Numerous prospective studies consistently show that moderate coffee consumption is associated with a reduced risk of type 2 diabetes, cardiovascular disease, and all-cause mortality. For this reason, coffee was included in the 2015–2020 Dietary Guidelines for Americans as an important component of a healthy dietary pattern. However, existing evidence remains controversial regarding the association between high coffee intake (more than 3–5 cups per day) and mortality risk.
In recent years, accumulating evidence indicates that circadian rhythms play a key role in regulating human eating behavior and metabolic homeostasis, and previous studies suggest that meal timing itself may significantly modify the relationship between food intake and health outcomes. Given that caffeine exerts a marked stimulatory effect on the central nervous system, drinking coffee in the evening may disrupt circadian rhythms, thereby influencing the association between coffee consumption and health risks.
Nevertheless, it remains unclear whether stable coffee-drinking timing patterns exist in the general population and whether these patterns are related to mortality risk. Against this background, the present study used data from the U.S. National Health and Nutrition Examination Survey (NHANES) to identify coffee-drinking timing patterns through cluster analysis, and validated the findings in the Lifestyle Study of Women and Men (WLVS and MLVS), which are sub-cohorts of the Nurses’ Health Study (NHS), Nurses’ Health Study II (NHS II), and Health Professionals Follow-up Study (HPFS). It further systematically evaluated the combined associations of coffee-drinking timing patterns and intake volume with all-cause and cause-specific mortality risks.
This study provides a new interpretive framework for the long-standing controversy over the safety of high-dose coffee consumption. Inconsistent conclusions about high intake in previous studies may stem not from dosage itself, but from differences in drinking time. When coffee was consumed mainly in the early morning, even more than 3 cups per day was associated with a significantly lower mortality risk; whereas when coffee intake was spread throughout the day, its potential protective effects nearly disappeared. This finding offers a unified logic for explaining inconsistent results across cohort studies regarding heavy coffee drinking.
From a public health and clinical nutrition perspective, this study is the first to systematically incorporate meal timing into the core rationale linking coffee and health, suggesting that future dietary intervention strategies should be restructured around a three-dimensional framework: what to eat, how much to eat, and when to eat. For the general population, the research provides a simple and practically meaningful health strategy: concentrating coffee consumption in the early morning, rather than spreading it across the day, may be more beneficial than cutting back by one cup.