All you need to know

Coffee vs. green tea:
impact of consumption on the risk of death from cardiovascular disease

Drinking two or more cups of coffee a day can increase the risk of cardiac death in people with severe hypertension. Conversely, green tea – such as matcha – would not increase the risk of mortality regardless of a person’s blood pressure level.

According to a Japanese study published in December 2022 in the Journal of the American Heart Association (JAHA) [1], drinking two or more cups of coffee a day was associated with twice the risk of death from cardiovascular disease in people with severe hypertension compared with non-coffee drinkers.

Coffee and green tea

Green tea and coffee are two very popular beverages that have been associated with numerous health benefits.

Green tea is rich in antioxidants, particularly catechins [2], which can help protect the body’s cells from free radical damage. Green tea has also been shown to help reduce the risk of heart disease, type 2 diabetes and certain types of cancer. Green tea can also help improve mental health by reducing stress and enhancing cognition.

Coffee, meanwhile, is an important source of caffeine, a substance that can stimulate the brain and improve alertness and concentration. Coffee can also help reduce the risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s. What’s more, coffee may help protect against certain metabolic diseases such as type 2 diabetes and obesity.

Finally, it’s important to note that these beverages should be consumed in moderation, and limited or avoided by frail or young people. Caffeine can cause nervousness, insomnia and other side effects in some people. It is therefore advisable to avoid excessive consumption. Likewise, it’s important to remember that green tea and coffee are no substitute for hydration, a balanced diet and regular physical activity as part of a healthy lifestyle.

A reminder of the benefits of coffee

Coffee can have a number of health benefits when consumed in moderation, i.e. around three cups a day for a healthy adult.

Here are just a few examples of the likely benefits identified in the various scientific studies on coffee:

  • Stimulation of alertness and attention: caffeine, the active ingredient in coffee, is a stimulant that can help maintain alertness and attention.
  • Improved memory and cognition: some studies have shown that caffeine consumption can improve short-term working memory and cognition in general.
  • Reduced risk of certain diseases: coffee consumption may be linked to a reduced risk of developing certain diseases, including Alzheimer’s disease, dementia, type 2 diabetes and certain types of cancer.
  • Improved mood and motivation: caffeine can help improve mood and motivation by acting on neurotransmitters in the brain.

It’s important to stress that these benefits are generally observed when coffee is consumed in moderation. Excessive coffee consumption can have undesirable effects, such as insomnia, irritability and headaches.

Coffee can also interfere with the absorption of certain nutrients and medications. It is therefore advisable to consume coffee and caffeine-based drinks in moderation.

Memento on the benefits of green tea

Green tea is a source of many health benefits. It contains antioxidants, notably catechin, which can help protect cells against damage caused by free radicals. Green tea can also help reduce the risk of heart disease by lowering blood pressure and lowering blood cholesterol levels.

In addition, green tea can aid weight loss by increasing metabolism and promoting the use of fat as an energy source. It can also slow skin ageing, or improve mental health by reducing stress and improving alertness and cognitive function.

Finally, green tea may have anti-inflammatory properties and may be beneficial in preventing certain forms of cancer, such as colon, prostate and breast cancer. However, all these effects have yet to be conclusively proven in clinical studies.

What is hypertension?

Hypertension [3] is a medical condition in which the blood pressure in the blood vessels is high. Blood pressure is the force of blood pushing against the walls of the blood vessels as the heart pumps blood. Normal blood pressure is generally between 90/60 mmHg and 120/80 mmHg. High blood pressure can damage blood vessels and increase the risk of heart disease, stroke and other health problems. High blood pressure is often referred to as a “silent disease”, as it usually presents no symptoms. It is important to monitor it regularly and treat it if necessary.

Results of a study of over 18,000 women and men in Japan

Consuming two or more cups of coffee a day can double the risk of death from cardiovascular disease in people with severe arterial hypertension [160/100 mm Hg (millimeters of mercury) or +], but not in people with arterial hypertension not considered severe.

However, the study found that a cup of coffee and daily consumption of green tea did not increase the risk of death from cardiovascular disease regardless of blood pressure measurement, even though both beverages contain caffeine.

For the record, previous research [4] has shown that drinking a cup of coffee a day can help heart attack survivors (myocardial infarction) by reducing their risk of death after a heart attack, and can prevent heart attacks or strokes in healthy people.

In addition, other studies have suggested that drinking coffee regularly can help improve overall health (reduce the risk of developing chronic diseases and certain cancers, help control appetite, help reduce the risk of depression or increase alertness, etc.).

However, it is not yet clear whether this effect is due to caffeine or to another substance present in coffee. On the harmful side, consuming too much coffee can increase blood pressure and lead to anxiety, heart palpitations and sleep disorders (insomnia).

Data analysis over 19 years of follow-up

The aim of this study was to determine whether the known protective effect of coffee also applies to people with varying degrees of hypertension, and also to examine the effects of green tea in the same population.

Moreover, this is the first study to find an association between the consumption of two or more cups of coffee a day and cardiovascular disease mortality in people with severe hypertension.

Hypertension occurs when the force of blood pushing against blood vessel walls is consistently too high, forcing the heart to work harder to pump blood.

The researchers classified the blood pressure criteria into five categories:

  • optimal and normal (less than 130/85 mm Hg) ;
  • high normal (130-139/85-89 mm Hg) ;
  • grade 1 hypertension (140-159/90-99 mm Hg) ;
  • grade 2 (160-179/100-109 mm Hg) ;
  • grade 3 (greater than 180/110 mm Hg).

Blood pressure measurements at grades 2 and 3 were considered severe hypertension in this study.

At baseline, study participants included more than 12,000 women and 6,570 men, aged 40 to 79. Participants provided data through health examinations and self-administered questionnaires assessing lifestyle, diet and medical history. During nearly 19 years of follow-up, 842 cardiovascular disease-related deaths were documented.

What does analysis of the data from this study reveal?

Analysis of this study’s data on coffee and green tea consumption for all participants revealed that :

  • Drinking two or more cups of coffee a day was associated with twice the risk of death from cardiovascular disease in people whose blood pressure was 160/100 mm Hg or higher, compared with those who did not drink coffee.
  • Drinking one cup of coffee a day was not associated with an increased risk of death from cardiovascular disease in all blood pressure categories.
  • Green tea consumption was not associated with an increased risk of death from cardiovascular disease in all blood pressure categories.

On the other hand, these results may support the assertion that people with severe hypertension should avoid drinking too much coffee.

Indeed, people with severe hypertension are more sensitive to the effects of caffeine, and the harmful effects of caffeine may outweigh any protective effects, and may thus increase the risk of death.

The study found that people who consumed coffee more frequently were more likely to be younger, to smoke tobacco or currently drink alcohol, to eat fewer vegetables, to have higher total cholesterol levels, and to have lower systolic blood pressure, regardless of blood pressure category.

Furthermore, the benefits of green tea may be explained by the presence of polyphenols, which are micronutrients with healthy antioxidant and anti-inflammatory properties found in plants. The researchers noted that polyphenols could partially explain why only coffee consumption was associated with an increased risk of death in people with severe hypertension despite both green tea and coffee containing caffeine.

Finally, even if these results are reliable and will delight green tea lovers (sencha, gyokuro, matcha, long jing, etc.), there are several limitations to this research. Coffee and tea consumption were self-reported; blood pressure was measured at a single time point; and the observational nature of the study did not allow us to establish a direct cause-and-effect relationship between coffee consumption and the risk of cardiovascular disease in people with severe hypertension.

Editorial : Jimmy Braun – Blog Nutrition Santé – Mars 2023

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