Hw many members routinel,ly prescribe
DHA in pregancy ?? What is the Role of DHA in Third Trimester??
The role of DHA in the development of brain as well as in
visual development is well established. Deficiency of (n-3) fatty acid may
affect brain development at multiple levels, from membrane biogenesis, through
gene expression, protection against oxidative stress, and altered
neurotransmission. However, whether dietary DHA is important during human brain
development is still an unresolved question.
Third trimester and the first two years of the life are
important phases of rapid brain development known as “brain growth spurt”.During
this period, polyunsaturated fatty acids of omega-3, mainly docosahexaenoic
acid (DHA) plays a critical role in the growth and development of central
nervous system of the developing baby. Additionally, DHA also confer
beneficiary effect on mothers health during pregnancyIt is one of the most
abundant constituents of brain and retina of eye and is involved in visual and
neural function and neurotransmitter metabolism. Rapid accumulation of DHA
takes place during the entire period of brain growth spurt. However, it is
required in highest concentrations (somewhere around 50-70 mg/ day) during the
third trimester. Tire accumulation of DHA into the central nervous system takes
place until about 18 months of age and both maternal DHA intake as well as
circulating DHA concentrations are important determinants of fetal blood
concentrations of DHA.Insufficient supply of DHA during this development phase
can result into serious complications of central nervous system.
As already described above, DHA is the most abundant
structural fat in the brain and eyes but it is also present throughout the
body. It is a long chain omega-3 fatty acid of 22 carbon atoms that represents
about 97% and 93% of all omega-3 fatty acids in the brain and eyes,
respectively. Natural sources of DHA are very limited and it is found in good
quantity only in some foods, particularly fatty fish. Humans are also capable
of synthesizing DHA from the essential fatty acid (EFA), a-linolenic acid
(ALA). However, dietary inclusion is important for normal growth and development.
Its deficiency can lead to a number of complications such as foetal alcohol
syndrome, attention deficit hyperactivity disorder, cystic fibrosis,
phenylketonuria, unipolar depression, aggressive hostility, and
adrenoleukodystrophy. Reduction of DHA level in brain with aging is associated
with cognitive decline and with the onset of sporadic Alzheimer disease.’
DHA is not only a key element of brain but it is also
found in high abundance in heart. Epidemiological data positively link the
consumption of fish, which are high source of DHA with reduced sudden death due
to myocardial infarction. As much as 50% reduction in death has been observed
with the consumption of 200 mg/day of DHA from fish. Furthermore, consumption
of fish oil has also shown decreases in the proliferation of tumour cells and
has a negative effect on inflammation associated with diseases like rheumatoid
arthritis and asthma. The list of beneficial effect of DHA doesn’t end here. It
also offers positive
effect on several other diseases such as hypertension,
arthritis, atherosclerosis, depression, adult-onset diabetes mellitus,
thrombosis, and some cancers.
DHA is essentially required for the healthy visual and
mental development during pregnancy and its demand increases exponentially with
the gestation age and it reaches its peak in the third trimester.5,7 The World
Health Organization (WHO) and the Food and Agriculture Organization of the
United Nations (FAO) recommends a daily intake of 100-300 mg of DFIA during
pregnancy. A regular consumption of fish or omeag-3 fatty acid supplements
during pregnancy results in increased circulating values of omega-3
polyunsaturated fatty acids in maternal blood, that is important for both fetal
and maternal health.7 During the prenatal period, DHA is supplied to the fetus
directly via placenta. Infants mainly gets DHA from breast milk however DHA
requirement in infants can also be met though supplemented formula.
Studies on the effect of maternal DHA supplementation
during the last trimester of pregnancy on their health and on the development
of infants are limited and the results from these studies are mixed. Some
studies have shown that maternal DHA supplementation have positive effects on
neonates health especially in terms of cognitive development whereas some have
shown no beneficial effect on infants development.
The role of DFIA in the development of brain as well as
visual development is well established. Deficiency of (n-3) fatty acid may
affect brain development at multiple levels, from membrane biogenesis, through
gene expression, protection against oxidative stress, and altered neurotransmission.
However, whether dietary DHA is important during human brain development is
still an unresolved question. The accumulation of DHA in the nervous tissue of
retina and brain is highest during the period of fetal development and early
infancy, its availability during this time is crucial and its deficiency may
have long term consequences for later brain function. Effect of maternal DHA
supplementation continued till the last stages of pregnancy on the visual
and/or cognitive
development after birth has been studied in few clinical
trials. Malcolm el al., studied the effect of maternal docosahexaenoic acid
(DHA) supplementation from week 15 of pregnancy until delivery in 100 women.
The outcomes from the study showed no significant difference in maturity of the
retina at one week of age. Furthermore, visual function assessed by visual
evoked potential (VEP) to flash and pattern reversal stimuli also did not show
any marked difference at birth and at 10 and 26 weeks of age, between neonates born
to mothers supplemented with fish oil versus those born to mothers supplemented
with high-olcic acid sunflower oil. However, visual development was
significantly correlated with DHA status of the infants at birth, suggesting a
possible association between the DHA status of infants at term and early
postnatal development and function of the retina.9'" In a follow up study
performed by Tofail et ah, the investigators evaluated the effect of maternal
supplementation of fish oil (1.2 g DHA+1.8 g eicosapentaenoic acid/d) or soy
bean oil (2.25 g linoleic acid+0.27 g ALA/d) during the last trimester of the
pregnancy until delivery on cognitive outcomes of infants. Cognitive
development was assessed once the infants were 10 months of age. The results
demonstrated that DHA supplementation provided no added benefit over soy-oil in
the cognitive development in infants. Both these studies demonstrated no
significant effect of maternal n-3 long chain PUFA supplementation during
pregnancy on visual function or cognitive development in the first year of
life. However, these studies were having their own difference and limitation in
the designs such as low dose and/or short duration of supplementation.9
In a study conducted by Helland et ah, the investigators
studied the effect of supplementing mothers with either cod liver oil (1.2 g
DHA/d) or corn oil (4.7 g LA)/d) from week 17-19 until the last trimester of
pregnancy and continued for three months during lactation. Investigators
reported no significant difference in electroencephalogram (EEC) maturity of
the 2-day old neonates, 3-month old infants and for novelty preference at six
and nine months of age among the two groups. However, at the age of 24, the
children of mothers who received cod liver oil showed
developing baby but also for fortifying mothers own heath
during pregnancy. Role of DHA has also been studied in conditions like prenatal
stress, pregnancy induced hypertension that usually occurs during the third
trimester of pregnancy. Additionally, there have been investigations that have
evaluated the maternal DHA supplementation continued during the end stages of
delivery on condition like postpartum depression.
As already mentioned, high accumulation of DHA in the
foetus body takes place via placenta during the third trimester of pregnancy.
This causes deficiency of DHA in mother's body. Without proper replenishment of
DHA during this period, mother's body becomes susceptible to major depressive
symptoms in the postpartum period. Results from a cross national study
performed by Joseph R. Hibbeln on rates of postpartum depression among
twenty-two countries showed that the lower the amount of DHA in the mother's
blood, the higher is the chance that she will develop postpartum depression.
These outcomes indicated that DHA supplementation especially during the later
stages of pregnancy may be important in reducing major postpartum depressive
symptoms. Keenan et al„ in their study evaluated the link between DHA
supplementation and perceived stress and cortisol response to a stressor during
pregnancy in a sample of African American women living in low-income
environments. The enrolled women were supplemented with 450 rng/day of DHA or
placebo from 16-21 weeks continued till the last trimester of pregnancy.
Pregnant women in the active group receiving DHA had a lower incidence of
reduced perceived stress and lower levels of stress hormones in the third
trimester. These results suggest a positive effect of DHA supplementation in
easing the effect of maternal stress during the third trimester.Next, studies
have also suggested that DHA may beneficially influence pregnancy induced
hypertension during the end stages of pregnancy. In a study performed by
Gerrard et ah, the investigators demonstrated that inuit women with a diet rich
in fish and sea mammals, potent source of omega-3 fatty acids, had a lower
blood pressure at the end of pregnancy and a lower incidence of gestational
hypertension compared to controls.15 Additionally, there is growing evidence
that suggests DHA role in modulating insulin resistance that might prove to be
beneficial in gestational diabetes. Furthermore, diet rich in omega-3 may be
beneficial in reducing the risk of developing pre-eclampsia during pregnancy.
Results from clinical studies suggest that the risk of developing pre-eclampsia
is 7.5 times higher in mother with extremely low levels of omega-3 fatty acids
than the mother whose levels of omega-3 are the highest. Studies have also
indicated that a diet change in favor of omega-3 from omega-6 may reduce the
risk of preeclampsia by 46%.
DHA is an important constituent of human body and is
found in high abundance in the cells of brain and retina. DHA accumulated in
high concentration during the third trimester of pregnancy that makes dietary
intervention of DHA supplementation in mothers essential and the same is
recommended by the WHO and the FAO. Although DHA role in the retina and brain
development is well elucidated in literature, the studies evaluating the effect
of DHA during the third trimester are limited. Studies on maternal supplementation
continued till the end stages of pregnancy alone have not demonstrated any
significant improvement on the visual or cognitive development in the first
year of life of infants. However, DHA supplementation during
pregnancy/lactation does offer some beneficial effect on the cognitive
function. Furthermore, role of DHA supplementation in maternal health during
third trimester has also been evaluated in few studies and the results do
suggest a beneficial effect of DHA in conditions like prenatal stress,
pregnancy induced hypertension that commonly occur during the end stages of
pregnancy and also in postpartum depression.
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