A new prospective cohort study published in the online journal, BMJ Open Diabetes Research & Care has found that drinking four or more daily cups of green tea and two cups of coffee is linked to 65% lower of death from any cause among people with type 2 diabetes (T2DM).
While previous research has found that regularly drinking green tea and coffee may be beneficial for health because of the various bioactive compounds these beverages contain, few of these studies have been carried out in people with diabetes – until now.
Researchers in the latest study tracked the health of 4923 Japanese people enrolled in The Fukuoka Diabetes Registry (2790 men and 2133 women) with T2DM (average age 66 years) for an average of just over five years.
Comparing those who drank neither green tea or coffee with those who drank one or both the study authors found that green tea and coffee drinkers had lower odds of dying from any cause, with the lowest odds associated with drinking higher quantities of both green tea and coffee.
Furthermore, they found that drinking up to one cup of green tea every day was associated with 15% lower odds of death; while drinking two to three cups was associated with 27% lower odds.
Getting through 4 or more daily cups was associated with 40% lower odds.
Among coffee drinkers, up to one daily cup was associated with 12% lower odds of dying. Two or more cups was associated with 41% lower odds.
The risk of death was even lower for those who drank both green tea and coffee every day:
- 51% lower for 2-3 cups of green tea plus 2 or more of coffee.
- 58% lower for 4 or more cups of green tea plus 1 cup of coffee every day.
- 63% lower for a combination of 4 or more cups of green tea and 2 or more cups of coffee every day.
Study limitations
Despite the promising results, the authors warn of several study limitations, including the following:
- It’s an observational study, therefore, can’t establish cause.
- The study relied on subjective assessments of the quantities of green tea and coffee drunk (participants filled out a 58-iten food and drink questionnaire).
- No information was gathered on other potentially influential factors, such as household income and educational attainment.
The study authors also add that the green tea available in Japan may not be the same as that found elsewhere.
Possible reasons for the findings
The biology behind these observations isn’t fully understood, explain the researchers.
Green tea contains several antioxidant and anti-inflammatory compounds, including phenols and theanine, as well as caffeine.
Coffee also contains numerous bioactive components, including phenols. As well as its potentially harmful effects on the circulatory system, caffeine is thought to alter insulin production and sensitivity.
“This prospective cohort study demonstrated that greater consumption of green tea and coffee was significantly associated with reduced all-cause mortality: the effects may be additive,” the researchers conclude.
To read the study, visit: drc.bmj.com/content/8/1/e001252.full
