Green Tea & Coffee Consumption May Benefit Type-2 Diabetics


Prior research has established that the consumption of green tea or coffee has been said to reduce the all-cause mortality in the general public. However, as to the similar effects in those with health challenges, such as diabetes, research is either controversial or devoid – until now.

Japanese researchers publishing the Additive Effects of Green Tea and Coffee on All-Cause Mortality in Patients with Type-2 Diabetes Mellitus: the Fukuoka Diabetes Registry, which appeared in October 2020 in the open-access online BMJ (British Medical Journal) Diabetes Research & Care, determined that, “higher consumption of green tea and coffee was associated with reduced all-cause mortality: their combined effect appeared to be additive in patients with type-2 diabetes.”

The Japanese researchers from the Departments of Medicine and Clinical Sciences, Graduate School of Medical Sciences and the Division of Internal Medicine, Fukuoka, Japan, comment that green tea derives benefits from fresh leaves of Camellia sinensis – containing various chemicals, such as phenolic compounds, theanine, and caffeine, which possess antioxidant, anti-inflammatory, or anti-bacterial properties.

Coffee, note the Japanese, contains phenolic compounds and caffeine that offer antioxidant, anti-inflammatory, and ant-mutagenic benefits – especially to type-2 diabetics, those with abnormal lipid profiles, and malignancy.

To reach this conclusion, the investigators, after appropriate exclusion criteria, used data from 4923 study participants enrolled between April 2008 and October 2010, in the Fukuoka Diabetes Registry, “a multicenter prospective study designed to investigate the effects of modern treatments and lifestyle on the prognoses of patients with diabetes mellitus.”

Using a self-administered questionnaire, the participants provided information regarding their diagnosed diabetes duration, smoking habits, alcohol intake, leisure-time physical activity, sleep duration, depressive symptoms, and history of coronary heart disease, stroke, and cancer. Their smoking habits and alcohol intake were classified as either current or not.

Body weight, height and body mass index were ascertained – along with blood pressure. Medical charts were reviewed for all medications, including insulin, oral hypoglycemic agent, antihypertensive drugs, antiplatelet drugs, and statins. The Japanese commented that using self-reported answers to dietary questions, “we categorized the participants into the following four groups by beverage: green tea, none, ≤1 cup/day, 2–3 cups /day, ≥4 cups/day; and coffee, none, <1 cup/day, 1 cup/day, ≥2 cups/day. There were no questions about the consumption of
decaffeinated or caffeinated drinks because decaffeinated beverages are uncommon in Japan.”

From a laboratory perspective, blood samples and spot urine samples were obtained. Hemoglobin A1c (HbA1c) was determined by high-performance liquid chromatograph. Serum low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, creatinine, and urinary creatinine, and albumin were measured – with the glomerular filtration rate (GFR) and calculations of the urinary albumin-creatinine ratio levels.

It was concluded that, “our results suggest that consuming green tea and coffee may have beneficial effects on the longevity of Japanese people with type 2 diabetes.” How this data translates to all of us outside Japan, will require further research.

Until then, keep my green tea and black coffee consumption – in moderation – flowing.

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