AHA study: Heavy coffee drinking may pose CVD risk in patients with hypertension

By Carol Nathan | Medically reviewed by James Beckerman, MD, FACC
Published April 25, 2023

Key Takeaways

  • Several new studies report conflicting results regarding how coffee consumption affects health.

  • Heavy coffee drinking increases the risk of cardiovascular disease (CVD) mortality in some patients but moderate consumption can be beneficial for others.

  • HCPs may want to advise patients with severe hypertension to reduce heavy coffee drinking.

The debate as to whether coffee is a benefit or risk for some patients just got clarified further with an American Heart Association (AHA) study showing that heavy coffee consumption increases the risk of mortality from cardiovascular disease (CVD) in people with severe hypertension, whereas green tea does not.

It is worth looking at the details of this study, and to review the results from other new coffee studies. Information on how coffee affects people with diabetes and rheumatoid arthritis (RA) will be helpful to HCPs as they advise their patients. 

Coffee vs tea effect on CVD mortality

A new study published in the Journal of the American Heart Association has provided some concerning results on coffee drinking. 

This large prospective, observational Japanese study of more than 18,000 participants looked at the impact of coffee vs green tea consumption on CVD mortality among people with various levels of hypertension.[]

The main finding was that heavy coffee drinking of more than 2 cups a day was associated with twice the CVD mortality in people with severe hypertension, compared with no coffee consumption. Heavy coffee consumption was not associated with an increased risk of CVD mortality in people without hypertension or with grade-1 hypertension. 

In contrast, green tea consumption was not associated with an increased risk of CVD mortality across any hypertension category. 

"This is the first study to find a positive association between heavy coffee consumption and CVD mortality among people with severe hypertension."

Authors, Journal of the American Heart Association

The authors also state that heavy coffee consumption should therefore be avoided by people with severe hypertension.

Metabolic syndrome and rheumatoid arthritis 

A study from China looked at the association between coffee consumption and metabolic syndrome severity among 1,094 participants with self-reported RA in the NHANES database.[]

Drinking more than 2 cups of coffee daily was associated with a decrease in the severity of metabolic syndrome, according to their metabolic syndrome (MetS) z-score (a widely used tool to evaluate MetS). 

The authors note that RA has historically been associated with a higher incidence of metabolic syndrome and insulin resistance due to the associated hyper-inflammatory state involved. Metabolic syndrome refers to a constellation of factors that include central obesity, hypertension, high triglycerides, and low levels of high-density lipoprotein cholesterol (HDL-C).

The authors of the study theorized about the mechanisms for the positive effects of daily coffee intake on metabolic syndrome in the patients with RA. The beneficial effects, they wrote, might be due to effects of coffee on BMI, blood pressure, and insulin resistance. In the study, the investigators did not find any significant differences between caffeinated and decaffeinated coffee. 

Effect on development of diabetes 

News about how coffee drinking may affect the development of diabetes comes from a study conducted by an international team of investigators.[] 

The study focused on women with a history of gestational diabetes, who are known to be at higher risk for type-2 diabetes later in life. The study was designed to determine whether greater habitual coffee drinking would be associated with a lower risk of type-2 diabetes among these women.

This was a prospective study in which 4,522 participants were followed for 26 years. Overall, type-2 diabetes developed in 979 participants. Consumption of caffeinated coffee was found to be inversely related to the risk of type-2 diabetes. In addition, greater caffeinated coffee consumption was associated with lower fasting insulin and C-peptide concentrations. 

Investigations into the health effects of coffee could be aided by analyzing urine samples for specific metabolites as biomarkers for coffee consumption. Although incorporating routine urine samples into multiyear studies could be a logistical challenge, the approach has merit. This is because a urine biomarker for coffee consumption has been found, according to a study published in Food Chemistry.[]

The urine for the investigation was obtained from individuals who self-reported their coffee consumption (which can be unreliable).

The researchers identified three metabolites that are products of substances formed in large quantities during coffee roasting, but are rarely found in any other foods. In addition, the biomarkers can be detected in very small amounts of urine, making them appealing for use in future clinical research. 

What this means for you 

It can be difficult to advise patients about the health benefits or detriments of drinking coffee, because the research seems to generate conflicting results. Based on the studies reviewed here, it makes sense to advise patients with severe hypertension to reduce heavy drinking of coffee, and to switch to drinking green tea. In patients with rheumatoid arthritis or gestational diabetes, it is reasonable to tell patients to continue with their coffee consumption. 

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