Unsweetened coffee associated with reduced risk of Alzheimer’s and Parkinson’s diseases, study finds

Recent research has found that older individuals with a higher intake of caffeinated coffee, particularly the unsweetened variety, are less likely to suffer from Alzheimer’s disease, related dementias, and Parkinson’s disease. This association was not observed for sweetened or artificially sweetened coffee. The research was published in the American Journal of Clinical Nutrition.

Alzheimer’s and Parkinson’s diseases are the most common neurodegenerative disorders and are among the leading causes of disability and dependency in aging populations worldwide. Estimates indicate that these conditions currently affect over 63 million people globally.

Alzheimer’s disease is a progressive neurological disorder that impacts memory, thinking, and behavior, making it the most common cause of dementia. It typically begins with mild memory loss and gradually worsens, interfering with daily life and independence. The disease is characterized by the accumulation of amyloid plaques and tau tangles in the brain, which lead to the death of brain cells. While there is no cure, treatments focus on managing symptoms and improving quality of life.

Parkinson’s disease is a progressive neurological disorder that primarily affects movement due to the degeneration of dopamine-producing neurons in the brain. Common symptoms include tremors, stiffness, slow movement (bradykinesia), and balance difficulties, which worsen over time. Non-motor symptoms, such as sleep disturbances, depression, and cognitive changes, can also occur.

Study author Tingjing Zhang sought to examine the associations between coffee consumption and the risk of neurodegenerative diseases. Unlike previous studies, this research also considered the type of coffee consumed.

The researchers analyzed data from the UK Biobank, a large-scale biomedical database containing health, genetic, and lifestyle information from approximately 500,000 individuals living in the United Kingdom. This resource is available for research analyses to researchers worldwide.

Data for this analysis came from 204,847 UK Biobank participants who completed dietary assessments between 2009 and 2012. Participants were between 40 and 69 years old, and 55% were female.

Coffee consumption data were collected using the Oxford Web-Q, a web-based questionnaire that asked participants to recall the types and amounts of foods and beverages they consumed in the previous 24 hours. Participants completed this questionnaire on five separate occasions over the course of one year, allowing researchers to examine variations in food and beverage intake.

Participants reported the quantity of coffee consumed in the previous 24 hours. Based on their responses, they were categorized into four groups: non-coffee consumers, consumers of unsweetened coffee, consumers of sugar-sweetened coffee, and consumers of artificially sweetened coffee. Participants who reported coffee intake in at least one dietary recall were categorized as coffee consumers, while those who did not were classified as non-coffee consumers. Those who consistently consumed the same type of coffee across different recalls were identified as sole consumers, while others were categorized as overlapping consumers and excluded from the analysis.

Results showed that approximately 54% of participants consumed unsweetened coffee, while 24% did not drink coffee at all. Sugar-sweetened coffee was consumed by 16% of participants, and the remaining 7% drank artificially sweetened coffee. Participants who did not drink coffee generally preferred tea.

Those who consumed more unsweetened coffee had a 29–30% lower risk of Alzheimer’s disease, related dementias, and Parkinson’s disease, as well as a 43% lower risk of dying from these conditions, compared to non-coffee drinkers. In contrast, consumption of sweetened or artificially sweetened coffee was not associated with a reduced risk of these diseases or related mortality.

Further analysis by caffeine content revealed that drinking decaffeinated coffee was associated with a 34–37% lower risk of Alzheimer’s and Parkinson’s diseases and a 47% lower risk of related mortality, compared to non-coffee drinkers. These associations were absent among consumers of sweetened or artificially sweetened decaffeinated coffee.

“Our study reveals significant negative associations of the consumption of unsweetened caffeinated coffee with the risk of ADRD and PD [Alzheimer’s disease and related dementias and Parkinson’s disease], as well as related mortality. This underscores an important public health message: the addition of sugar or artificial sweeteners to coffee may have harmful effects and should be approached cautiously. Instead, the recommendation leans toward the consumption of unsweetened and caffeinated coffee,” the study authors concluded.

While the study sheds light on the links between coffee consumption and neurodegenerative diseases, its design does not allow for causal inferences. It remains unclear whether coffee consumption reduces the risk of these diseases, whether these diseases (or their early symptoms) influence beverage intake habits, or if a third factor affects both disease risk and beverage consumption.

The paper, “Associations between different coffee types, neurodegenerative diseases, and related mortality: findings from a large prospective cohort study,” was authored by Tingjing Zhang, Jiangen Song, Zhenfei Shen, Kewan Yin, Feifei Yang, Honghao Yang, Zheng Ma, Liangkai Chen, Yanhui Lu, and Yang Xia.