Table 3.

Potential confounders on gut microbiome associations.

Potential confounder on alpha diversity	Statistical test	p-value
Time of day	ANOVA: grouped by AM and PM time of stool collection	p = 0.38
Seasonality	ANOVA: grouped by season (divided into spring, summer, autumn, winter)	p = 0.08
Coffee intake	ANOVA: Three groups based on mean daily coffee intake (last 7 day FFQ) 0–0.3 ml/d 0.3–45 ml/d >45 ml/d	p = 0.069
Sex	t.test: segregated by sex	p = 0.94
Medication	Not tested due to limits in sample size (esp. sample 2)	–
% body fat mass	Partial correlations for all correlations shown in Figs. 2–4 adjusted for % body fat mass	see SI Table 5

Most of these additional exploratory analyses could be performed in sample 1 only, due to limited information in sample 2.