A study published in the Journal of the American Heart Association describes that excessive consumption of coffee can increase the risk of cardiovascular disease-related mortality in individuals with severe hypertension.
Study: Coffee and Green Tea Consumption and Cardiovascular Disease Mortality Among People With and Without Hypertension. Image Credit: Bohdan Malitskiy / Shutterstock
Background
Consumption of coffee is known to reduce the risk of hypertension and related mortality in the general population. However, it can cause a transient increase in blood pressure among individuals with hypertension.
Evidence shows that the beneficial effect of coffee consumption depends on the blood pressure levels of individuals. In severe hypertension patients, coffee can cause an acute increase in blood pressure, increasing the risk of cardiovascular disease.
On the other hand, the consumption of green tea is known to reduce blood pressure in patients with hypertension. Moreover, green tea reduces the risk of all-cause mortality and cardiovascular disease-related mortality in the general population.
In the current study, scientists have investigated the association between coffee or green tea consumption and the risk of cardiovascular disease-related mortality in Japanese men and women with varying degrees of hypertension.
Study design
A total of 18,609 individuals, including 6,574 men and 12,035 women, from 24 communities across Japan were enrolled in the study. The participants were asked to complete questionnaires to collect demographic characteristics, medical history, lifestyle, and diet information.
The baseline blood pressure of participants was measured by trained personnel. Based on the blood pressure levels, the participants were categorized into five groups, including optimal and normal blood pressure, high‐normal blood pressure, grade 1 hypertension, grade 2 hypertension, and grade 3 hypertension.
Important observations
The study explored the relationship between coffee consumption rate and baseline characteristics of the participants belonging to each blood pressure category. A higher rate of coffee consumption was observed among younger participants, current smokers, current drinkers, and fewer vegetable eaters. In addition, the participants with higher total cholesterol levels and lower systolic blood pressure were also likely to be more frequent coffee drinkers.
The study also explored the relationship between green tea consumption rate and baseline characteristics of the participants in each blood pressure category. A higher rate of green tea consumption was observed among older participants, frequent fruit eaters, and employed participants.
An association between higher green tea consumption rate and lower total cholesterol level was observed among participants with grade 2-3 hypertension.
Coffee consumption and risk of cardiovascular disease mortality
A total of 842 cardiovascular disease-related deaths occurred during the 18.9 years of the follow-up period.
The consumption of two or more cups of coffee a day was found to increase the risk of cardiovascular disease-related mortality among participants with grade 2-3 hypertension. In contrast, no such association was observed among participants with optimal and normal blood pressure, high-normal blood pressure, or grade 1 hypertension.
Green tea consumption and risk of cardiovascular disease mortality
The consumption of green tea was not found to increase the risk of cardiovascular disease-related mortality among participants with grade 1 to 3 hypertension.
Among participants with high-normal blood pressure or optimal/normal blood pressure, consuming 5-6 cups or 1-2 cups of green tea a day, respectively, slightly reduced the risk of cardiovascular disease-related mortality.
Green tea. Image Credit: Den Edryshov / Shuuterstock
Study significance
The study reveals that a high level of coffee consumption can cause 2-fold induction in the risk of cardiovascular disease-related mortality among individuals with severe hypertension but not among individuals without hypertension or grade 1 hypertension.
The study could not find any negative impact of green tea consumption on the risk of cardiovascular disease-related mortality among individuals with mild or severe hypertension.
Some components of caffeinated coffee, including chlorogenic acid, magnesium, and trigonelline, are known to have health benefits, including reduced blood cholesterol levels, inflammation, and improvement of endothelial functions. These positive effects nullify the negative cardiovascular effects of caffeine in the general population.
Considering current study findings, the scientists suggest that the higher susceptibility of individuals with severe hypertension to adverse effects of caffeine might actually offset its health benefits and increase the risk of fatality.
Caffeinated green tea, on the other hand, contains a high level of polyphenols, including epigallocatechin-gallate. Polyphenols have several health benefits, including anti-inflammatory, antioxidant, lipid-lowering, and blood pressure-lowering properties. The positive health effects of green tea catechins are sufficient to nullify the negative cardiovascular effects of caffeine.