Omega-3 & Omega- 6; Long-chain polyunsaturated fatty acids (LC-PUFAs)

1. )

2. Background and Chemistry
• Fat is the most energy dense macronutrient
and has important functions, not only as a
source of energy but also as a crucial
component of cell membrane structure,
healthy brain and nervous system function.
• The quality of fat consumed is therefore very
important, particularly in early life,
pregnancy and lactation.

3. Classification of fats
Fats are classified into 4 categories as follows:
1. On the basis of chemical composition
2. On the basis of fatty acids
3. On the basis of requirement
4. On the basis of sources

4. Classification: On the basis of
requirement
1. Essential fatty acids
• Fatty acids which are essential to be taken in our
diet because they cannot be synthesized in our
body. Linoleic, linolenic and arachidonic acids.
2. Non-essential fatty acids
• Fatty acids which can be synthesized by the
body and which need not be supplied through
the diet. Palmitic acid, oleic acid and butyric
acid.

5. Classification: On the basis of fatty
acids
• 1. Saturated fatty acids
• 2. Unsaturated fatty acids
I. Monounsaturated fatty acid (MUFA):
II. Polyunsaturated fatty acid (PUFA):
A. Omega-3: α-linolenic acid (ALA) [found in plant oils],
eicosapentaenoic acid (EPA), and docosahexaenoic
acid (DHA) [both commonly found in marine oils].
B. Omega-6: also known as linoleic acid

7. Classifications of polyunsaturated
fatty acids
• Based on the length of their carbon backbone,
they are sometimes classified in two groups:
• Short chain polyunsaturated fatty acids (SC-
PUFA), with less than 18 carbon atoms.
• long-chain polyunsaturated fatty acids (LC-
PUFA) with more than 18 carbon atoms.

8. polyunsaturated fatty acids
• The PUFAs linoleic acid (LA) and α-linoleic acid (ALA) are
essential fats, meaning that they must be regularly supplied
from external dietary sources as they cannot be synthesized
by the human body.
• LA and ALA undergo metabolic conversion
• Arachidonic acid (ARA – derived from LA) and
• Eicosapentaenoic acid and Docosahexanoeic acid (EPA &
DHA respectively – derived from ALA).
• Some physiological functions are directly attributable to these
LC-PUFA's while other functions and biological effects require
the formation of their active lipid metabolites (eicosanoids &
docosanoids).

9. long-chain polyunsaturated fatty
acids (LC-PUFA)
• LC-PUFAs can be further metabolised into short-lived lipids
known as eicosanoids & docosanoids which influence
physiological systems and clinical outcomes.
• Their effects on human health depend on the type of
eicosanoid produced and can influence both positive and
negative health outcomes.
• For example an excessively increased ratio of omega-6 (n-6)
to omega-3 (n-3) fatty acids has been suggested to promote
inflammation and inflammatory-related diseases through the
production of n-6-derived proinflammatory eicosanoids.

10. Eicosanoids
• LC-PUFA’s can undergo further metabolism to
form eiconsanoids & docosanoids, which are
highly potent, short-lived, biologically active lipids.
• Eicosnaoids include several families:
prostaglandins, prostacyclins and thromboxanes
as well as leukotrienes and hydroxl fatty acids.
• Eicosanoids are involved in platelet
aggregation, chemotaxis and cell growth.

11. Docosanoids
• Docosanoids include resolvins, protectins
and maresins.
• Docosanoids are actively involved in
physiological processes similar to
eicosanoids, and more specifically, in the
regulation and resolution of inflammatory
processes, in which n-3 LC-PUFAs play an
important anti-inflammatory role.

12. Physiological Roles of LC-PUFAs
Energy supply
Membrane Structure and Function
of in the brain and retina & platelet
Influence immune response, cell
differentiation & growth and
regulate gene transcription.
Influence vascular, neural
and immune function

13. Dietary Sources
• While fish is considered one of the best
sources of omega-3 LC-PUFA, it is by no
means the only source.

14. Dietary Sources
• Fish
• Marine species, especially from cold waters,
contain high amounts of LC-PUFA’s .
• A recent systematic analysis, of more than
1.5 million individuals representing 113 out of
187 countries (82% of the world's
population) found that more than 80% of the
world's population has a mean omega-3
seafood intake below the recommended
levels of 250 mg/d for adults.

16. Meat
• The fatty acid composition of meat depends primarily on the
type of animal.
• In ruminants, such as cows, more than 90% of the
unsaturated fatty acids are hydrogenated to saturated fatty
acids in the rumen.
• Beef therefore, contains higher amounts of saturated fatty
acids than the meat of non-ruminant animals.
• The content of LC-PUFA's and their precursors is
considerably lower compared to the LC-PUFA content of oily
fish.
• ARA is the LC-PUFA that is most predominantly present in
meat.

18. Eggs and Milk
• Egg yolk consists of approximately 30% fat,
mostly saturated (SFA) and monounsaturated fatty
acids (MUFAs), but also a considerable amount of
LA.
• Milk fat also consists mostly of SFA's and MUFA's
and only contains small amounts of PUFA’s.
• There are no appreciable contents of LC-PUFA's
in cows’ milk and other dairy products.

20. Plants
• Plants store energy as oil in their seeds.
• The FA composition of seed oils varies
widely and typically one FA dominates.
• Plant-derived foods are not sources for
LC-PUFA's, but for the precursor fatty
acids linoleic acid and α-linolenic acid.

22. Health Benefits in Infants
• LC-PUFAs are thought to have many health
benefits both in the short and long-term.
• While it is difficult to pinpoint direct cause and
effect, studies suggest LC-PUFAs may improve
visual acuity, cognitive development and
allergy outcomes as well as support immune
function and improve markers of
cardiovascular disease.

23. Cognitive Development
• Breastfeeding is associated with an advantage of
2.2 IQ points adjusted for maternal IQ.
• It has been hypothesized that the observed
difference in cognitive outcomes between
breastfed and formula fed infants may be
attributable at least in part to the provision of n-6
and n-3 LC-PUFA's that are present in breastmilk
but not in conventional infant formula.
Health Benefits

24. Allergy and Immune Function
• It has been hypothesized that PUFA status in
infancy may have a protective effect on the
development of allergies.
• Results from observational studies show a
clear association between low DHA content of
breastmilk and an increased risk of atopic
disease in the infant.
Health Benefits

25. Visual Acuity
• Development of visual acuity in infancy reflects
nervous system development, and not refractive
errors that are correctable with eyeglasses.
• Breastfed infants having received DHA-enriched
complementary foods had more mature visual
evoked potentials at 9 and 12 months of age
compared to the control group.
Health Benefits

26. LC-PUFA in Breastmilk and BMS
• Fat is the largest contributor to the caloric
content of breastmilk and is the most variable
concentration of all macronutrients .
• Concentration varies between women as
well as between feeds and is influenced by
stage of lactation, total milk volume and
maternal nutrition.

27. • Infant intake of LC-PUFA’s and their precursors is
derived from maternal diet or body stores.
• Additionally, LC-PUFA metabolites are formed in
relatively small amounts from endogenous PUFA
conversion.
• Studies show that 30% of linoleic acid (LA)
present in breastmilk was derived from dietary
sources and 1.2% ARA originated from
endogenous conversion of LA.

28. • Sufficient dietary intake is also important to ensure
adequate intake in infants. Supplementation with
preformed LC-PUFA’s has been shown to increase
their concentrations in breastmilk in very short periods
of time.
• Supplementation of DHA in lactating women for 14
days demonstrated that approximately 20% of DHA
was secreted into breastmilk indicating that dietary
DHA is an important determinant of DHA content in
breastmilk.
• Physicians should counsel mothers to ensure
sufficient dietary LC-PUFA intake in order to support
optimal infant growth and development.

29. LC-PUFA and Lactational Changes
Over Time
• The composition of fatty acids in breastmilk change over time.
• The proportions of both n-6 and n-3 LC-PUFA’s decrease
considerably within the first month of lactation with ARA
decreasing ~ 38% and DHA by as much as 50%.
• This decrease does not necessarily imply a drop in total LC-
PUFA supply as total milk fat increases over time, therefore
the total amount of LC-PUFA’s secreted into breastmilk
remain relatively stable.
• The high percentage of LC-PUFA’s in colostrum may be
explained by the low volume of milk consumed by neonates
during a time of rapid growth .

30. • After the large changes seen in DHA and ARA
concentration during the first month concentrations
remain relatively stable up to 12 months of age.
• DHA supply from breastmilk was determined to be
approximately 50 mg/day during the first three months
of life, dropping to around 33 mg/day by six months.
• These values are significantly lower than the advised
intake of 100 mg/day and highlight the potential
benefits of DHA supplementation.
• While ARA content also decreased over the first six
months, supply was considered to be adequate.

31. Recommended LC-PUFA Intake for
Lactating Mothers
• Sufficient maternal intake of DHA is important for
lactating women to ensure that infants receive the
high amount of LC-PUFA required for the rapidly
developing central nervous system.
• To ensure an adequate supply of DHA to infants
and to maintain maternal DHA status it is
recommended that lactating mothers consume at
least 200-300 mg/day of DHA .

32. • A daily supply of 200 mg DHA results in a
breastmilk content of 0.3%, providing the infant
with a total daily supply of 100 mg DHA.
• To achieve nutrient recommendations women
should consume a minimum of two portions of
fish per week, including at least one portion of
oily fish.
• Women who do not eat fish are encouraged to
take good quality fish oil supplements.

33. LC-PUFA Content of Breastmilk
Substitutes
• LC-PUFA enriched formulae are common
worldwide.
• Most formulae contain 0.2-0.4% DHA of total
FAs and 0.35-0.7% of total FAs as ARA.
• These values are based on worldwide
averages of DHA and ARA in breastmilk as
well as on expert recommendations on
adequate intakes.

34. Codex Alimentarius
• The Codex Alimentarius lists the LC-
PUFA precursors LA and ALA as essential
components of infant formulae.
• Maximum values are not specified, but the
ratio of LA:ALA should lie between 5:1 and
15:1.

35. European Commission
• In 2016 the European Union (EU) stipulated
that addition of much higher levels of DHA
(20-50 mg per 100 kcal, equivalent to about
0.5-1 % of FAs) shall become mandatory for
infant and follow-on formulae in the EU,
however no requirement of the addition of
ARA was defined.

36. Changing LC-PUFA Requirements in
Infancy
• In the absence of firm evidence to define
reference nutrient intakes for newborns
and young infants, breastmilk may serve
as a model to define appropriate ARA and
DHA intakes,

37. • International authoritative bodies have
proposed adequate intakes (AI's) for older
infants from 6-24 months as there is
insufficient evidence to set dietary reference
intakes (DRI's) for infants and children.
• Beyond this age, advice for children should
be consistent with advice for the adult
population (i.e. 250 mg/day EPA+DHA or 1-2
portions of oily fish per week).

38. LC-PUFA Requirements in Infancy

39. Complementary Feeding
• In Complementary Feeding, delaying the introduction of fish
does not appear to reduce the risk of allergy development.
• However, it can lead to a significant reduction of n-3 LC-PUFA
intake which in turn may contribute to adverse health
outcomes.
• In fact, studies have shown that, following the introduction of
complementary foods, ARA and DHA intake for infants in
both low and high income countries often lies below nutrient
intake recommendations.

40. • In low income countries, traditional complementary
foods are low in LC-PUFA's, putting infants at
increased risk of suboptimal LC-PUFA intake.
• This is of particular concern when the infant is not
breastfed and/or if the lactating mother has very low
intakes of LC-PUFA's herself.
• A study estimating DHA and ARA intakes in low
income countries for children aged 6-36 months found
median intake of 48.9 mg and 64 mg/day
respectively.
• On average, infants were only receiving half of the
recommended daily intake of DHA.

41. LC-PUFA Intake and Preterm
Health Outcomes
• LC-PUFA's are preferentially transferred across
the placenta and accumulate extensively during
the third trimester in the foetal brain and retina.
• In term infants, a substantial amount of LC-PUFAs
is stored in the body e.g. in adipose tissue and
liver lipids .
• Premature infants miss this increased accretion
and have extremely small fat stores, placing them
at risk of LC-PUFA deficiency. The more
premature they are born, the higher the risk of
deficiency .

42. • Low LC-PUFA status and the decline in LC-
PUFA status after birth may be associated
with increased incidence and/or severity of
several common comorbidities associated
with prematurity:
• Chronic lung diease
• Late onset sepsis
• Necrotising enterocolitis
• Retinopathy
• Bronchopulmonary dsyplasia

43. • Many Randomised controlled trials suggest a positive link
between LC-PUFA supplementation of preterm infants and
visual and cognitive outcomes .
• Experimental and clinical trials indicate that the provision of
higher amounts of LC-PUFA are associated with better
neurological outcomes up to 2 years.
• Currently, preterm formulae universally contain about 0.2%-
0.3% DHA of total FAs (approx. 20mg/kg/d), the same amount
that breastfed preterm infants receive through breastmilk.
• The desirable LC-PUFA supply for preterm infants with a body
weight up to 1500 g is much higher than for term infants and
amounts to 55-60 mg DHA/kg body weight daily and 35-45
mg ARA/kg body weight daily.

44. THANKS FOR YOUR
ATTENTION