Scott S Field*
Paediatrician, Huntsville Hospital, University of Alabama in Birmingham (Huntsville Campus), USA
Received date July 27, 2014; Accepted date September 09, 2014; Published date September 19, 2014
Citation: Field SS (2014) Nutritional Factors in Autism and Attention Deficit/Hyperactivity Disorder. J Nutr Disorders Ther 4:144. doi:10.4172/2161-0509.1000144
Copyright: © 2014 Field SS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Autism And Attention Deficit/Hyperactivity Disorder (ADHD) share multiple risk factors, most of which can be tied to omega-3 fatty acid metabolism and supplies of the end product, docosahexaenoic acid (DHA) for the developing brain. There has also been a significant rise in prevalence in both disorders in recent decades . The following discussion addresses the potential role of DHA deficits in the etiology of autism and ADHD as well as the potential for prevention through improved diet and/or supplements to mothers and babies at higher risk.
Transport of DHA and its precursors from a mother to her children before birth and in the first year after birth is important for normal brain development . Since DHA concentrations in fetal tissues rise sharply in the last two months of gestation and premature babies have lower levels than term babies,  prematurity limits DHA supplies for the developing brain. Prematurity is a well-known risk factor for autism and ADHD .
Apart from fish and algae-derived DHA supplements, almost all DHA for mothers and their babies has to come from conversion of the shorter chain, mainly plant-derived alpha-linolenic acid . That conversion requires a series of enzymatic steps, but the rate limiting step involves the enzyme, Delta-6 Desaturase (D6D) which is enhanced by estrogen and inhibited by testosterone . This hormonal effect results in females being born with more DHA at birth  and may explain why males are four times as likely as females to develop ADHD and autism [1,5]. Women lose DHA supplies during pregnancies [6,8]. Longer intervals (up to 3 years) between pregnancies and breastfeeding are helpful for replenishing lost DHA . Indeed, close pregnancy spacing has been found to be a risk factor for autism . Conversely, adequate child spacing along with breastfeeding is associated with increased maternal DHA stores  which may explain why being a first-born male is a risk factor even though subsequent children have older parents which is a competing risk factor .
Intrauterine transfer of DHA is also limited by gestational diabetes  which is a risk factor for both ADHD  and autism . Another risk factor at least identified for autism  and perhaps also for ADHD  is advanced maternal age which is associated with decreased D6D activity . Furthermore a Single Nucleotide Polymorphism (SNP) for the D6D gene which decreases enzyme activity has been shown to decrease DHA in breast milk . That gene is associated with ADHD  and neighboring genes are associated with autism . Thus both genes and diet can influence nutritional supplies of DHA for developing fetal and infant brains. In situations of advanced maternal age or defective D6D genes which might be reflected in maternal psychopathology such as maternal ADHD, supplemental DHA given to the mother during pregnancy and to the infant after birth may compensate for otherwise deficient maternal fetal transfer.Evidence that omega-3 fatty acids like DHA may be protective for autism include the lack of autism in an isolated community of Northern Quebec which had very high fish consumption  and the finding of more mercury in controls than in autism patients in a California study that attributed the higher mercury levels to greater fish consumption . Lower blood levels of omega-3 fatty acids have been found in autism [19-21] and ADHD [22,23] patients and some studies have found symptom improvements by using a combination of omega-3 and omega-6 fatty acids in supplemental trials [20,24-27]. Interestingly, trials using primarily DHA for supplementation have not shown benefit for symptoms [28,29]. A study that looked at risk of autism in relation to infant milk type found an increased risk with formula not supplemented with DHA compared to formula supplemented with DHA or breast milk .
An interesting finding in a British study  was an increased risk of autism in children of parents who had migrated from other countries. Fish consumption as a potential factor was not addressed, but their highest autism rates were in immigrants from the Caribbean Islands. In another study  a disproportionate number of children with at least one immigrant parent had autism, and all of them came from places where the parent said that fish was a prominent part of the diet while fish was no longer a prominent part of the diet where the child was born. What might explain this phenomenon of increased risk for autism in children of immigrant parents is that generations of people exposed to fish may have increased numbers of inefficient conversion enzyme genes because conversion is not as important in that population. When people with inefficient conversion enzymes and their children with the same inefficiencies are placed (by migration) in an environment in which they can’t rely on their diet to provide the necessary long chained omega-3 fatty acids, their brains are adversely affected with conditions like ADHD and/or autism.
Another dietary factor that can play into this is antioxidants from foods and supplements which are known to protect long-chain omega-3 fatty acids which are otherwise easily oxidized. Breath ethane, associated with omega-3 fatty acid oxidation was found in greater quantities in ADHD patients than controls .
Perhaps the most significant dietary finding in a recent clinical study  was that breastfeeding could reduce or enhance the risk for offspring developing ADHD and autism depending on variables of maternal age and maternal psychopathology. Psychopathology in that study included ADHD, autism, depression, schizophrenia, obsessive compulsive disorder, anxiety disorder, tic disorder, dyslexia, and bipolar disorder. Both ADHD and autism, in male and female children, occurred at significantly greater rates compared to controls if the mothers had psychopathology, breastfed, and were over 30 years old. If the mother did not have psychopathology, breastfeeding was protective against ADHD even when she was older than 30 years with her first-born male. When neither parent had psychopathology, breastfeeding by older mothers was more (p <0.001) protective and breastfeeding by younger mothers was borderline (P<0.1) protective for ADHD. Larger studies are needed to corroborate the data of that study, but it makes sense that not all babies, mothers, and breast milk are alike, so it is wise to separate out factors that could cause differences. Considering such differences may change nutritional approaches to health problems associated with nutrition. Conditions such as ADHD and autism may be partially preventable by treating high risk individuals with healthier diets containing more fish, fruits, and vegetables as well as with nutritional supplements such as fish oil. More studies are needed.