Swedish study finds that higher maternal omega-3 intake reduces infants' allergy risks
by Craig Weatherby
The human immune system uses the omega-3 and omega-6 fatty acids in cell membranes to make messenger chemicals called eicosanoids.
Eicosanoids, which were made famous by Barry Sears' Zone diet books, give orders to immune cells: orders that can start inflammation, control how fiery it will be, and end it.
The omega-6 fatty acids in which American diets are overloaded are used to make eicosanoids that prompt inflammation, while the eicosanoids made from omega-3s are either moderately inflammatory or anti-inflammatory.
And recent studies revealed a novel group of immune-system mediators made from omega-3s (resolvins, docosatrienes, and neuroprotectins), which exert independent anti-inflammatory effects.
In short, omega-3s tend to moderate inflammation in the body, while omega-6s tend to promote and extend inflammation.
What does this have to do with allergies?
Allergies are inappropriate, inflammatory immune responses to normal environmental and food chemicals. And researchers presume that the drop in omega-3 consumption in Western societies over the past century could be a food-related factor promoting allergies.
Yet, the results of clinical trials in which adults with established allergies or bronchial asthma took omega-3-rich fish oil have generally been disappointing.
However, the immature immune systems of fetuses and infants are highly influenced by environmental conditions, particularly just before and after birth (Blümer N, Renz H 2007).
There is some evidence that when fetuses absorb abundant amounts of omega-3s, this exposure affects immune cells postively, making them less likely to overreact to normal environmental and food factors.
As Australian researchers wrote in 2005, “…there is accumulating evidence that dietary [omega-3s] may have greater effects before allergic responses are established. Supplementation of the maternal diet in pregnancy with [omega-3s] may provide a non-invasive intervention with significant potential to prevent the development of allergic and possibly other immune-mediated diseases” (Dunstan JA, Prescott SL 2005).
Animal experiments strongly suggest a role of maternal omega-3 intake on allergic immune responses in their offspring, and the effects of maternal fish oil intake has been studied in a small number of clinical trials, with some positive effects on development of specific allergies.
Swedish study shows anti-allergy effects
Back in 2005, researchers at Linköping University in Sweden recruited 145 pregnant mothers from families with a history of developing allergy and asthma (SRC 2007).
They were divided into two groups: one receiving fish oil capsules and the other taking placebo capsules (soy oil).
From the 25th week of pregnancy through the third month of nursing, they were asked to take nine capsules of oil every day.
The study was double blind: that is, neither the participants nor the researchers knew who had received which pill.
At the end of the first year after their children’s birth, the infants whose mothers had taken fish oil during pregnancy and breastfeeding displayed considerably fewer allergic reactions than children whose mothers took the soy oil placebo.
The children of mothers in the fish oil group also had fewer than half as many reactions to eggs as the placebo group did.
This was a key finding, because allergic reactions to eggs early in life are strongly correlated with the later development of allergic disorders like eczema and asthma.
An immunological study of the mothers' blood supports the idea that the difference truly was due to the effects of the omega-3 fats in the fish oil.
The women who were given fish oil had less of an inflammatory eicosanoid called prostaglandin E2 in their blood. Prostaglandin E2 triggers allergic immune responses, and its production in the body is depressed when the concentration of omega-3 in cell membranes (a direct effect of higher omega-3 intake) increases.
As lead author Malin Fagerås Böttcher said, “We have been able to show that omega-3 influences the mother's immunological profile in a less inflammatory direction. Theoretically this can also affect the child's immune system, which is supported by the results of the scratch-tests.”
In the fall of 2008, the children will receive an immunological examination and an eczema check-up, and the researchers hope to monitor these children as they grow older to see if they develop airway allergies.
- Blümer N, Renz H. Consumption of omega3-fatty acids during perinatal life: role in immuno-modulation and allergy prevention. J Perinat Med. 2007;35 Suppl 1:S12-8. Review.
- de Luis DA, León R, Izaola O. [Influence of omega 3 fatty acid dietary intake on asthma] Rev Clin Esp. 2007 Jan;207(1):24-5. Review. Spanish.
- Dunstan JA, Prescott SL. Does fish oil supplementation in pregnancy reduce the risk of allergic disease in infants? Curr Opin Allergy Clin Immunol. 2005 Jun;5(3):215-21. Review.
- The Swedish Research Council (SRC). October 12, 2007. Accessed online December 10, 2007 at http://idw-online.de/pages/de/news229986