Heavy coffee drinking poses CVD mortality risk in presence of severe hypertension

Individuals with severe hypertension may do well to refrain from drinking too much coffee, as it contributes to an increased risk of cardiovascular disease (CVD) death, a study has found.

Compared with nonconsumption, coffee intake of ≥2 cups/day raised the risk of CVD death by twofold (hazard ratio [HR], 2.05, 95 percent confidence interval [CI], 1.17–3.59) among people with stage 2–3 hypertension. The corresponding risk estimates associated with intakes of <1 cup/day and 1 cup/day were 0.98 (95 percent CI, 0.67–1.43) and 0.74 (95 percent CI, 0.37–1.46), respectively (p=0.09 for trend). [J Am Heart Assoc 2022;doi:10.1161/JAHA.122.026477]

Meanwhile, heavy coffee drinking did not carry such a risk among those with optimal, normal, and high‐normal blood pressure (BP), as well as mild hypertension.

“Caffeinated coffee, which contains ingredients such as chlorogenic acid and other phenolic compounds, magnesium, and trigonelline, has been shown to lower serum cholesterol levels, improve endothelial function, and reduce inflammation in women with diabetes. Habitual coffee drinkers can also develop caffeine tolerance, which may reduce the adverse effects of caffeine on CVD outcomes,” the investigators explained. [Am J Clin Nutr 2006;84:888-893; Diabetes Care 2008;31:504-507; Vasc Health Risk Manag 2008;4:963-970]

“The harmful cardiovascular effects of caffeine (ie, transient blood pressure [BP] elevation) would be offset by the beneficial effects of these other components and tolerance to caffeine in the general population. However, because people with hypertension are more susceptible to the effects of caffeine, caffeine's harmful effects may outweigh its protective effects and increase the risk of mortality in people with severe hypertension,” they added. [Hypertension 2000;36:137-141]

The study used data from the JACC (Japan Collaborative Cohort Study for Evaluation of Cancer Risk) and included 18,609 participants (6,574 men and 12,035 women) aged 40–79 years at baseline. All of them completed a lifestyle, diet, and medical history questionnaire, underwent health examinations, and were followed for a median of 18.9 years. A total of 842 CVD deaths were recorded during the follow-up.

Across all BP categories, participants who drank more coffee tended to be younger, be current smokers, be current drinkers, eat fewer vegetables, and have higher total cholesterol levels and lower systolic BP.

Does green tea carry the same risk?

The investigators also examined the effect of caffeinated green tea consumption on the risk of CVD mortality across multiple BP categories. Generally, participants who drank higher amounts of green tea were more likely to be older and less likely to be unemployed, be smokers, or eat fruits. Among those with stage 2–3 hypertension, higher green tea consumption correlated with a lower total cholesterol level.

Green tea consumption was not associated with an excess risk of CVD mortality across all BP categories.

“[T]he mechanism underlying the beneficial effects of green tea may be explained by the effect of (−)‐epigallocatechin3‐gallate, the most abundant polyphenol in green tea,” according to the investigators.

In animal studies, (−)‐epigallocatechin3‐gallate has been show to significantly lower BP levels and enhance endothelial function in hypertensive rats. In addition, this green tea component can also reduce oxidative stress, attenuate inflammation, and improve the plasma lipid profile. [Med Sci Monit 2007;13:BR40-BR45; Am J Physiol Endocrinol Metab 2007;292:E1378-E1387; Naunyn Schmiedebergs Arch Pharmacol 2016;389:1225-1234; Front Immunol 2017;8:433; J Nutr Biochem 2007; 18:179-183]

“These beneficial effects of green tea catechins may partially explain why only coffee consumption was associated with an increased risk of mortality in people with severe hypertension despite both green tea and coffee containing caffeine,” the investigators said.

“To the best of our knowledge, this is the first study to find a positive association between heavy coffee consumption and CVD mortality among people with severe hypertension… More research is needed to confirm the effects of coffee and green tea consumption [in] hypertension,” they added.