The primary objective of this pilot study is to determine if consumption of a probiotic yogurt causes reduced levels of environmental toxins in a group of school-aged Tanzanian children. The secondary objective is to determine the levels of environmental toxins in Tanzanian children and compare these to literature values of levels believed to negatively affect health and development. The third objective is to analyze the intestinal microbiota of the children and to determine if consumption of a probiotic yogurt has a significant affect on the microbiota composition.

A group of 60 first year students from the Lake Primary School will be recruited for inclusion into the study. After gaining consent from the child's caregiver, each child will be given a participant number and blood, urine and fecal samples will be collected from each child by qualified personnel from NIMR. Children will be randomized into two groups (n=30) to match age, sex and weight, one of which will receive a 100 g probiotic yogurt containing Lactobacillus rhamnosus GR-1 while the other group will receive an equivalent portion of milk. After 30 days of consuming the yogurt or milk, samples will again be collected.

Samples will be shipped back to London, Ontario Canada on dry ice for analysis. Blood and urine will be analyzed via high-resolution sector field inductively coupled plasma mass spectrometry (HR-SF-ICP-MS) to determine levels of toxic heavy metals (Mercury, Lead, Cadmium, Arsenic). This will be carried out by the London Health Sciences Trace Elements laboratory in Canada. Urine will also be analyzed via gas chromatography/ mass spectrometry (GC-MS) to determine levels of pesticides at the Biotron Facility (University of Western Ontario). We will also examine urine via NMR for potential host metabolic changes in response to probiotic instillation.

Bacterial community DNA samples will be extracted and analyzed to determine the gastrointestinal microbiota of the children both before and after administration of the probiotic yogurt to determine the effect of the yogurt on the gut microbiome. Briefly, DNA will be extracted with the Qiagen Stool DNA extraction kit and bacterial community 16S rRNA genes will amplified using barcoded primers specific for a variable region within the gene. The samples will be pooled and sequenced on the Ion Torrent platform (London Regional Genomics Center, Canada). Reads are then processed and analyzed using custom scripts as well as the Quantitative Insights Into Microbial Ecology (QIIME) tool, which is the leading package for microbiota analysis.

Inclusion Criteria:

• Aged 6-10
• Attends Lake Primary School (Mwanza, Tanzania)

Exclusion Criteria:

• Allergic to milk/ milk products
• Lactose intolerant