Relationship of Coffee Consumption and its Urinary Biomarker to Blood Pressure: The Intermap Study

Background: Coffee, one of the most commonly consumed beverages, is complex, with substantial differences in chemical composition among cups, depending on the origin of the product, how it is processed and prepared. Studies suggest that coffee consumption may help prevent several chronic diseases, e.g., Alzheimer’s disease, type 2 diabetes, and breast cancer. After caffeine, the second most abundant compound in coffee is trigonelline, also known as N -Methylnicotinic acid (NMNA), a niacin-related compound. Coffee contains about 10-40 mg of niacin per 100 g (the daily recommended dose of niacin is 14 mg for women and 16 mg for men). The influence of coffee on blood pressure (BP) is not clear; only the effect of caffeine has been studied extensively. Objective: To investigate associations of coffee consumption with the level of its urinary biomarker NMNA, and their relationships with BP among 2,157 US men and women ages 40-59 from the International Collaborative Study on Macro-/Micronutrients and Blood Pressure (INTERMAP). Methods: The INTERMAP Study is a cross-sectional epidemiologic investigation with standardized quality-controlled methods; four 24-hour dietary recalls; 2 timed 24-hour urine collections, 8 BP measurements, and questionnaire data were accrued. Proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy was performed to obtain urinary metabolite profiles for all participants. Urinary NMNA was calculated from area under the curve of a triplet at δ 8.84 in each spectrum, and was expressed as a relative integral. Associations of BP with consumption of coffee and urinary NMNA, were assessed by multiple linear regression; possible confounders included age, gender, population sample, 24-hr urinary sodium and potassium excretions, and dietary variables. Results: Mean coffee consumption was 400 mg/day; relative urinary NMNA integral was 0.001. Sex-age-sample adjusted correlation (r) between urinary NMNA level and coffee consumption was 0.76 for mg/day; r between NMNA and niacin intake was 0.08; r between coffee and niacin, 0.16. There was a non-significant positive association between coffee intake and BP in all regression models adjusted for confounders including height and weight; data for relation of NMNA with BP were qualitatively similar to the foregoing. With adjustment for possible confounders, differences in systolic blood pressure (SBP) were 0.5 mm Hg (95% CI, -0.7 to 1.6) for coffee intake higher by 2 SD, 900 mg/day. Differences in SBP for 2 SD urinary NMNA integral were similar, 0.5 mm Hg (-0.6 to 1.7). For hypertensive participants, difference in SBP was 2.3 mm Hg (-0.7 to 5.4) for coffee intake 2 SD higher, and 2.7 mm Hg (-0.4 to 5.7) for urinary NMNA integral 2 SD higher. Conclusion: Higher coffee intake may raise BP, especially among hypertensive persons. Urinary NMNA apparently is a good biomarker for validation of coffee consumption among free-living people.