What is already known on this topic
Prenatal life is considered a critical window for the development of asthma and other long-term inflammatory conditions. Both the gut bacterial composition of newborns and specific microbes in infants’ airways have been associated with increased disease risk later in life, and taking high doses of vitamin D during pregnancy seems to protect newborns against asthma.
What this research adds
By analyzing microbiota samples from nearly 700 pregnant women and their children, researchers found that taking daily doses of vitamin D and omega-3 fatty acids during pregnancy affects the newborns’ airway microbiota, but not their gut microbiota.
The findings suggest that taking vitamin D and omega-3 fatty acids during pregnancy can change the infant airway microbiota, but these microbes appear to be a minor mediator of the protective effect of the two dietary interventions on risk of asthma.
Prenatal life is considered a critical window for the development of asthma and other long-term inflammatory conditions. Both the gut bacterial composition of newborns and specific microbes in infants’ airways have been associated with increased disease risk later in life, and taking high doses of vitamin D during pregnancy seems to protect newborns against asthma. A new study found that taking vitamin D and omega-3 fatty acids during pregnancy can change the newborns’ airway microbiota.
The findings, published in Nature Communications, suggest that the beneficial effects of dietary interventions during pregnancy are mediated by different factors, including the infant airway microbiota, changes in fetal development, and immune maturation.
“In recent years, the human microbiome has received increased attention as a potential contributor to disease development, especially the earliest microbial compositions,” the researchers say. To examine the effect of omega-3 and vitamin D supplements during pregnancy on the risk of asthma in newborns, Hans Bisgaard at the University of Copenhagen and his colleagues analyzed microbiota samples from 695 pregnant women and their children.
The participants were recruited from the Copenhagen Prospective Studies on Asthma in Childhood 2010, a large study of infants born to asthmatic mothers in Denmark. The researchers randomly administered some of the women a daily dose of two omega-3 fatty acids in the form of fish oil from week 24 of pregnancy to one week postpartum. The control group received a daily dose of olive oil. Similarly, the team randomly assigned some of the women to a group that received daily vitamin D3 tablets. In this case, the control group received a placebo tablet each day.
The team collected microbiota samples from the vagina of women at 24 and 36 weeks of pregnancy. The researchers also acquired infant microbiota samples at one week, one month, and three months of age, and infant fecal samples one week, one month, and one year after birth.
The average bacterial composition of maternal vaginal samples appeared similar and was dominated by Lactobacillus and Gardnerella bacteria. Fecal samples from one-week and one-month-old infants were instead dominated by Bifidobacterium, Enterobacteriaceae, and Bacteroides. One year later, the level of Enterobacteriaceae, Staphylococcus, Streptococcus and Bifidobacterium decreased in favor of Bacteroides and other microbes, including Faecalibacterium and Prevotella.
In airway samples from one-week-old infants, the three major genera were Staphylococcus, Streptococcus, and Moraxella. One month and three months after birth, the researchers observed an increase in the abundance of Streptococcus, Moraxella, and Haemophilus, and a decrease in Staphylococcus.
Supplements of vitamin D and omega-3 during pregnancy didn’t affect neither the infants’ gut microbiota nor their airway microbiota at one week and three months of age. But the dietary interventions did change the airway microbiota of one-month-old babies, leading to a substantial decrease in Firmicutes and a corresponding increase in Proteobacteria.
However, the team found that the changes in the one-month-old infants’ airway microbiota could account for only a small part of the total asthma prevention effect of omega-3 and vitamin D supplements. This suggest that the microbial changes observed as a result of dietary interventions had a minor effect on later risk of asthma, the researchers say. The clinical effects of omega-3 and vitamin D supplements, they add, “are probably working through many different mechanistic pathways.”