Atopy risk in infants and children in relation to early exposure to fish, oily fish, or long-chain omega-3 fatty acids: a systematic review

Maternal plasma phosphatidylcholine fatty acids and atopy and wheeze in the offspring at age of 6 years

Variation in exposure to polyunsaturated fatty acids (PUFAs) might influence the development of atopy, asthma, and wheeze. This study aimed to determine whether differences in PUFA concentrations in maternal plasma phosphatidylcholine are associated with the risk of childhood wheeze or atopy. For 865 term-born children, we measured phosphatidylcholine fatty acid composition in maternal plasma collected at 34 weeks' gestation. Wheezing was classified using questionnaires at 6, 12, 24, and 36 months and 6 years. At age of 6 years, the children underwent skin prick testing, fractional exhaled nitric oxide (FENO) measurement, and spirometry. Maternal n-6 fatty acids and the ratio of n-3 to n-6 fatty acids were not associated with childhood wheeze. However, higher maternal eicosapentaenoic acid, docosahexaenoic acid, and total n-3 fatty acids were associated with reduced risk of non-atopic persistent/late wheeze (RR 0.57, 0.67 and 0.69, resp. P = 0.01, 0.015, and 0.021, resp.). Maternal arachidonic acid was positively associated with FENO (P = 0.024). A higher ratio of linoleic acid to its unsaturated metabolic products was associated with reduced risk of skin sensitisation (RR 0.82, P = 0.013). These associations provide some support for the hypothesis that variation in exposure to n-6 and n-3 fatty acids during pregnancy influences the risk of childhood wheeze and atopy.

Fatty acids in breast milk associated with asthma-like symptoms and atopy in infancy: a longitudinal study

OBJECTIVE

The relationship between fatty acids (FAs) in breast milk and the risk of childhood allergies is controversial. We prospectively investigated the relationship between FAs in colostrum and breast milk and asthma-like symptoms (AS) and atopy in infancy.

METHODS

Pregnant women were recruited in Columbia and Charleston, South Carolina. Colostrum and mature milk samples were collected. The concentrations of n-3 FAs (eicosapentaenoic acid, α-linolenic acid, docosapentaenoic acid, and docosahexaenoic acid) and n-6 FAs (linoleic acid, arachidonic acid, and eicosadienoic acid) were determined by gas chromatography. AS were ascertained at 6 and 12 months of age and atopy (skin prick test) at 12 months. FAs were dichotomized (high vs. median and low). Generalized estimating equations were used to determine the effect of FAs on repeated AS, compensating for intra-individual correlations and adjusting for confounders. Log-linear regression was used to analyze atopy.

RESULTS

FAs were analyzed in 24 colostrum and 78 breast milk samples. High levels of total n-6 (lipid based) FAs in breast milk were associated with an increased risk of AS in infants (risk ratio (RR) = 2.91; 95% confidence interval (CI): 1.37, 6.18), even after controlling for total n-3 FAs (RR = 2.07, 95% CI: 1.12, 3.85). High levels of total n-3 FAs controlling for n-6 FAs decreased the risk of atopy at the age of 12 months.

CONCLUSIONS

High levels of total n-6 polyunsaturated fatty acids (PUFAs) in breast milk are associated with an increased risk for AS, whereas high levels of total n-3 PUFAs decreased the risk of atopy. These data suggest that the effects of n-3 and n-6 PUFAs on allergic disorders should be further explored.

Role of dietary long-chain polyunsaturated fatty acids in infant allergies and respiratory diseases

Maternal nutrition has critical effects on the developing structures and functions of the fetus. Malnutrition during pregnancy can result in low birth weight and small for gestational age babies, increase risk for infection, and impact the immune system. Long-chain polyunsaturated fatty acids (PUFAs) have been reported to have immunomodulatory effects. Decreased consumption of omega-6 PUFAs, in favor of more anti-inflammatory omega-3 PUFAs in modern diets, has demonstrated the potential protective role of omega-3 PUFAs in allergic and respiratory diseases. In this paper, we examine the role of PUFAs consumption during pregnancy and early childhood and its influence on allergy and respiratory diseases. PUFAs act via several mechanisms to modulate immune function. Omega-3 PUFAs may alter the T helper (Th) cell balance by inhibiting cytokine production which in turn inhibits immunoglobulin E synthesis and Th type 2 cell differentiation. PUFAs may further modify cellular membrane, induce eicosanoid metabolism, and alter gene expression. These studies indicate the benefits of omega-3 PUFAs supplementation. Nevertheless, further investigations are warranted to assess the long-term effects of omega-3 PUFAs in preventing other immune-mediated diseases, as well as its effects on the later immunodefense and health status during early growth and development.

Fermented fish oil suppresses T helper 1/2 cell response in a mouse model of atopic dermatitis via generation of CD4+CD25+Foxp3+ T cells

Background

Allergic skin inflammation such as atopic dermatitis (AD), which is characterized by pruritus and inflammation, is regulated partly through the activity of regulatory T cells (Tregs). Tregs play key roles in the immune response by preventing or suppressing the differentiation, proliferation and function of various immune cells, including CD4⁺ T cells. Recent studies report that fermentation has a tremendous capacity to transform chemical structures or create new substances, and the omega-3 polyunsaturated fatty acids (n-3 PUFAs) in fish oil can reduce inflammation in allergic patients. The beneficial effects of natural fish oil (NFO) have been described in many diseases, but the mechanism by which fermented fish oil (FFO) modulates the immune system and the allergic response is poorly understood. In this study, we produced FFO and tested its ability to suppress the allergic inflammatory response and to activate CD4⁺CD25⁺Foxp3⁺ Tregs.

Results

The ability of FFO and NFO to modulate the immune system was investigated using a mouse model of AD. Administration of FFO or NFO in the drinking water alleviated the allergic inflammation in the skin, and FFO was more effective than NFO. FFO treatment did increase the expression of the immune-suppressive cytokines TGF-β and IL-10. In addition, ingestion of FFO increased Foxp3 expression and the number of CD4⁺CD25⁺Foxp3⁺ Tregs compared with NFO.

Conclusions

These results suggest that the anti-allergic effect of FFO is associated with enrichment of CD4⁺CD25⁺ Foxp3⁺ T cells at the inflamed sites and that FFO may be effective in treating the allergic symptoms of AD.

Salmon consumption during pregnancy alters fatty acid composition and secretory IgA concentration in human breast milk

Fish oil supplementation during pregnancy alters breast milk composition, but there is little information about the impact of oily fish consumption. We determined whether increased salmon consumption during pregnancy alters breast milk fatty acid composition and immune factors. Women (n = 123) who rarely ate oily fish were randomly assigned to consume their habitual diet or to consume 2 portions of farmed salmon per week from 20 wk of pregnancy until delivery. The salmon provided 3.45 g long-chain (LC) (n-3) PUFA/wk. Breast milk fatty acid composition and immune factors [soluble CD14, transforming growth factor-β (TGFβ)1, TGFβ2, and secretory IgA] were analyzed at 1, 5, 14, and 28 d postpartum (PP). Breast milk from the salmon group had higher proportions of EPA (80%), docosapentaenoic acid (30%), and DHA (90%) on d 5 PP compared with controls (P < 0.01). The LC (n-6) PUFA:LC (n-3) PUFA ratio was lower for the salmon group on all days of PP sampling (P ≤ 0.004), although individual (n-6) PUFA proportions, including arachidonic acid, did not differ. All breast milk immune factors decreased between d 1 and 28 PP (P < 0.001). Breast milk secretory IgA (sIgA) was lower in the salmon group (d 1-28 PP; P = 0.006). Salmon consumption during pregnancy, at the current recommended intakes, increases the LC (n-3) PUFA concentration of breast milk in early lactation, thus improving the supply of these important fatty acids to the breast-fed neonate. The consequence of the lower breast milk concentration of sIgA in the salmon group is not clear.

Does consumption of two portions of salmon per week enhance the antioxidant defense system in pregnant women?

Salmon is a rich source of marine n-3 fatty acids, which may increase oxidative stress and, in turn, could affect the antioxidant defense system in blood plasma and erythrocytes of pregnant women. The Salmon in Pregnancy Study provided two meals of salmon per week to pregnant women from week 20 of gestation; the control group maintained their habitual diet low in oily fish. Higher selenium and retinol plasma concentrations were observed after dietary salmon supplementation. Besides, a concomitant increase in selenium and glutathione concentration as well as glutathione peroxidase and reductase activities were detected as pregnancy progressed. However, tocopherols, retinol, β-carotene, and coenzyme Q(10) decreased in late pregnancy. Collectively, our findings lead to the hypothesis that increased farmed salmon intake may increase antioxidant defenses during pregnancy. Clinical trials identifier NCT00801502.

Omega-3 fatty acids and pregnancy: current implications for practice

PURPOSE OF REVIEW

We conducted this review to evaluate the evidence for maternal supplementation with omega-3 fatty acids during pregnancy for the prevention or treatment of common complications of pregnancy including preterm birth, pregnancy-induced hypertension and preeclampsia, as well as perinatal depression. We also evaluated the evidence supporting maternal omega-3 fatty acid supplementation to optimize infant neurocognitive development and for primary prevention of allergic diseases in childhood.

RECENT FINDINGS

Omega-3 fatty acids through diet or dietary supplementation may reduce the risk for early preterm birth. Preliminary findings from small randomized controlled trials suggest that maternal omega-3 fatty acid supplementation during pregnancy may reduce the risk for allergic disease in childhood, but this observation requires confirmation by large appropriately powered randomized controlled trials. More research is needed before routine maternal supplementation for this indication can be recommended.

SUMMARY

Although it is biologically plausible that maternal omega-3 fatty acid supplementation might prevent a number of pregnancy complications and optimize child health and development, indications for supplementation other than prevention of preterm births are currently investigational.

Fatty acids as biocompounds: their role in human metabolism, health and disease: a review. part 2: fatty acid physiological roles and applications in human health and disease

BACKGROUND

This is the second of two review parts aiming at describing the major physiological roles of fatty acids, as well as their applications in specific conditions related to human health.

RESULTS

The review included the current literature published in Pubmed up to March 2011. In humans, fatty acids are a principle energy substrate and structural components of cell membranes (phospholipids) and second messengers. Fatty acids are also ligands of nuclear receptors affecting gene expression. Longer-chain (LC) polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid are precursors of lipid mediators such as eicosanoids (prostaglandins, leukotrienes, thromboxanes), resolvins and neuroprotectins. Lipid mediators produced by EPA and DHA (LC n-3 PUFA; mainly found in oily fish) are considered as inflammation-resolving, and thus, fish oil has been characterised as antiinflammatory. Recommendations for EPA plus DHA intake from oily fish vary between 250-450 mg/day. Dietary reference values for fat vary between nutrition bodies, but mainly agree on a low total and saturated fat intake. The existing literature supports the protective effects of LC n-3 PUFA (as opposed to n-6 PUFA and saturated fat) in maternal and offspring health, cardiovascular health, insulin sensitivity, the metabolic syndrome, cancer, critically ill patients, and immune system disorders.

CONCLUSION

Fatty acids are involved in multiple pathways and play a major role in health. Further investigation and a nutrigenomics approach to the effects of these biocompounds on health and disease development are imperative and highlight the importance of environmental modifications on disease outcome.

Increased intake of oily fish in pregnancy: effects on neonatal immune responses and on clinical outcomes in infants at 6 mo

BACKGROUND

Long-chain n-3 PUFAs found in oily fish may have a role in lowering the risk of allergic disease.

OBJECTIVE

The objective was to assess whether an increased intake of oily fish in pregnancy modifies neonatal immune responses and early markers of atopy.

DESIGN

Women (n = 123) were randomly assigned to continue their habitual diet, which was low in oily fish, or to consume 2 portions of salmon per week (providing 3.45 g EPA plus DHA) from 20 wk gestation until delivery. In umbilical cord blood samples (n = 101), we measured n-3 fatty acids, IgE concentrations, and immunologic responses. Infants were clinically evaluated at age 6 mo (n = 86).

RESULTS

Cord blood mononuclear cell (CBMC) production of interleukin (IL)-2, IL-4, IL-5, IL-10, and tumor necrosis factor-α in response to phytohemagglutinin (PHA) and of IL-2 in response to Dermatophagoides pteronyssinus allergen 1 (Derp1) was lower in the salmon group (all P ≤ 0.03). In the subgroup of CBMCs in which an allergic phenotype was confirmed in the mother or father, IL-10 production in response to Toll-like receptor 2, 3, and 4 agonists, ovalbumin, salmon parvalbumin, or Derp1 and prostaglandin E(2) production in response to lipopolysaccharide or PHA was lower in the salmon group (all P ≤ 0.045). Total IgE at birth and total IgE, incidence and severity of atopic dermatitis, and skin-prick-test positivity at 6 mo of age were not different between the 2 groups.

CONCLUSION

Oily fish intervention in pregnancy modifies neonatal immune responses but may not affect markers of infant atopy assessed at 6 mo of age. This trial is registered at clinicaltrials.gov as NCT00801502.

Enhanced prostaglandin F2α formation in human pregnancy and the effect of increased oily fish intake: results from the Salmon in Pregnancy Study

Oily fish intake during pregnancy may reduce the risk of allergic diseases in infancy possibly by shifts in the fatty acid balance and subsequent altered prostaglandin (PG) formation. This intervention is the first study to evaluate if increased oily fish intake affects in vivo PGF(2α) formation during pregnancy. British pregnant women were randomised to two portions of farmed salmon weekly (n=47), or maintenance of their normal diet low in fish (n=41), from pregnancy week 20 until parturition. The concentrations of eicosapentaenoic and docosahexaenoic acids in plasma phosphatidylcholine (PC) were higher and the concentration of arachidonic acid in plasma PC was lower in the salmon group than the control group at weeks 34 and 38 of pregnancy. PGF(2α) formation was evaluated by urinary measurement of 15-keto-dihydro-PGF(2α), a major PGF(2α) metabolite, at 20, 34 and 38 weeks. In both the salmon and control groups urinary 15-keto-dihydro-PGF(2α) concentrations increased significantly during pregnancy, which may be of physiological importance. Oily fish intervention altered fatty acid concentrations but did not affect urinary 15-keto-dihydro-PGF(2α) concentrations in pregnant women.

Does increased intake of salmon increase markers of oxidative stress in pregnant women? The salmon in pregnancy study

The Salmon in Pregnancy Study provided two meals of salmon per week to pregnant women from week 20 of gestation; the control group maintained their habitual diet low in oily fish. Salmon is a rich source of marine n-3 fatty acids. Since marine n-3 fatty acids may increase oxidative stress, we investigated whether increased salmon consumption could affect markers of oxidative stress in mid and late pregnancy. Urinary 8-iso-prostaglandin F(2α), urinary 8-hydroxy-2'-deoxyguanosine, and plasma lipid peroxide concentrations did not change from week 20 to 38 of pregnancy and were not altered by increased consumption of salmon. Thus, increased intake of salmon during pregnancy does not increase oxidative stress, as judged by the markers of oxidative damage to lipids and DNA measured herein.

Novel challenges for the allergist

The last years have witnessed novel findings with exciting developments in the field of allergy-related diseases including asthma, bronchial hyperresponsiveness, eczema, and atopy that have enormously increased over the past few years. This issue of the Reviews is timely dedicated to comprehensive articles discussing the current trends in the study of these conditions. In particular, the impact of new data in genomics, environmental factors through epigenetics and proteomics will be reviewed and critically discussed.

Early protective and risk factors for allergic rhinitis at age 4½ yr

Allergic heredity plays a major role in the development of allergic rhinitis. In addition the introduction of food may influence the risk of subsequent allergic disease. The aim of this study was to analyse early risk factors and protective factors for allergic rhinitis at preschool age. Data were obtained from a prospective, longitudinal study of a cohort of children born in the region of western Sweden in 2003 and 8,176 families (50% of the birth cohort) were randomly selected. The parents answered questionnaires at 6 and 12 months and at 4½ yr of age. The response rate at 4½ yr was 4,496, i.e. 83% of the 5,398 questionnaires distributed at 4½ yr. At 4½ yr of age, 5.5% reported symptoms of allergic rhinitis during the last year. In the multivariate analysis, independent risk factors for allergic rhinitis were: allergic sensitisation to food allergens at 4½ yr (OR 10.21; 95% confidence interval 4.22-24.73), recurrent wheeze at 4½ yr (3.33; 1.56-7.10), doctor-diagnosed eczema at 4½ yr (2.72; 1.62-4.55), parental rhinitis (2.21; 1.39-3.53), eczema first year (1.97; 1.19-3.26) and male gender (1.82; 1.13-2.94). The risk was reduced with fish introduction before 9 months (0.49; 0.29-0.82). In conclusion, we found that previous and present allergic disease, heredity and male gender increased the risk of allergic rhinitis at 4½ yr of age. The introduction of fish before the age of 9 months reduced the risk.

Use of a common food frequency questionnaire (FFQ) to assess dietary patterns and their relation to allergy and asthma in Europe: pilot study of the GA2LEN FFQ

BACKGROUND/OBJECTIVES

Comparable international data on food and nutrient intake is often hindered by the lack of a common instrument to assess food intake. The objective of this study was within the Global Allergy and Asthma European Network of Excellence (GA(2)LEN), we developed and piloted a food frequency questionnaire (FFQ) to assess its validity in Europe.

SUBJECTS/METHODS

Five countries participating in GA(2)LEN took part in the pilot study. A total of 200 adults aged 31-75 years were invited to complete a FFQ in two occasions and to give a blood sample. The intra-class correlation coefficient (ICC) was used to assess repeatability of the FFQ. Plasma phospholipid fatty acids (FAs) were analysed by gas chromatography. Pearson correlation was used to analyse the correlation between estimated dietary FA intake and plasma phospholipid FA levels.

RESULTS

A total of 177 participants (89%) had complete data on FFQ(1) and plasma phospholipid FAs. In all, 152 participants (76%) completed both FFQs. ICCs between macronutrients ranged from 0.70 (saturated FAs) to 0.78 (proteins) and between 0.70 (retinol) and 0.81 (vitamin D) for micronutrients. Dietary n-3 FAs showed a good correlation with total plasma phospholipid n-3 FAs and with docosahexaenoic acid in the whole sample (0.40) and in individual countries. Poor correlations were observed for other FAs.

CONCLUSIONS

The GA(2)LEN FFQ is an appropriate tool to estimate dietary intake for a range of nutrients across Europe regardless of cultural and linguistic differences. The FFQ seems to be useful to estimate the intake of n-3 FAs but not other FAs.

Essential fats for future health. Proceedings of the 9th Unilever Nutrition Symposium, 26-27 May 2010

The 9th Unilever Nutrition Symposium entitled 'Essential fats for future health', held on 26-27 May 2010, aimed to review the dietary recommendations for essential fatty acids (EFA); discuss the scientific evidence for the roles of EFA in cognition, immune function and cardiovascular health; and to identify opportunities for joint efforts by industry, academia, governmental and non-governmental organizations to effectively improve health behaviour. This paper summarizes the main conclusions of the presentations given at the symposium. Linoleic acid (LA) and α-linolenic acid (ALA) are EFA that cannot by synthesized by the human body. Docosahexaenoic acid (DHA) is considered as conditionally essential because of its limited formation from ALA in the human body and its critical role in early normal retinal and brain development and, jointly with eicosapentaenoic acid (EPA), in prevention of cardiovascular disease (CVD). Some evidence for possible beneficial roles of n-3 fatty acids for immune function and adult cognitive function is emerging. A higher consumption of polyunsaturated fatty acids (PUFA; >10%E), including LA, ALA and at least 250-500 mg per day of EPA+DHA, is recommended for prevention of coronary heart disease (CHD). Two dietary interventions suggest that EFA may affect CVD risk factors in children similarly as in adults. To ensure an adequate EFA intake of the population, including children, public health authorities should develop clear messages based on current science; ensure availability of healthy, palatable foods; and collaborate with scientists, the food industry, schools, hospitals, health-care providers and communities to encourage consumers to make healthy choices.

Omega-3 fatty acids and inflammatory processes

Long chain fatty acids influence inflammation through a variety of mechanisms; many of these are mediated by, or at least associated with, changes in fatty acid composition of cell membranes. Changes in these compositions can modify membrane fluidity, cell signaling leading to altered gene expression, and the pattern of lipid mediator production. Cell involved in the inflammatory response are typically rich in the n-6 fatty acid arachidonic acid, but the contents of arachidonic acid and of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can be altered through oral administration of EPA and DHA. Eicosanoids produced from arachidonic acid have roles in inflammation. EPA also gives rise to eicosanoids and these often have differing properties from those of arachidonic acid-derived eicosanoids. EPA and DHA give rise to newly discovered resolvins which are anti-inflammatory and inflammation resolving. Increased membrane content of EPA and DHA (and decreased arachidonic acid content) results in a changed pattern of production of eicosanoids and resolvins. Changing the fatty acid composition of cells involved in the inflammatory response also affects production of peptide mediators of inflammation (adhesion molecules, cytokines etc.). Thus, the fatty acid composition of cells involved in the inflammatory response influences their function; the contents of arachidonic acid, EPA and DHA appear to be especially important. The anti-inflammatory effects of marine n-3 PUFAs suggest that they may be useful as therapeutic agents in disorders with an inflammatory component.