Relationship between synbiotic components in the diet of atopic mothers and the synbiotic composition of breast milk. A hypothesis generating study.

Rationale
The gut microbiome plays a key role in a healthy immune development of infants, including the prevention of allergies. During the prenatal and postnatal period the intestinal microbial colonization of the infant is established. Diet strongly influences microbial colonization.
Naturally, breast milk is the first type of nutrition encountered by infants. However, there are conflicting results on the preventive effect of breast feeding on allergy development in the infant, although most studies found a protective effect.
The following components in breast milk are of specific interest for allergy prevention, based on their influence on the gut microbiome:
1. human milk oligosaccharides (HMOs), because HMOs serve as a prebiotic substrate for the infant’s gut bacteria, inducing a beneficial bifidogenic composition
2. butyrate, a short chain fatty acid and metabolite of microbial fermentation
3. the microbial content in breast milk, acting like natural probiotics and interacting with the microbiome of the infant’s gut.
Although it is known that diet influences the composition of breast milk, only few studies have focused on this topic. It is unknown if HMOs, butyrate or the microbial composition of breast milk, in other words the synbiotic components of breast milk, can be modified by the mother’s diet, e.g. by dietary fiber or the microbial content. Dietary fiber is crucial for a healthy gut microbiome and food-derived microbes are of interest because the consumption of food-derived microbes varies considerably, between 105 and 1011 microbes (or 10.7 -10.11 lactobacillae) per day in Dutch adults.

We hypothesize that the synbiotic composition of the diet of the mother is reflected in the synbiotic composition of breast milk and supports the prevention of allergic disease in the infant. In this process, the microbiome of the mother and the infant play a role.
It was shown that bacteria from probiotic supplements (lactobacillus and bifido bacteria) in breast feeding mothers could be found in breast milk and significantly increased the lactobacillus and bifido bacteria in breast milk. No differences were found between colostrum and mature milk with regard to the amount of lactobacillus and bifido bacteria. In our nutrition lactobacillae are the major source of microbial intake.
Therefore, the primary aim of the Synbio-breast study is to study the influence of the amount of lactobacillae in the diet of the mother on the amount of lactobacillae in mature breast milk (4 weeks post partum).
The primaire outcome measure is the amount of lactobacillae/ml in mature breast milk (logCFU), 4 weeks post partum.

The secondary aims are to study the influence of the diet of the mother , specifically dietary fiber and/or the total microbial composition, 3 days and 4 weeks post partum, on secondary outcome measures:
a. the amount and types of remaining microbes in breast milk
b. the amounts and types of HMOs in breast milk
c. the amount of butyrate in breast milk

The synbiotic composition of the diet of the mother is reflected in the synbiotic composition of breast milk and sustains the prevention or promotion of the development of allergic disease in the infant.

Primary outcome, 4 weeks post partum:
Amount of lactobacillae/ml in mature breast milk (logCFU), 4 weeks post partum, measured by IS-pro or 16S sequencing
Secondary outcomes, 3 days and 4 weeks post partum:
- amount of remaining microbes in breast milk, by IS-pro or 16S sequencing, as well as conventional plating
- the amounts and types of HMOs in breast milk by CGE-LIF.
- the amount of butyrate in breast milk.by gas chromatography.

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