Fig. 3. Associations between dietary habits and plasma metabolites.

a, Summary of the associations between diet and metabolites. The bars represent dietary habits, with the bar order sorted by the number of significant associations. Association directions are colored differently: orange indicates a positive association, whereas blue indicates a negative association. The length of each bar indicates the number of significant associations at FDR < 0.05 (Spearman; two sided). b, Association between plasma quinic acid levels and coffee intake. The x and y axes indicate residuals of coffee intake and the metabolic abundance after correcting for covariates, respectively (n = 1,054 biologically independent samples). c, Association between plasma 2,6-dimethoxy-4-propylphenol levels and fish intake frequency (n = 1,054 biologically independent samples). The x and y axes refer to residuals of fish intake and metabolic abundance after correcting for covariates, respectively. d, Differential plasma levels of 1-methylhistidine between vegetarians and non-vegetarians (n = 1,054 biologically independent samples). The y axis indicates normalized residuals of metabolic abundance. The P value from the Wilcoxon test (two sided) is shown. The box plots show the median and first and third quartiles (25th and 75th percentiles) of the metabolite levels. The upper and lower whiskers extend to the largest and smallest value no further than 1.5× the IQR, respectively. Outliers are plotted individually. e, Association between the diet quality score predicted by the plasma metabolome (y axis) and the diet quality score assessed by the FFQ (x axis) (n = 237 biologically independent samples). In b, c and e, each gray dot represents one sample, the dark gray dashed line shows the linear regression line and the gray shading represents the 95% CI. In b and c, the association strength was assessed using Spearman correlation (two sided; the correlation coefficient and P value are reported) and in e, the prediction performance was assessed with linear regression (F-test; two sided; the adjusted r² value and P value are reported).