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In Reply—Caffeine Effects on Arterial Stiffness: To Drink or Not to Drink
GUESSOUS, Idris, PONTE, Belen
GUESSOUS, Idris, PONTE, Belen. In Reply—Caffeine Effects on Arterial Stiffness: To Drink or Not to Drink. Mayo Clinic Proceedings , 2018, vol. 93, no. 8, p. 1150-1151
DOI : 10.1016/j.mayocp.2018.06.007 PMID : 30077208
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excreted in urine. However, the con- centration of these metabolites in urine is subjected to many confounding fac- tors. For example, it is reported that the rate of caffeine metabolism is vari- able, with caffeine consumers being slow, intermediate, or fast metaboliz- ers. This is highly attributable to ge- netic factors related to the CYP1A2 phenotype and liver function in gen- eral,4 and it is important to be taken into account when assessing caffeine health effects using urinary caffeine metabolites. Also, variability in excre- tion highly depends on the timing of the last intake of caffeine and previous habitual consumption.5 Ponte et al assessed the timing of the last intake of a caffeinated beverage, but it was not very clear whether this parameter was used as a confounding factor in the analysis. Also, habitual caffeine consumption should be taken into account. Previous studies have shown that people are more sensitive to the diuretic effect of caffeine after a short period of abstinence from caffeinated beverages compared with regular con- sumers; this results in an increased caffeine clearance.5,6Use of high regu- lar consumers in the same analysis with high nonregular consumers may have confounded the results. It is likely that stratification for habitual vs non- habitual caffeine consumers might pro- vide a clearer outcome. Finally, specific types of coffee, beyond caffeine per se (ie, Greek coffee), may exert more favorable effects on vascular properties (ie, endothelial function),7 which is another interesting field for further investigation.
In addition, data regarding caffeine consumption are lacking although the authors make conclusions regarding caffeine intake. The authors have previ- ously published in the same popula- tion study that caffeine consumption, assessed using food frequency ques- tionnaires, is associated with caffeine urinary metabolites. These question- naires offer valuable information in epidemiological studies, but are subject
to recall bias. Also, they give a sense of the frequency of consumption of spe- cific amounts of caffeinated beverages, in a short period of time rather than the specific amount consumed the day of the 24-hour urine collection.
Perhaps using 24-hour dietary recalls or even food diaries would offer better information regarding actual caffeine intake during the day of the urine collection and the previous day;
this is to match intake with caffeine urine metabolites and consequently to more accurately assess their association with PP and PWV. In our view and on the basis of available data, we have a lot more to learn concerning the effects of caffeine intake on arterial wall proper- ties and blood pressure.
Kalliopi Karatzi, PhD Department of Nutrition and Dietetics Harokopio University of Athens Athens, Greece
Theodore G. Papaioannou, PhD Biomedical Engineering Unit, First Department of Cardiology, Hippokration Hospital Medical School, National and Kapodistrian University of Athens Athens, Greece
Theodora Psaltopoulou, PhD Department of Hygiene, Epidemiology and Medical Statistics, School of Medicine National and Kapodistrian University of Athens, Athens, Greece
Dimitris Tousoulis, PhD Biomedical Engineering Unit, First Department of Cardiology, Hippokration Hospital Medical School, National and Kapodistrian University of Athens Athens, Greece
Potential Competing Interests: The authors report no competing interests.
1. Papaioannou TG, Karatzi K, Karatzis E, Papamichael C, Lekakis JP. Acute effects of caffeine on arterial stiff- ness, wave reflections, and central aortic pressures.
Am J Hypertens. 2005;18(1):129-136.
2. Ding M, Bhupathiraju SN, Satija A, van Dam RM, Hu FB. Long-term coffee consumption and risk of cardiovascular disease: a systematic review and a dose-response meta-analysis of prospective cohort studies.Circulation. 2014;129(6):643-659.
3. Ponte B, Pruijm M, Ackermann D, et al. Associa- tions of urinary caffeine and caffeine metabolites
with arterial stiffness in a large population-based study.Mayo Clin Proc. 2018;93(5):586-596.
4. Crews HM, Olivier L, Wilson LA. Urinary biomarkers for assessing dietary exposure to caffeine.Food Addit Contam. 2001;18(12):1075-1087.
5. Perera V, Gross AS, Forrest A, et al. A pharmacometric approach to investigate the impact of methylxanthine abstinence and caffeine consumption on CYP1A2 ac- tivity.Drug Metab Dispos. 2013;41(11):1957-1966.
6. Maughan RJ, Griffin J. Caffeine ingestion andfluid bal- ance: a review.J Hum Nutr Diet. 2003;16(6):411-420.
7. Siasos G, Oikonomou E, Chrysohoou C, et al. Con- sumption of a boiled Greek type of coffee is asso- ciated with improved endothelial function: the Ikaria study.Vasc Med. 2013;18(2):55-62.
https://doi.org/10.1016/j.mayocp.2018.06.008
In Reply d Caffeine Effects on Arterial Stiffness: To Drink or Not to Drink
To the Editor:We thank Karatzi et al for their letter and the issues they raised. The authors stressed the fact that the rate of caffeine metabolism is variable and that it is highly attributable to genetic factors related to the CYP1A2 phenotype and liver function in gen- eral. We cannot agree more and have actually acknowledged this in the Lim- itation section of our article as follows:
“although we considered major factors, the biological half-life of caffeine is highly variable among individuals (2- 10 hours) and is influenced by several genetic and nongenetic determinants (eg, liver function) that we could not account for.”1It is true that information on habitual caffeine consumption, period of abstinence, and types of cof- fee could have been useful to further control for potential confounding.
We fully agree with Karatzi et al who underscore that questionnaires on caffeine intake are subject to recall bias. This is the reason why we have collected in our study objective infor- mation using caffeine urinary excretion instead of self-reported intake.
Although Karatzi et al suggested that 24-hour dietary recall or even food di- aries would offer better information regarding caffeine intake, we believe that these questionnaires are not MAYO CLINIC PROCEEDINGS
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much more immune to bias as compared with other questionnaires.
In addition, the use of these question- naires would not help us in decipher- ing the role of caffeine metabolites, namely, paraxanthine, theobromine, and theophylline, in cardiovascular health. Using data from urinary excre- tion instead of questionnaires, we found strong positive associations of paraxanthine and theophylline with arterial stiffness. Thisfinding is in line with the fact that paraxanthine is a very potent methylxanthine, and even slightly more potent than caffeine.
Regarding the timing of the last caffeinated beverage, it was stan-
dardized, but indeed we have not adjusted the analyses for that param- eter. We also have not systematically collected information on the different types of coffee.
Finally, we fully agree with the au- thors that we all have a lot more to learn concerning the effects of caffeine intake on arterial wall properties and blood pressure. We hope that our study will encourage further research to increase knowledge in thisfield.
Idris Guessous, MD, PhD Lausanne University Hospital Division of Chronic Diseases Institute of Social and Preventive Medicine Lausanne, VD, Switzerland
Geneva University Hospitals Unit of Population Epidemiology Department of Community Medicine Primary Care and Emergency Medicine Geneva, GE, Switzerland
Belen Ponte, MD Geneva University Hospitals Nephrology Division Department of Medicine Specialties Geneva, GE, Switzerland
Potential Competing Interests: The authors report no competing interests.
1. Ponte B, Pruijm M, Ackermann D, et al. Associations of urinary caffeine and caffeine metabolites with arterial stiffness in a large population-based study.Mayo Clin Proc. 2018;93(5):586-596.
https://doi.org/10.1016/j.mayocp.2018.06.007
LETTERS TO THE EDITOR
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