The habit of consuming more than three cups of coffee a day increases in up to four times the chance of genetically predisposed individuals to present high levels of blood pressure. The conclusion is from a study carried out at the University of São Paulo (USP) and published in the Clinical Nutrition magazine.
The study, supported by FAPESP, was based on data from 533 people interviewed in the Health Survey of the Municipality of São Paulo (ISA-Capital 2008), a population-based study that covers the urban area of the capital and assesses the health conditions of its residents. No significant association was observed between drinking and blood pressure levels in the case of people who consumed up to three cups aday.
"These findings highlight the importance of moderating coffee consumption for the prevention of high blood pressure, particularly in individuals genetically predisposed to this cardiovascular risk factor," Andreia Machado Miranda, a postdoctoral fellow in the Department of Nutrition at the USP School of Public Health (FSP-USP) and first author of the article, told Agência FAPESP.
Values above 140 by 90 millimeters of mercury (mmHg) were considered as high blood pressure. In a previous study, also based on data from the ISA-Capital 2008, Miranda had observed that moderate coffee consumption (one to three cups daily) has a beneficial effect on some cardiovascular risk factors - particularly blood pressure and blood levels ofhomocysteine, an amino acid related to the appearance of alterations in blood vessels, heart attack and stroke. In this first analysis, genetic data were not included.
"We decided in the most recent study to investigate whether in individuals who have genetic factors that predispose to hypertension coffee consumption would have an influence on blood pressure levels," Miranda said.
Through a questionnaire applied to more than 3,000 participants, the ISA-Capital 2008 obtained sociodemographic and lifestyle data, such as age, gender, race, per capita family income, physical activity and smoking. Two recordings were also made to evaluate food consumption and blood was collected for biochemical analysis and DNA extraction for genotyping,during a home visit made by a nursing technician, the weight, height and blood pressure of the volunteers.
A representative sample of 533 adults and elderly was selected for the analyses conducted at FSP-USP. Inclusion criteria included the presence of information on daily coffee consumption and on the presence or absence of the genetic risk variants for high blood pressure.
Based on information described in the scientific literature, the researchers identified in the data available in ISA-Capital 2008 four polymorphisms (variants of the genes studied) capable of indicating predisposition to hypertension: CYP1A1 / CYP1A2 (rs2470893, rs2472297); CPLX3/ULK3 (rs6495122); and MTHFR (rs17367504).
A genetic risk score ranging from zero to eight was then created. If the individual was homozygous dominant (no variant allele) he/she would score zero, if he/she was heterozygous (one variant allele) he/she would score one, and if he/she was homozygous recessive (two variant alleles), two. The final score is obtained by summing the number of risk alleles of the four polymorphismsanalyzed.
Coffee consumption was divided into three categories: less than one cup a day; one to three; and more than three cups daily.
"We did an association analysis of these three factors: genetic risk score, coffee consumption, and blood pressure value. Using a statistical method known as multiple logistic regression, we included other adjustment variables that could influence the outcome, such as age, gender, race, smoking, alcohol consumption, body mass index, physical activity, and use ofantihypertensive medication", explained Miranda.
The statistical analyses showed that as the risk score and the amount of coffee consumed increased, so did the chance of the individual presenting high blood pressure. In the volunteers with the highest score and daily consumption of more than three cups, the chance of high blood pressure was four times higher than in people without genetic predisposition.
"Since most of the population has no idea whether or not they are predisposed to develop hypertension - to do so would require sequencing and genome analysis - the ideal is for everyone to make a moderate consumption of coffee which, it seems, is beneficial to heart health," Miranda said.
According to the researcher, recent studies have shown that moderate consumption of the beverage can help prevent calcification of the coronary artery. The beneficial effect is attributed to polyphenols, bioactive compounds found in abundance in coffee. The action on blood pressure, according to Miranda, is related to caffeine.
According to the most recent guidelines of the American Heart Association, in healthy individuals, moderate coffee consumption does not increase the risk of heart disease and is not associated with long-term damage to health.
Miranda's doctorate research was supervised by FSP-USP professor Dirce Marchioni. Now, in the post-doctorate, also with the support of FAPESP, the objective is to evaluate the effect of coffee consumption in patients with cardiovascular disease - particularly the acute coronary syndrome, caused by obstruction in the coronary artery, which irrigates the heart.
The group intends to analyze, for four years, the follow-up data of 1,085 patients who suffered acute myocardial infarction or unstable angina, were treated at the University Hospital of USP and are part of the cohort of the longitudinal study Strategy of Coronary Insufficiency Registry (Erico).
"The idea is to evaluate, over the years, the influence of coffee consumption on the survival of these patients," Miranda said.
In Marchioni's evaluation, the research started during Miranda's doctorate brought relevant results. "Coffee proved to be an important contributor to the intake of polyphenols in the population studied and this bioactive compound has been associated with several health benefits. When investigating coffee consumption and its association with some health conditions, we identified that the consumptionmoderate can be beneficial and, therefore, can compose the usual diet, always avoiding exaggeration", said.
The scientific article was published in Clinical Nutrition and can be read by clicking here .