A Danish study’s results suggests pregnant women that take a fish oil supplement during the final 3 months of pregnancy may reduce their baby’s risk of developing asthma or persistent wheezing.
The study involved 736 pregnant women, in their third trimester. Half the women took a placebo containing olive oil and the other group was given 2.4 grams of fish oil. The women took the supplements until one week after birth.
Among children whose mothers took fish-oil capsules, 16.9 percent had asthma by age 3, compared with 23.7 percent whose mothers were given placebos. The difference, nearly 7 percentage points, translates to a risk reduction of about 31 percent.
In the study, the researchers noted that they are not ready to recommend that pregnant women routinely take fish oil. Although the results of the study were positive, several experts have noted that more research needs to be done before higher doses of fish oil supplements are recommended over eating more fish.
Researchers found no adverse effects in the mothers or babies, the doses were high, 2.4 grams per day is 15 to 20 times what most Americans consume from foods.
One in five young children are affected by asthma and wheezing disorders. In recent decades, the rate has more than doubled in Western countries. Previous research has shown that those conditions are more prevalent among babies whose mothers have low levels of fish oil in their bodies. The new large-scale test, reported in The New England Journal of Medicine, is the first to see if supplements can actually lower the risk.
Before doctors can make any recommendations, the study should be replicated, and fish oil should be tested earlier in pregnancy and at different doses, Dr. Hans Bisgaard, the leading author of the study, said in an email to the New York Times. He is a professor of pediatrics at the University of Copenhagen and the head of research at the Copenhagen Prospective Studies on Asthma in Childhood, an independent research unit.
Dr. Bisgaard said it was not possible to tell from the study whether pregnant women could benefit from simply eating more fish. Pregnant women are generally advised to limit their consumption of certain types of fish like swordfish and tuna because they contain mercury. But many other types are considered safe, especially smaller fish like sardines that are not at the top of the food chain and therefore not likely to accumulate mercury and other contaminants from eating other fish.
“It is possible that a lower dose would have sufficed," the Bisgaard team said.
The supplements didn't seem to affect the odds of a baby or toddler developing the skin condition eczema, or an allergy such as a reaction to milk or egg products, or a severe asthma attack.
An editorial in the same journal by an expert who was not part of the study praised the research, saying it was well designed and carefully performed. The author of that editorial, Dr. Christopher E. Ramsden, from the National Institutes of Health, said the findings would help doctors develop a “precision medicine” approach in which fish-oil treatment could be tailored to women who are most likely to benefit.
If the findings are confirmed in other populations, doctors could test to see who would mostly likely benefit from fish oil supplements. "The health care system is currently not geared for such," Bisgaard said. "But clearly this would be the future."
If you are considering taking fish oil supplements during pregnancy, be sure and check with your OB/GYN for a recommended dose.
All fish oils are not the same. Some brands of fish oil are of higher quality than others. A reputable fish oil manufacturer should be able to provide documentation of third-party lab results that show the purity levels of their fish oil, down to the particles per trillion level. Also, if the supplements smell or taste fishy, they shouldn’t. High quality fish oil supplements don’t. Avoid fish oils that have really strong or artificial flavors added to them because they are most likely trying to hide the fishy flavor of rancid oil.