TABLE 3.

Serum metabolites associated with self-reported total coffee intake by type of coffee consumption compared with nonconsumers in a nested case-control study within the PLCO Cancer Screening Trial (n = 478)¹

	Coffee-metabolite associations by type of coffee consumption
	Caffeinated only compared with none (n = 257)		Decaffeinated only compared with none (n = 182)		Mixed compared with none (n = 183)
Serum metabolite	Partial Pearson correlation	P	Partial Pearson correlation	P	Partial Pearson correlation	P
Trigonelline (N′-methylnicotinate)	0.593	5.54 × 10−46*	0.426	3.76 × 10−22*	0.523	1.81 × 10−34*
Quinate	0.569	1.01 × 10−41*	0.471	1.96 × 10−27*	0.510	1.75 × 10−32*
X_12039	0.493	3.16 × 10−30*	0.357	1.23 × 10−15*	0.415	4.78 × 10−21*
X_13741	0.479	1.90 × 10−28*	0.338	5.05 × 10−14*	0.371	7.46 × 10−17*
X_12816	0.456	1.56 × 10−25*	0.289	1.70 × 10−10*	0.422	8.28 × 10−22*
X_14465	0.434	4.33 × 10−23*	0.262	7.36 × 10−9*	0.381	1.11 × 10−17*
X_14473	0.434	4.33 × 10−23*	0.262	7.36 × 10−9*	0.381	1.11 × 10−17*
X_17185	0.459	6.06 × 10−26*	0.278	8.19 × 10−10*	0.340	3.32 × 10−14*
X_12230	0.448	1.35 × 10−24*	0.298	4.26 × 10−11*	0.363	3.74 × 10−16*
Paraxanthine2	0.467	7.68 × 10−27*	0.109	1.81 × 10−2	0.354	2.59 × 10−15*
N-(2-furoyl)glycine	0.338	4.95 × 10−14*	0.236	2.26 × 10−7*	0.271	2.35 × 10−9*
Catechol sulfate	0.325	4.74 × 10−13*	0.253	2.45 × 10−8*	0.282	4.50 × 10−10*
Caffeine2	0.401	1.38 × 10−19*	0.057	2.16 × 10−1	0.297	5.03 × 10−11*
X_05426	0.343	2.01 × 10−14*	0.213	3.08 × 10−6*	0.272	2.10 × 10−9*
1-Methylxanthine2	0.417	3.38 × 10−21*	0.040	3.84 × 10−1	0.308	7.71 × 10−12*
Theophylline2	0.370	1.01 × 10−16*	0.029	5.32 × 10−1	0.303	1.81 × 10−11*
X_12329	0.306	1.12 × 10−11*	0.180	8.75 × 10−5	0.235	2.37 × 10−7*
1,3,7-Trimethylurate2	0.362	4.88 × 10−16*	0.010	8.32 × 10−1	0.225	8.23 × 10−7*
3-Hydroxyhippurate	0.212	3.43 × 10−6*	0.156	6.75 × 10−4	0.198	1.52 × 10−5*
1,7-Dimethylurate2	0.323	6.23 × 10−13*	0.052	2.62 × 10−1	0.196	1.80 × 10−5*
1-Methylurate2	0.271	2.29 × 10−9*	0.014	7.65 × 10−1	0.181	7.80 × 10−5
X_14291	0.183	6.53 × 10−5*	0.122	8.15 × 10−3	0.191	3.15 × 10−5*
X_14374	0.211	3.70 × 10−6*	0.132	4.04 × 10−3	0.148	1.29 × 10−3
Cyclo(leu-pro)	0.193	2.41 × 10−5*	0.130	4.62 × 10−3	0.139	2.47 × 10−3
4-Vinylphenol sulfate	0.191	2.88 × 10−5*	0.162	4.16 × 10−4	0.139	2.54 × 10−3
3-(3-Hydroxyphenyl) propionate	0.202	1.00 × 10−5*	0.125	6.76 × 10−3	0.150	1.13 × 10−3
Theobromine2	0.179	9.13 × 10−5*	0.059	2.01 × 10−1	0.133	3.70 × 10−3
X_12734	0.227	6.40 × 10−7*	0.145	1.64 × 10−3	0.175	1.36 × 10−4
Cinnamoylglycine	0.184	6.00 × 10−5*	0.095	3.98 × 10−2	0.202	1.02 × 10−5*

¹Only significant metabolites from the main analysis are shown; the type of coffee intake was self-reported during follow-up on the Dietary Health Questionnaire; individuals with missing types of coffee intake (n = 20) were excluded. Each group of comparisons included n = 47 nondrinkers. Metabolites with the prefix X_ are of unknown identity. Partial correlations were determined between ln(metabolite) and relevant ln(coffee) (grams per day of caffeinated, decaffeinated, or mixed) adjusted for sex, tobacco smoking status (current, former, never), age (continuous), and BMI (continuous). P values are from the linear regression of relevant ln(coffee) (grams per of caffeinated, decaffeinated, or mixed) on ln(metabolite) adjusted for sex, tobacco smoking status (current, former, and never), age (continuous), and BMI (continuous). *Significant associations from the linear regression of ln(metabolite) on ln(coffee). Bonferroni-corrected level of significance, P < 7.61 × 10⁻⁵. PLCO, Prostate, Lung, Colorectal, and Ovarian.

²Caffeine and known caffeine metabolites.