More Splash Than Analysis: News of a Recent Allergy Finding

Lise Broer
Mar 6, 2018 · 3 min read
Fish oil or snake oil? Image credit Wampole’s Preparation, public domain.

When it comes to pregnancy and the first months after birth, caution is the watchword — or it ought to be. Last week when a new report got published about maternal nutrition and childhood allergies I warned that “supplement merchants may very well leap on the potential benefits and overlook the caveats.” Guess who else overlooked the downsides? None other than the BBC.

To recap the matter, a newly published review paper finds significant reduction in the rate of childhood allergies among mothers who consume probiotics and Omega-3 supplements from fish oil. What that paper also concludes is that women should not take probiotics during the first eight months of pregnancy, that women who have a history of intestinal disorders or immune deficiencies should not consume probiotics during pregnancy or nursing at all, and that there are specific narrow windows for beneficial correlations associated with probiotics and fish oil.

The BBC report gets one thing right: this research offers a preliminary finding that points a direction for further research. It misses the rest.

The researchers looked at 19 trials of fish oil supplements taken during pregnancy involving 15,000 people, finding that the reduction in allergy risk equated to 31 fewer cases of egg allergy per 1,000 children.

They also looked at the impact of probiotic supplements taken during pregnancy and found a 22% reduction in the risk of eczema developing in children up to the age of three.

Compare that to the researchers’ own interpretation of their data.

There are two specific implications for pregnant women. First, a daily probiotic supplement such as L. rhamnosus, taken from around 36 to 38 weeks gestation through the first 3 to 6 months of lactation, may reduce risk of eczema in the child. Although probiotics are generally considered safe, their pro-inflammatory effects may have potential adverse consequences when used earlier in pregnancy, and serious adverse effects in people with intestinal disorders or immune deficiency have been documented. Second, a fish oil supplement, taken from around 20 weeks gestation through the first 3 to 4 months of lactation, may reduce risk of allergic sensitisation to egg or peanut in the child.

The BBC coverage mentions nothing about taking probiotics during lactation, which is where the bulk of the correlation actually occurs. The researchers specify a two week window for probiotics during the final month of pregnancy — a distinction completely missing from the BBC report. None of the negative cautions against taking probiotics during the first eight months of pregnancy or against taking probiotics if the woman has specific types of medical history make it into the report at all.

In other words the BBC is suggesting that pregnant women take probiotics when doing so is dangerous and not suggesting new mothers do so when it might be beneficial. It further suggests that “these findings need to be considered when guidelines for pregnant women are updated,” which can leave readers with the impression that the main reason probiotics are not yet recommended throughout pregnancy is a bureaucratic scheduling delay.

Similar oversimplification distorts the BBC reporting on fish oil: the actual finding covers the second half of pregnancy and the first several months of breastfeeding; the BBC mentions only its association with consumption during pregnancy and fails to articulate that no known benefit occurs before 20 weeks.

It turns out I was overly optimistic: a supplement vendor intent of maximizing profit has no need to overlook the cautions and hype preliminary findings. An otherwise respectable news source has already done that for them.

Lise Broer

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science-based writing about food allergies