After my Upshot column on the potential health benefits of coffee, the No. 1 request I got was to look into the potential benefits — or harms — of tea.
Unlike coffee, tea does not seem to generate negative perceptions. I know many more people who think that tea is beneficial, much more so than coffee. (That is, until my coffee column, I hope.)
As with coffee, a fairly large number of studies have looked at associations between tea and health. Most of the studies don’t have the rigor of randomized control trials and don’t prove causality. But so many studies were available that I was able to focus on systematic reviews and meta-analyses, or “studies of studies.”
Nine prospective cohort studies, three retrospective cohort studies and four cross-sectional studies including more than 800,000 participants have looked at the association between tea and liver disease. Those who drank tea were less likely to have hepatocellular carcinoma, liver steatosis, liver cirrhosis and chronic liver disease. This confirmed the findings in a previous systematic review published in 2008.
Tea has been associated with a lower risk of depression. A 2015 meta-analysis of 11 studies with almost 23,000 participants found that for every three cups of tea consumed per day, the relative risk of depression decreased 37 percent.
Tea was also associated with a reduction in the risk of stroke, with those consuming at least three cups a day having a 21 percent lower risk than those consuming less than a cup a day. A more recent meta-analysis examined 22 prospective studies on more than 850,000 people and found that drinking an additional three cups of tea a day was associated with a reduction in coronary heart disease (27 percent), cardiac death (26 percent), stroke (18 percent), total mortality (24 percent), cerebral infarction (16 percent) and intracerebral hemorrhage (21 percent).