in mice. J Lipd Res.
2008;49(2):340-348.
[6] Sinn
N, Bryan J. Effect of supplementation with polyunsaturated fatty acids and
micronutrients on learning and behavior problems associated with child ADHD.
Dev Behav Pediatr 2007;28:82–91.
[7] Stevens
L, Zhang W, Peck L, Kuczek T, Grevstat N, Mahon A. EFA supplementation in
children with inattention, hyperactivity and other disruptive behaviours.
Lipids 2003;38:1007-1021.
[8] Voigt
RG, Llorente AM, Jensen CL, Fraley JK, Berretta MC, Heird WC. A randomized,
double-blind, placebo-controlled trial of docosahexaenoic acid supplementation
in children with attention-deficit hyperactivity disorder. Journal of
Pediatrics 2001;139:189-196.
[9] Busch
B. Polyunsaturated fatty acid supplementation for ADHD? Fishy, facinating, and
far from clear. J Dev Behav Pediatr 2007;28:139-144.
[11] Vancassel
S. et al. Plasma fatty acid levels in autistic children. Prostaglandins,
Leukotrienes and Essential Fatty Acids 2001;85(1):1-7.
[12] Simopoulos
AP. Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic
variation: Nutritional implications for chronic diseases. Biomed Pharmacother
2006;60(9):502-507.
[13] American
Dietetics Association. Position of the American Dietetics Association and
Dietitians of Canada: Fatty acids J Am Diet Assoc. 2007;107:1599-1611
[15] National
Academy of Sciences Institute of Medicine, Food and Nutrition Board. Dietary
reference intakes for energy, carbohydrate, fiber, fat, fatty acids,
cholesterol, protein and amino acids. 2002-2005.
[16] Ervin
RB, Write JD, Wang C. et al. Dietary intake of fats and fatty acids for the
United States population: 1999-2000. Advanced Data. Vital and Health
Statistics, Number 348, 2004.
[17] Madden
SM, Garrioch CF, Holub BJ. Diet quantification indicates low intakes of (n-3)
fatty acids in children 4 to 8 years old. J Nutr. 2009;139:528532.
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