How much green tea participants drank, and whether they drank it daily, mattered in a study of older adults with Parkinson's disease. Those drinking a high amount daily were less likely to have certain non-motor symptoms than those drinking less. Additionally, daily drinkers needed fewer medications compared with non-daily drinkers.

"Non-motor symptoms are prominent features of advanced Parkinson's disease that contribute to disability severity and quality of life impairment," authors Harutoshi Sakakima of Kagoshima University in Japan and colleagues noted.

Among green tea drinkers who consumed more than a liter of green tea per day, a significantly lower proportion had moderate and severe sleep disturbances in comparison with green tea drinkers who consumed lesser amounts. Another non-motor symptom, constipation, was reduced in association with daily green tea intake. Parkinson's disease patients who consumed green tea daily needed significantly fewer medications than individuals who consumed the beverage less often.

"Lifestyle habits, including tea and coffee consumption, have been associated with a reduced risk of developing Parkinson's disease in some epidemiological studies," Sakakima and colleagues wrote. "Experimental studies have shown that polyphenols in tea (those from green tea in particular), including catechin and its derivatives, may exert potent neuroprotective activities that can ameliorate neurodegenerative disease symptoms such as those in Parkinson's disease."

The study included 105 older men and women residing in Japan who were diagnosed with Parkinson's disease. Seventy-eight individuals reported drinking green tea daily, 22 people were non-daily green tea drinkers, and five individuals did not consume green tea. Daily green tea drinkers were analyzed according to whether they consumed less than 0.5 liters, 0.5 to one liter or greater than one liter per day. The findings were reported September 30, 2026, in Nutrition and Health.¹