Researchers studied nearly 5,000 patients over a five-year period and found that drinking either beverage alone helped reduce the risk of mortality (from any cause): Drinking one cup of green tea per day was associated with a 15% lower risk of death compared to those who did not drink green tea. 27% reduction in mortality risk was associated with drinking two to three cups and a 40% reduction in mortality risk was associated with drinking four or more cups of green tea. Those who drank one cup of coffee daily had a 12% lower mortality risk and two or more cups was associated with a 41% mortality risk reduction compared to those who drank no coffee.
But even more benefit came from participants who drank both green tea and coffee daily. Two to three cups of green tea and two or more cups of coffee were associated with a 51% reduction in mortality risk; four or more cups of green tea plus one cup of coffee daily was associated with a 58% lower mortality risk; and four or more cups of green tea and two or more cups of coffee daily was associated with a 63% lower mortality risk. Those are head-turning numbers.
While the authors did not determine the mechanisms of action, green tea and coffee contain antioxidant and anti-inflammatory compounds, including methylation adaptogens such as quercetin, chlorogenic acid, catechins, apigenin, luteolin, myricetin, kaempferol, and myricetin. These substances have been shown to affect epigenetic expression, including DNA methylation and have been shown to improve insulin resistance, vascular function, and inflammation. It’s plausible that these mechanisms may be at work here, and we certainly have good data on the protective effects of green tea from other sources and use it regularly for various indications.
Some note of caution: High caffeine intake can be a problem for many people, leading to side effects such as anxiety, stomach upset, insomnia, headaches, dehydration, shakiness, and heart palpitations. If this is you, then this kind of intervention isn’t recommended. Coffee in the context of green tea seems to improve its benefits, but should still be consumed in moderation. Remember, this study wasn’t conducted in a general healthy population – it looked specifically at those with type 2 diabetes.