Expectant mothers who take fish oil supplements may reduce their child's risk for respiratory allergies, or reduce severity.
by Craig Weatherby
Rates of allergic diseases in children have increased dramatically in western countries over the past 30 years.
Allergies are often attributed to lifestyle factors, such as overly clean modern environments and poor diets, but the causes remain uncertain. Some inflammatory respiratory conditions, such as asthma, also have an inherited, genetic component.
Omega-3s may be important influences
Long-chain omega-3 fatty acids – like those from fish – are key constituents of our cell membranes and immune systems.
Omega-3s exert an anti-inflammatory influence on the immune system, and have been studied for their therapeutic or preventive potential inflammatory conditions ranging from eczema, asthma, and hay fever to rheumatoid arthritis and Crohn’s Disease.
But research results testing the preventive or therapeutic potential of omega-3s versus inflammatory conditions have been mixed, with perhaps the clearest positive impact seen in alleviating rheumatoid arthritis symptoms.
Past studies concerning asthma prevention or treatment with omega-3s have also been mixed, but have produced generally positive results.
(See “Prior studies on omega-3s and allergies in children”, at the end of this article.)
European study links higher omega-3 intake to lower asthma risk
Danish researchers traced the children born to mothers who took part in a trial conducted in 1990 (Olsen SF et al. 2008).
In the original trial, more than 500 pregnant women were split into three groups for the last 10 weeks of their pregnancy. One group was given fish-oil supplements, another got placebo (olive oil) capsules, and the third group took no supplements.
The mothers who took fish oil increased the length of their pregnancies by an average of four days and the average birth weight of their babies by about 100 grams (3.5 ounces).
The purpose of the trial was to see whether the effects of fish oil taken in very early life had any effect on the child’s risk of developing asthma as they grew up.
By the time they were 16 years old, 19 of the children had developed such severe asthma, that at some point they had to go to hospital.
But overall, the risk of developing asthma was reduced in the children whose mothers had been given fish oil supplements, compared to those whose mothers had been given olive oil supplements.
According to professor Sjurdur F. Olsen of Harvard University and Denmark's Statens Serum Institut, “There is strong evidence that the omega-3 fatty acids in fish oil may have modulating effects on the immune system. The reason fish oil might protect a fetus from developing asthma in later life could possibly also be related to its effect on increasing pregnancy duration.”
(For more on this, see “Can Omega-3s Help Prevent Premature Births?”.)
Premature children have a higher risk of developing asthma and the omega 3 fatty acids found in fish oils could both reduce the risk of pre-term birth and the likelihood of a baby later becoming asthmatic through their effect on reducing inflammation.
“It may be that the period shortly before delivery is the critical window for these effects of omega 3 fatty acids,” said Prof Olsen.
The researchers warned that because this was a relatively small trial, the results and must be confirmed by larger, controlled studies.
Prior studies on omega-3s and allergies in children
These are some of the highlights of related research over the past five years:
US study finds fish protective and fried fish sticks problematic
Three years ago, researchers at the University of Southern California in Los Angeles reported finding that the children of pregnant women with asthma who ate oily fish such as Salmon were less likely to develop asthma (Salam MT et al. 2005).
The study also found that children whose mother ate fish sticks during pregnancy were twice as likely to develop asthma, whether or not their mothers had asthma themselves.
As co-author Frank Gilliland said at the time, “Fish sticks are deep-fried, and they contain omega-6 fatty acids, which encourage inflammation of the airways” (Gilliland meant to say that the omega-6s come from the cheap vegetable oils in which fish are fried).
The study found that children whose mothers with asthma ate oily fish during pregnancy were, on average, 71 percent less likely to develop asthma. And the more oily fish a woman ate, the less likely her child was to develop asthma.
Children with non-asthmatic mothers did not benefit from having their mother eat oily fish during pregnancy.
As the authors noted, family history of asthma is a very strong risk factor for a child developing asthma, and it may be that the omega-3s in oily fish interact with the genes involved in the predisposition to develop asthma, and somehow reduces the risk.
Aussie study finds maternal fish oil supplements eases kids’ risk of allergies
Five years ago, an Australian team reported positive effects of fish oil supplementation (from 20 weeks gestation to delivery) on the offspring of in 40 pregnant women (Dunstan JA et al. 2003).
The women all had a history of hay fever or asthma, making their children at increased risk of developing allergies. Another 43 women served as a control group, and took an olive oil placebo.
The supplements resulted in significantly higher levels of omega-3 and lower levels of pro-inflammatory omega-6 fatty acids in cell membranes of babies born to mothers in the fish oil group.
Cells taken from the umbilical cord of these babies generally had weaker immune response to allergens, and at one year of age, the offspring of mothers who had taken fish oil supplements were three times less likely be sensitized to egg allergen.
And though they were more likely to develop atopic dermatitis, they were 10 times less likely to have severe disease.
Mexican study links maternal fish intake to reduced allergy in kids.
The authors of a Mexican study published last year reported that higher fish intake during pregnancy reduced the risk of eczema, dust mite allergy and allergy-related wheezing (Romieu I et al. 2007).
Spaniards link higher fish and “fruity vegetable” intake to reduced allergy rates.
Also last year, Spanish researchers reported that a diet rich in vegetables and fish can help cut asthma and allergy incidence in children (Chatzi L et al. 2007).
The Spaniards found that children who consumed more than 60 grams of omega-3 containing fish daily also suffered less childhood allergies
And Spanish children who ate more than 40 grams (1.5 ounces) of “fruity vegetables” a day – namely tomatoes, eggplant, cucumber, green beans and zucchini – were much less likely to suffer from childhood asthma.
Fruits and vegetables are rich sources of antioxidant vitamins such as vitamins C, E and carotenoids, and other antioxidants such as selenium and flavonoids, that may reduce airway inflammation by protecting cells from oxidative damage and the body’s resulting inflammatory response.
Brits fail to find strong link between fatty acids and allergies in kids
The authors of a British study published in 2004 linked higher blood levels of omega-6s to greater risk of allergies.
However, after accounting for other factors, they found it unlikely that “…fetal exposure to omega-6 and omega-3 fatty acids is an important determinant of early childhood wheezing and atopic [allergic] disease” (Newson RB et al. 2004).
The results of the new Danish study seem to tip the balance in favor of the potential for maternal omega-3 intake to prevent asthma and allergies in children, or at least or ameliorate their severity.
- Chatzi L, Torrent M, Romieu I, Garcia-Esteban R, Ferrer C, Vioque J, Kogevinas M, Sunyer J. Diet, wheeze, and atopy in school children in Menorca, Spain. Pediatr Allergy Immunol. 2007 Sep;18(6):480-5.
- Dunstan JA, Mori TA, Barden A, Beilin LJ, Taylor AL, Holt PG, Prescott SL. Fish oil supplementation in pregnancy modifies neonatal allergen-specific immune responses and clinical outcomes in infants at high risk of atopy: a randomized, controlled trial. J Allergy Clin Immunol. 2003 Dec;112(6):1178-84.
- Newson RB, Shaheen SO, Henderson AJ, Emmett PM, Sherriff A, Calder PC. Umbilical cord and maternal blood red cell fatty acids and early childhood wheezing and eczema. J Allergy Clin Immunol. 2004 Sep;114(3):531-7.
- Olsen SF, Řsterdal ML, Salvig JD, Mortensen LM, Rytter D, Secher NJ, Henriksen TB.Fish oil intake compared with olive oil intake in late pregnancy and asthma in the offspring: 16 y of registry-based follow-up from a randomized controlled trial.Am J Clin Nutr. 2008 Jul;88(1):167-75.
- Romieu I, Torrent M, Garcia-Esteban R, Ferrer C, Ribas-Fitó N, Antó JM, Sunyer J. Maternal fish intake during pregnancy and atopy and asthma in infancy. Clin Exp Allergy. 2007 Apr;37(4):518-25.
- Salam MT, Li YF, Langholz B, Gilliland FD. Maternal fish consumption during pregnancy and risk of early childhood asthma. J Asthma. 2005 Jul-Aug;42(6):513-8.