Pilot studies, such as this one, play an important role in health research to develop, assess, and adapt the methods employed, generate hypotheses and provide information for a sample size calculation for a larger trial , . Using the results generated in this study, a power analysis was undertaken using the MultiPower method in R , to calculate the optimal sample size for each group comparison integrating both metabolomics/exposomics (1,003 chemicals, Table ), and metagenomics (163 mOTUs, Table ) datasets to help scope future studies. For an average statistical power of 0.8, the estimated minimum sample size for each group in metabolomics/exposomics ranges between 40 and 89, while for metagenomics it is 36-79. The overall optimal sample size would thus be 273 (Table for details), and the minimum sample size required per group comparison and omic dataset (metabolomics and metagenomics) is shown in Figure , which is a challenge for specialized cohorts such as this one.