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What are Long Chain Polyunsaturated Fatty Acids?

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Posted on: Jul 01, 2013     Publication: Small Talk Summer 2013 print page

What are Long Chain Polyunsaturated Fatty Acids?

Kate Maslin, Allergy Research Dietitian, The David Hide Asthma and Allergy Research Centre, Isle of Wight
Dr. Carina Venter PhD RD, Allergy Specialist Dietitian, The David Hide Asthma and Allergy Research Centre, Isle of Wight. NIHR Post Doc Research Fellow, University of Portsmouth

Long Chain Polyunsaturated fatty acids (LCPs) are derived from two main polyunsaturated fatty acids; α – linolenic acid (ALA) and linoleic acid.

ALA, found in plant based foods (e.g. flaxseed and walnut oil), is the parent n-3 fatty acid, from which the LCPs Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) can be synthesised through a biochemical pathway (see figure 1). The conversion rate from ALA to EPA and DHA is very inefficient in humans. The direct consumption of EPA and DHA containing foods (i.e. oily fish and fish oils) is therefore recommended (Plourde & Cunnane, 2007).

Figure 1: Synthesis of LCPs (Adapted from Guesnet & Alessandri, 2011)

Arachidonic Acid (ARA) is the principal n-6 LCP. n-6 fatty acids are typically derived from sunflower, soybean and corn oils and it is suggested that there is an over consumption of these fatty acids in Western diets (Simopoulos, 1999).

What do LCPs do?

Both n-3 and n-6 fatty acids are found in significant amounts in the brain and visual tissues. DHA particularly, is a major component of the phospholipid structure of the cell membrane wall in the nervous system and retina. LCPs also play an important role in inflammatory and immune responses, through the production of eicosanoids. Eicosanoids derived from n-3 fatty acids are thought to be anti-inflammatory, whereas eicosanoids derived from n-6 fatty acids are mostly thought to be proinflammatory (Calder, 2012). As n-3 and n-6 fatty acids compete with each other for common enzymes, the correct ratio between them is important for health.

The benefits of LCPs to infant health

There is an extensive pool of research papers on the potential beneficial effects of these dietary fats in infants and several systematic reviews have been undertaken (Riediger et al, 2009; Kremmyda, 2011). Infants have a limited ability to synthesise LCPs themselves (Uauy et al, 2000). However, infants undergo a rapid period of neurodevelopment in utero and during the first two years of life. It is therefore critical that LCPs are available to the foetus via the maternal diet during pregnancy and following birth to the infant through breastfeeding or supplemented infant formula. During this time, it is crucial that sufficient amounts of n-3 and n-6 are accrued in the brain (Guesnet & Alessandri, 2011; Hoffman et al, 2009). It has been shown that LCPs are important for infant visual and cognitive development, with most benefits attributable to DHA (Riediger et al, 2009). It is thought that the positive effects may extend from infancy, up to 5 years of age (Agostini, 2008).

As a result of this, the World Perinatal Association in conjunction with the Early Nutrition Academy and Child Health Foundation, reviewed the available research and published guidelines in 2008, concluding that both DHA and ARA should be added to infant formula in order to provide formula-fed infants these nutrients at a comparable rate to breastfed infants (Koletzko et al, 2008).

Benefits of LCPs within a hypoallergenic formula

The ability of n-3 fatty acids to downregulate aspects of inflammation suggest that they may be important in influencing the development and severity of inflammatory diseases (Calder, 2012), such as allergy and asthma. In fact, it has been hypothesised that the increases in asthma, eczema and allergic rhinitis seen in the developed world may be attributable to an increase in consumption of n-6 and decrease in consumption of n-3 LCPs (Black & Sharpe, 1997). Five epidemiological studies have concluded that maternal fish intake during pregnancy has a protective effect on atopic outcomes in their infants and it is therefore postulated that n-3 LCP supplementation in infancy may decrease the risk of developing some manifestations of allergic disease (Kremmyda et al, 2011). A RCT study of 145 mother-infant pairs has demonstrated a significant relationship between higher n-3 PUFA levels in infant phospholipids and a lower frequency and less severity of allergic disease during the first 2 years of life (Furuhjelm et al, 2011).

Summary of Consenus Recommendations from the World Association of Perinatal Medicine (2008)

• The authors emphasize the importance of a balanced diet for breastfeeding women, including a regular supply of DHA.
• If breast milk is not available to the baby, current evidence supports the addition of DHA and ARA to infant formula
• The DHA added should make between 0.2% and 0.5% of fatty acids [noting that 0.2% is the minimum level necessary to see functional developmental benefits]
• Infant formula should be supplemented with ARA in amounts at least equal to the amount of DHA
• Dietary supply of DHA and ARA should continue after the first six months of life, but currently there is insufficient information to recommend exact amounts

Optimal ratio of LCPs in infant formula

Although it is not possible to say with certainty what specific LCPs or levels of LCPs provide optimal effects on respiratory health (Hageman et al, 2012), in infants at high risk of atopy, relatively high breast milk n3: n6 fatty acid ratios may be protective against the development of allergic symptoms (Wijga et al, 2006).

Breastmilk, on which infant formula is based, is known to have variable levels of LCPs, dependent on the mother’s diet. A meta-analysis of studies of levels of DHA and ARA worldwide indicated mature breast milk had ~0.32% DHA and ~0.47% ARA (Brenna et al, 2007). However it is also widely acknowledged that our diets have become unbalanced towards excess consumption of n–6 LCPs and that we should aim for an intake with a ratio of 1-2: 1 (Simopolous, 1999). EU regulation on infant formulae states there is insufficient evidence to set an obligatory minimum level of LCPUFA, however a statement relating to the presence of DHA in a formula should only be made if the content of DHA is not less than 0.2% of the total fatty acids. Furthermore, arachidonic acid should not contribute more than 1% of total fatty acids (European Commission, 2003).

Conclusion

In summary, LCPs, particularly DHA, play an important anti- inflammatory role, which is likely to be of significance in childhood allergy, in addition to the proven positive effects on visual and cognitive function. Inclusion of the optimal ratio of LCPs in a hypoallergenic infant formula may reduce the severity of allergic disease symptoms.

Refrences:
Agostini, C. J Ped Gastroenterol Nutr 2008; 47: 41-44.
Black PN, Sharpe S. Eur Resp J 1997; 10:6-12.
Brenna JT et al. Am J Clin Nutr 2007;85:1457-1464.
Calder PC 2012 Br J Pharmacol (Epub ahead of print)
EC Health & Consumer Protection Directorate. Report: SCF/CS/NUT/IF/65, 2003. Brussels.
Furuhjelm C et al. Ped Allerg Immunol 2011; 22: 505-514.
Guesnet P, Alessandri J. Biochimie, 2011; 93: 7-12.
Hageman JH et al. Curr Allergy Asthma Rep 2012; 12: 564-573.
Hoffman DR et al. Prostaglandins Leukot Essent Fatty Acids. 2009; 81(2-3):151-8
Koletzko B et al. Journal of Perinatal Medicine 2008; 36(1): 5-14.
Kremmyda LS et al. Clin Rev Allerg Immunol, 2011; 4(1): 36-66.
Plourde M, Cunnane SC. Appl Physiol Nutr Metab 2007; 32: 619-634.
Riediger ND et al. J Am Diet Assoc. 2009; 109(4):668-79
Simopoulos AP. Am J Clin Nutr 1999; 70(suppl): 560S-569S.
Uauy R et al. Ped Res 2000; 47(1):127-35.
Wijga AH et al. J Allerg Clin Immunol 2006; 117: 440-447.

Tags: paediatrics



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