IMPACT OF DHA ON INFECTIONS & INFLAMMATION

Docosahexaenoic acid (DHA) is a n-3 polyunsaturated fatty acid with multiple functions. The impact of DHA on development of visual and neurological functions has been demonstrated in infants and neonates and its effects have been reported in certain neurological chronic diseases and inflammatory and metabolic disorders (1).

Role of DHA on respiratory infections :

There have been recent reports of impact of DHA in decreasing incidence of respiratory infections in children upto 3 years of age (2,3). In study in USA, it was found that children who were given DHA with arachidonic acid (ARA) had significantly lower odds for developing upper respiratory infections (URI), wheezing/asthma or any allergy (2). In another study in Kansas city, USA it was found that children between 18-36 months who were given formula with DHA had higher RBC DHA and fewer adverse events and a lower incidence of respiratory illness (p = 0.024) compared to formula without DHA. Thus the authors concluded that modest increase in DHA intake in toddlers might improve respiratory health. (3). Saedisomeolia et al found that DHA reduces the release of inflammatory mediators from airway epithelial cells infected with rhinovirus (RV) (4)

Effect of DHA on inflammatory markers :

In vitro studies demonstrate DHA inhibits the expression of inflammatory markers such as pro-inflammatory cytokines, monocyte adhesion to endothelial cells (5). This may also have a protective effect on atopy and research from South Korea suggests that reduced content of n-3 PUFA in the RBC membrane could play a role in early children atopy (6). A number of studies have demonstrated that both Eicosapentaenoic acid (EPA) and DHA are bioactive and suppress antigen-specific delayed hypersensitivity reactions and mitogen-induced proliferation of T-cells, as well as modulate murine T-helper cell (Th1/Th2) balance (7). In general, the consumption of EPA and DHA are associated with lower levels of inflammatory mediators and soluble adhesion molecules.

Lopez-Alarcon et al supplemented neonates who developed sepsis after a surgical procedure with 100 mg of DHA for 14 days. They found that orogastric DHA administered in the acute phase of infection protects the nutritional status of neonates with sepsis. (8)

DHA consumption in children :

However consumption of DHA is inadequate in regular diet of children. The study from Kansas has found that toddlers in USA have low DHA intake and low red cell DHA levels (3). Dietary intakes in childhood are consistent with future eating patterns supporting adult health, such as prevention of metabolic disorders and cardiovascular disease, supporting immune function, and reproductive health (9). Data summarized by Burdge and Calder suggest that the conversion of alpha linolenic acid to DHA is less than 0.5% and that the beneficial effects of DHA occur at the level of 500 mg/day. This gap between intake and efficacy suggests that DHA is conditionally essential. (10) Because of the tendency for the average diet to be low in DHA, supplementation may be indicated. Studies show DHA from algae is a good vegetarian source of omega-3 fatty acids, bioequivalent to DHA derived from fish and safe from supplementation to all age groups, including preterm infants (11).

Conclusion :

DHA due to its down regulation of inflammatory markers has been found to be useful in respiratory infections.

References :

1.	Gil-Campos M, Dalmau Serra J, Comite de Nutricion de la Asicuacion Espanola de Pediatria. Importance of docoshexaenoic acid (DHA); Functions and recommendations for its ingestion in infants. An Pediatr (Barc). 2010 Jun 4, [Epub ahead of print].
2.	Birch EE, Khoury JC, Berseth CL, Castaneda YS, Couch JM, Bean J et al. The impact of early nutrition on incidence of allergic manifestations and common respiratory illnesses in children. J Pediatr 2010; 156: 902-906e1.
3.	Minns LM, Kerling EH, Neely MR, Sullivan DK, Wampler JL et al. Toddler formula supplemented with docosahexaenoic acid (DHA) improves DHA status and respiratory health in a randomized, double blind, controlled trial of US children less than 3 years of age. Prastaglandins Leukot Essent Fatty Acids. 2010; 82: 287-293.
4.	Saedisomeolia A, Wood LG, Garg ML, Gibson PG, Wark PA. Anti-inflammatory effects of long-chain n-3 PUFA in rhinovirus-infected cultured airway epithelial cells. Br J Nutr. 2009; 101: 533-540
5.	De Caterina R, Liao JK, Libby P. Fatty acid modulation of endothelial activation. Am J Clin Nutr. 2000; 71: 213S-223S.
6.	Hwang I, Cha A, Lee H, Yoon H, Yoon T, Cho B, Lee S et al. N-3 polyunsaturated fatty acids and atopy in Korean preschoolers. Lipids 2007; 42: 345-349.
7.	Chapkin RS, Kim W, Lupton JR, McMurray DN. Dietary docosahexaenoic and eicosapentaenoic acid: emerging mediators of inflammation. Prostaglandins Leukot Essent Fatty Acids. 2009; 81: 187-191
8.	Lopez-Alarcon M, Bernabe-Garcia M, Del Prado M, Rivera D, Ruiz G, Maldonado J, et al. Docosahexaenoic acid administered in the acute phase protects the nutritional status of septic neonates. Nutrition. 2006; 22: 731-737
9.	Koletzko B, Vauy R, Palou A, Kok F, Hornstna G, Eilander A et al. Dietary intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in children – a worshop report. Br J Nutr. 2010; 103: 923-928.
10.	Burdge GC, Calder PC. Dietary alpha-linolenic acid and health-related outcomes: a metabolic perspective. Nutr Res Rev. 2006: 26–52.
11.	Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr. 2003; 78: 640S-646S.