Green Tea and Coffee Benefits for Diabetes

Study finds green tea and coffee may offer significant health benefits in people with diabetes, particularly when both are consumed.   

According to the online journal BMJ Open Diabetes Research and Care, drinking plenty of green tea and coffee in combination could lower the risk of dying from any cause among patients with type 2 diabetes. The study showed that drinking at least 4 cups of green tea in addition to at least 2 cups of coffee resulted in a 63 percent lower risk of death for approximately five years. Patients with type 2 diabetes are more likely to develop circulatory diseases, dementia, cancer, and bone fractures; although there is an increase in effective drugs, lifestyle modifications like exercise and diet are the most critical treatment forms.  Some researchers suggest that consistent drinking of green tea and coffee is vital for health due to the various bioactive compounds each of these beverages contains.  Out of all these studies, none have been performed with patients with type 2 diabetes. The researchers decided to investigate the potential benefit of green tea and coffee when used separately and together in reducing the risk of death among people with type 2 diabetes.   

The observational study ran an average of 5 years and had 4,923 Japanese patients, 2,790 men and 2,133 women.  All of the patients were diagnosed with type 2 diabetes, with an average age of 66.  All of the patients had previously been enrolled in The Fukuoka Diabetes Registry, a multicenter prospective study looking at the effect of drug treatments and lifestyle on the lifespan of patients with type 2 diabetes.  Each patient had to fill out a 58 item food and drink questionnaire daily.  The questionnaire consisted of how much green tea and coffee they drank.  Each patient also provided essential background information on their lifestyle factors, such as smoking, exercising, regular exercise, and the amount of sleep they received each night.  The researchers measured each patient’s height, weight, and blood pressure as well as their blood and urine samples to ensure there were no other underlying risk factors.  Six hundred seven of the participants did not drink green tea at all, 1,143 drank at least 1 cup a day, 1,384 drank 2 to 3 cups a day, and 1,784 drank at least 4 cups daily.  Nearly 1,000 (994) of the participants did not drink any coffee, 1,306 drank at least 1 cup daily, 963 drank up to 2 cups every day, and 1,660 drank two more cups daily.  During the trial period, 309 participants died, 218 men and 91 women.  The study reported that death’s leading causes were cancer (114) and cardiovascular disease (76).  When compared to the patients who did not drink green tea or coffee, those who consumed one or both had a lower chance of dying from any cause. The lowest chance was associated with drinking higher amounts of green tea and coffee in combination.   

The study showed that drinking at least 1 cup of green tea every day was linked with a 15 percent lower chance of death, while those who drank 2 to 3 cups were associated with a 27 percent lower event of death.  Patients who drank at least 4 cups daily were linked with 40 percent lower odds.  The group of coffee drinkers who drank up to 1 cup daily was linked to 12 percent lower odds, while 1 cup was associated with 19 percent lower odds, and patients who drank two or more cups were associated with 41 percent lower odds.  The overall risk of death was lower in patients who drank green tea and coffee at the same time daily.  Patients who drank 2 to 3 cups of green tea and two or more coffee cups were at a reduction of 51 percent.  Patients who drank four or more cups of green tea plus 1 cup of coffee daily were at a decrease of 58 percent.  Patients who drank four or more cups of green tea and two or more cups of coffee daily were at a reduction of 63 percent. 

In conclusion, the observational study cannot establish a cause.  The researchers noticed limitations, such as the green tea available in Japan may not be available worldwide.  Green tea in Japan contained antioxidants and anti-inflammatory compounds, including phenols and theanine, and their caffeine. Coffee also included numerous bioactive components.  Even though caffeine is harmful to the circulatory system, caffeine is thought to alter insulin production and sensitivity.   

Practice Pearls: 

• The greater the consumption of green tea and coffee together, the greater the associated reduction in all-cause mortality.   
• Caffeine must be monitored in type 2 diabetes due to the possible effect on the circulatory system.   
• The benefit is seen in tea and coffee containing phenols and theanine.  

Additive effects of green tea and coffee on all-cause mortality in patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry, BMJ Open Diabetes Research & Care,  

Science X. “Drinking Green Tea and Coffee Daily Linked to Lower Death Risk in People with Diabetes.“ Medical Xpress – Medical Research Advances and Health News,  

A‘Kira Shavers, PharmD Candidate 2021, South College School of Pharmacy