Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing

Ellen Mozurkewich; Deborah R Berman; Julie Chilimigras

Expert Rev of Obstet Gynecol. 2010;5(1):125-138.

Nomenclature

The LC-PUFA are comprised of 20 or more carbon atoms and three or more double bonds.^[3] They are classified as omega-3 or omega-6, based on the location of the last double bond in relation to the terminal methyl end of the molecule.^[4] LC-PUFA are synthesized from the parent omega-3 and omega-6 essential fatty acids, α-linolenic acid and linoleic acid, which are converted to omega-3 and omega-6 LC-PUFA, respectively, through a process of enzymatic desaturation and elongation.^[5] In the omega-3 series, α-linolenic acid is converted to the LC-PUFA, eicosapentaenoic acid (EPA), which may in turn be converted to docosahexaenoic acid (DHA). Similarly, in the omega-6 series, linoleic acid is converted to arachidonic acid (Figure 1). α-linolenic acid and linoleic acid are essential fatty acids, meaning that they cannot be synthesized by the human body. Fatty acids in the omega-3 and omega-6 series cannot be interconverted.^[5] Dietary sources of α-linolenic acid, the precursor of DHA and EPA, include walnuts, rapeseed and flaxseed oils, and green leafy vegetables. However, because of the relative inefficiency of this conversion process in humans, most of the omega-3 LC-PUFA are obtained from dietary ingestion of fish and seafood.^[4]

(Enlarge Image)

Figure 1.

Conversion of linoleic acid and α-linoleic acid to long-chain polyunsaturated fatty acids.

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Table 1. Omega-3 fatty acids and industrial contaminants in commonly eaten fish and shellfish.
Type	EPA + DHA (mg/serving) (oz)	EPA + DHA (mg/100 g) (3.5 oz)	Mercury (µg/g) (ppm)	PCBs (ng/g) (ppb)
Anchovy	1165 (2)	2055	< 0.05
Catfish, farmed	253 (5)	117	< 0.05	< 50
Cod, Atlantic	284 (6.3)	158	0.10
Fish burger (fast food)	337 (2.2)	546	< 0.05	8
Fish sticks, frozen	193 (3.2)	214	< 0.05
Halibut	740 (5.6)	465	0.25
Herring, Atlantic	1712 (3)	2014	< 0.05
Mackerel, Atlantic	1059 (3.1)	1203	0.05
Mackerel, King	618 (5.4)	401	0.73
Mahimahi	221 (5.6)	139	0.15
Pollock, Alaskan	281 (2.1)	468	< 0.05
Salmon, farmed	4504 (6)	2648	< 0.05	15–51
Salmon, wild	1774 (6)	1043	< 0.05	0.5–5
Sardines	556 (2)	982	< 0.05	22–57
Shark	583 (3)	689	0.99
Snapper	546 (6)	321	0.19
Swordfish	868 (3.7)	819	0.98
Trout	581 (2.2)	935	0.07	11
Tuna (light/skipjack)	228 (3)	270	0.12	45
Tuna (white/albacore)	733 (3)	862	0.35	100
Clams	241 (3)	284	< 0.05	2–3
Crab	351 (3)	413	0.09	6
Lobster	71 (3)	84	0.31
Mussels	665 (3)	782	< 0.15	0.8–7
Oysters	585 (3)	688	< 0.05	0.8–17
Scallops	310 (3)	365	< 0.05
Shrimp	267 (3)	315	< 0.05	0.2–2

DHA: Docosahexaenoic acid; EPA: Eicosapentaenoic acid; PCB: Polychlorinated biphenyls; ppb: Parts per billion; ppm: Parts per million.
Adapted from.^[101]

Table 2. Results of clinical trials of omega-3 fatty acid supplementation.
Parameter	Results
Preterm birth:
< 37 weeks	No benefit*
< 34 weeks	Likely benefit^§
Intrauterine growth restriction (small for gestational age)	No benefit
Preeclampsia	No benefit
Perinatal depression:
– Prevention	No benefit
– Treatment	Conflicting results^¶
Neurodevelopmental outcomes:
– Term	Conflicting results
– Preterm	Conflicting results
Prevention of allergic disease	Conflicting results

*The majority of the available clinical trials show no benefit for the intervention.
^§The majority of the available clinical trials show a benefit for the intervention.
^¶Clinical trial results are mixed, with some trials showing benefit and others not.

Box 3. Biologic activities of omega-3 fatty acids.
Decrease proinflammatory cytokine production Precursors of resolvins and neuroprotectins Improve membrane fluidity May counter or promote apoptosis, depending on circumstance Regulate gene expression Act as antioxidants Quicken neurotransmission Modulate intracellular signaling

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