Written by: Lauren Milligan Newmark, Ph.D. | Issue # 114 | 2023
- A prospective study of over 2,000 mothers and their infants found that yogurt-eating during the last trimester of pregnancy was associated with a lower risk of infantile eczema.
- As a fermented food, yogurt increases the number of beneficial bacteria in the pregnant mother’s gut microbiome.
- Researchers hypothesize that the pregnant mother’s gut microbes communicate with the fetal immune system and play a role in the development of allergies. Beneficial bacteria could help prevent allergy-prone phenotypes.
Pregnant mothers are often told they are eating for two. Although a myth from a caloric perspective (the energetic cost of pregnancy is only 300–400 extra calories per day , not double the mom’s caloric needs), there is truth to this old saying. The fetus eats what the mother eats: glucose, amino acids, and fatty acids from the mother’s breakfasts, lunches, and dinners travel from the maternal bloodstream across the placenta and fuel fetal growth and development.
But the mom’s food choices may do more than just help grow bones, skin, muscles, and organs. Mounting evidence [2-7] suggests the maternal gut microbiome—the composition of which is strongly influenced by the mother’s dietary choices—helps shape the development of the fetal immune system. Foods that improve the health of the mom’s gut microbiome, like probiotic-rich yogurt, are predicted to direct the immune system of the developing fetus away from inflammatory-prone responses, like allergies [5-7]. It sounds too good to be true, but adding foods like yogurt to the pregnant mother’s diet may be an important tool in allergy prevention.
A new study  tested this intriguing hypothesis in a population of Chinese mothers who were a part of the Tongji Maternal and Child Health Cohort (TMCHC) in Wuhan, China. Just over 2,300 mother-infant dyads were followed from 16 weeks of gestation through three months postnatally, and 2,114 of these dyads were followed for an additional three months. The researchers were specifically interested in the relationship between the mothers’ yogurt consumption during the last trimester of pregnancy and the incidence of eczema, an inflammatory skin condition, in the offspring at 3 months and 6 months of age. Eczema is typically the first sign of allergies in infants who will be prone to allergic reactions and was used by the research team as a proxy for an infant with an allergy-prone phenotype .
As predicted, yogurt consumption in pregnancy demonstrated a protective effect. Infants born to mothers who consumed any yogurt during their last three months of pregnancy had a lower risk of having an infant with eczema between three and six months of age compared with mothers who did not consume yogurt . The investigators also identified a dose-dependent effect of yogurt consumption. Every one time per week increase in yogurt consumption was associated with a 2% lower risk of infant eczema and every 10 grams per day increase was associated with a 3% lower risk of eczema in infants three to six months of age, and the lowest relative risk for eczema was associated with infants whose mothers had frequent yogurt consumption (defined in this study as at least three times per week or >50 grams of yogurt per day) . These findings were statistically significant even after controlling for potential cofounders including mother’s age, breastfeeding duration, maternal history of allergies, and probiotic supplementation, and established risk factors for infantile eczema like infant sex, birth season, or mode of delivery .
The results of the TMCHC study are in line with previous research on mother-infant dyads from Turkey  and Japan , both of which identified a protective effect of yogurt consumption during pregnancy on the development of infantile eczema. However, all three of these were prospective studies and did not investigate the mechanisms that linked the maternal gut microbiome with the fetal immune system. As a fermented food, yogurt consumption is understood to improve the composition of the mom’s gut microbiome by increasing the number of healthy gut microbes. Yogurt-eating has been associated with numerous physiological, metabolic, and immunological benefits to the consumer, including a lower risk for type 2 diabetes, cardiovascular disease, chronic inflammation, and dementia. But how do the microbes in the mother’s gut communicate with the developing fetus?
During pregnancy, the mother’s gut epithelium (the layer that separates her gut from her bloodstream) becomes more permeable. This physiological change is believed to facilitate greater interactions between the mom’s gut microbiome and her immune system . It is well known that mothers transfer their own immunoglobulin G (IgG) across the maternal-fetal barrier starting as early as 13 weeks of gestation. Researchers hypothesize that these placentally-transferred IgG are microbe-specific. Depending on the type of microbe, the IgG can educate the fetal immune system to have an inflammatory or anti-inflammatory response [5, 7]. Because eating yogurt increases the population of friendly microbes in the mother’s gut, the fetal immune system is predicted to be directed away from an allergy-prone phenotype [5-7].
Another potential mechanism for crosstalk between mother’s gut and fetus is gut-derived short-chain fatty acids (SCFA). SCFA are produced when gut bacteria in the large intestine break down indigestible dietary carbohydrates. SCFA from human milk are already implicated in allergy prevention in nursing infants. Researchers believe that during pregnancy, SCFA travel from the maternal gut to the fetal thymus (a gland that produces lymphocytes called T cells). There, they push those T cells in a non-inflammatory direction by interacting directly with the proteins that surround DNA [5-7]. By keeping certain sections of DNA turned on (or by turning certain sections of DNA off), SCFA can direct the T cells to develop into regulatory cells (aka Treg) or inflammatory cells. The current hypothesis from researchers working in this field suggests the transfer of SCFA from the maternal gut increases the concentration of fetal Treg cells, a process that is supported by animal models [5, 7].
Whether the links between the maternal gut microbiome and the fetal immune system are microbe-specific IgG, SCFA, or both is still being elucidated. But the potential for the maternal diet to influence fetal immunity is an exciting possibility. Dietary interventions during pregnancy often require mothers to give up certain foods. Adding yogurt seems infinitely easier than avoiding raw fish, deli meat, or soft cheeses and would also help pregnant mothers meet their calcium requirements, provide a source of protein, and improve the composition of her own gut microbiome—the potential for allergy prevention in the offspring seems to be an amazing bonus of “eating for two.”
- Dufour DL, Sauther ML. Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation. American Journal of Human Biology. 2002 Sep; 14(5): 584-602.
- Tan T, Xiao D, Li Q, Zhong C, Hu W, Guo J, Chen X, Zhang H, Lin L, Yang S, Xiong G. Maternal yogurt consumption during pregnancy and infantile eczema: a prospective cohort study. Food & Function. 2023; 14(4): 1929-36.
- Vuillermin PJ, Macia L, Nanan R, Tang ML, Collier F, Brix S. The maternal microbiome during pregnancy and allergic disease in the offspring. In: Seminars in Immunopathology 2017 Nov (Vol. 39, pp. 669-75). Springer Berlin Heidelberg.
- Macpherson AJ, de Agüero MG, Ganal-Vonarburg SC. How nutrition and the maternal microbiota shape the neonatal immune system. Nature Reviews Immunology. 2017 Aug; 17(8): 508-17.
- Kalbermatter C, Fernandez Trigo N, Christensen S, Ganal-Vonarburg SC. Maternal microbiota, early life colonization and breast milk drive immune development in the newborn. Frontiers in Immunology. 2021 May; 12: 683022.
- Nyangahu DD, Jaspan HB. Influence of maternal microbiota during pregnancy on infant immunity. Clinical & Experimental Immunology. 2019 Oct; 198(1): 47-56.
- Thomson CA, Mccoy KD. The maternal microbiome. The Scientist. 2021 Aug 1;35(4): 32-8.
- Celik V, Beken B, Yazicioglu M, Ozdemir PG, Sut N. Do traditional fermented foods protect against infantile atopic dermatitis. Pediatric Allergy and Immunology. 2019 Aug; 30(5): 540-6.
- Miyake Y, Tanaka K, Okubo H, Sasaki S, Arakawa M. Maternal consumption of dairy products, calcium, and vitamin D during pregnancy and infantile allergic disorders. Annals of Allergy, Asthma & Immunology. 2014 Jul 1; 113(1): 82-7.
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