A study involving more than 46,000 American adults found that drinking black coffee or coffee with minimal additives was associated with a 14% lower risk of death, while beverages containing larger amounts of sugar and saturated fat showed no comparable benefit.
By yourNEWS Media Newsroom
The ingredients added to a daily cup of coffee may influence whether the beverage is associated with a longer life, according to research from Tufts University examining the dietary habits and mortality records of more than 46,000 American adults. Investigators found that people who consumed black coffee or coffee containing small amounts of added sugar and saturated fat had a significantly lower risk of death from all causes than those who did not drink coffee, while the same association was not established among participants who regularly consumed heavily sweetened or cream-enriched varieties.
The findings, published in July 2025 in The Journal of Nutrition, suggest that the relationship between coffee consumption and longevity may depend partly on how the beverage is prepared. The researchers identified a 14% lower risk of all-cause mortality among people who drank black coffee or coffee with limited additives, with the broader analysis showing a 17% reduction among those consuming approximately two to three cups daily.
The Tufts University investigation examined whether ingredients commonly added to coffee could alter the favorable mortality associations reported in earlier population studies. The research distinguished between unsweetened coffee and beverages containing different quantities of sugar and saturated fat, rather than treating all coffee consumption as nutritionally equivalent.
The distinction is significant because coffee is consumed by millions of Americans each day, often with ingredients that substantially change its calorie content and nutritional composition. While an ordinary cup of black coffee contains very few calories, sweetened coffee drinks can include substantial amounts of sugar, cream, flavored syrup and other additives.
Researchers led by Bingjie Zhou of the Friedman School of Nutrition Science and Policy at Tufts University analyzed information from 46,222 adults aged 20 and older who participated in the National Health and Nutrition Examination Survey between 1999 and 2018. The investigators linked participants’ dietary records to the National Death Index to determine whether coffee consumption was associated with differences in mortality over subsequent years.
The study included nine consecutive survey cycles and examined deaths from all causes, cardiovascular disease and cancer. Researchers evaluated coffee intake by quantity, caffeine content and the amounts of added sugar and saturated fat in each serving. The analysis accounted for demographic characteristics, lifestyle factors and other variables that could influence mortality.
During a median follow-up ranging from approximately nine to 11 years, 7,074 participants died. Those deaths included 1,176 attributed to cancer and 1,089 associated with cardiovascular disease, providing investigators with a substantial body of information for assessing possible relationships between coffee consumption and long-term health outcomes.
The results indicated that drinking at least one cup of coffee daily was associated with a 16% lower risk of death from all causes compared with not drinking coffee. Among people consuming two to three cups per day, the association increased to approximately 17%. Drinking more than three cups did not produce additional reductions, suggesting that higher consumption was not necessarily associated with greater benefits.
When researchers examined coffee preparation, the most consistent associations appeared among people drinking black coffee or coffee containing relatively small amounts of added sugar and saturated fat. In the published study, titled “Coffee Consumption and Mortality among United States Adults: A Prospective Cohort Study,” the investigators concluded that the favorable relationship between coffee and mortality may diminish when larger quantities of those ingredients are added.
The findings do not establish that coffee prevents premature death or that adding cream and sugar directly causes earlier mortality. The research was observational, meaning investigators identified statistical relationships rather than conducting a controlled experiment in which participants were randomly assigned different coffee preparations over many years.
Nevertheless, the results provide additional evidence that the nutritional characteristics of a beverage can matter when evaluating its potential health effects.
Fang Fang Zhang, the study’s senior author and Neely Family Professor at the Friedman School, said researchers were particularly interested in whether coffee’s naturally occurring compounds could help explain findings from earlier studies.
“Coffee is among the most-consumed beverages in the world, and with nearly half of American adults reporting drinking at least one cup per day, it’s important for us to know what it might mean for health,” Zhang said.
“The health benefits of coffee might be attributable to its bioactive compounds, but our results suggest that the addition of sugar and saturated fat may reduce the mortality benefits.”
The researchers established specific thresholds to distinguish relatively small additions from larger quantities. Coffee was classified as low in added sugar when an 8-ounce serving contained less than 2.5 grams, approximately half a teaspoon. Added sugar included granulated sugar, honey and syrup.
The threshold represented less than 5% of the daily value for added sugar. Coffee was considered low in saturated fat when an 8-ounce serving contained less than 1 gram, approximately the amount supplied by one tablespoon of half-and-half or light cream, or five tablespoons of 2% milk.
These measurements allowed the researchers to distinguish an ordinary cup of coffee containing a modest amount of milk or sugar from beverages prepared with larger quantities of sweeteners and cream.
The researchers found that the mortality association was less apparent when the amounts of added sugar or saturated fat exceeded the study’s designated thresholds. Coffee containing both higher sugar and higher saturated fat levels did not demonstrate the same statistically significant reduction in mortality observed among black coffee drinkers.
That absence of a significant association does not mean researchers proved such drinks cancel all potential coffee benefits. It means the study did not establish a comparable mortality advantage for those categories after accounting for the variables included in its statistical analysis.
Zhou said the findings support broader dietary recommendations to moderate ingredients that can increase sugar and saturated fat consumption.
“Our results align with the Dietary Guidelines for Americans which recommend limiting added sugar and saturated fat,” Zhou said.
The analysis also identified differences between caffeinated and decaffeinated coffee. Associations between coffee consumption and lower mortality were more consistently observed for caffeinated varieties, while researchers did not establish a statistically significant association for decaffeinated coffee.
However, the investigators cautioned against interpreting that finding as proof that decaffeinated coffee lacks health benefits. Relatively few participants regularly consumed decaffeinated coffee, limiting the statistical power available to detect differences.
The relationship between coffee and cardiovascular mortality was also more complicated than the findings for deaths from all causes. Moderate coffee consumption was associated with lower cardiovascular mortality in some categories, but the relationship weakened at higher intake levels. Researchers found no significant overall association between coffee drinking and mortality specifically attributed to cancer.
Those distinctions suggest that coffee may relate differently to various health outcomes, rather than producing a uniform reduction across every major cause of death.
The Tufts findings are consistent with a substantial body of nutritional research examining coffee consumption, although some earlier studies reached different conclusions about the effects of sugar.
A 2022 investigation involving 171,616 participants in the United Kingdom Biobank found that moderate consumption of both unsweetened and lightly sweetened coffee was associated with lower mortality compared with abstaining from coffee.
Published in Annals of Internal Medicine, that research followed participants for a median of seven years. All participants were free of cardiovascular disease and cancer at the beginning of the study, allowing investigators to examine subsequent health outcomes among people with different coffee-drinking habits.
The researchers recorded 3,177 deaths, including 1,725 from cancer and 628 from cardiovascular disease. They found that participants drinking moderate quantities of unsweetened coffee generally had lower mortality rates than those who did not consume coffee.
For example, people drinking approximately two and a half to three and a half cups of unsweetened coffee daily had an estimated 29% lower risk of death during follow-up. Similar associations appeared among some groups consuming coffee with modest amounts of sugar.
The results differed from the interpretation that any addition of sugar necessarily eliminates coffee’s potential advantages. Instead, they suggested that quantity matters and that small amounts of sweetener may not produce the same effects as larger additions.
Investigators also examined coffee prepared with artificial sweeteners but found less consistent relationships, leaving uncertainty about whether those substitutes produce comparable health outcomes.
Both the American and British studies relied on self-reported dietary information. Participants described their consumption habits, and researchers analyzed subsequent medical outcomes. Such methods are valuable for identifying patterns in large populations, but they cannot establish that the beverage itself caused differences in survival.
People who drink black coffee may differ from those who favor heavily sweetened varieties in other important ways, including overall diet quality, physical activity, smoking habits, income and existing medical conditions. Statistical adjustments can account for some of those differences, but they cannot eliminate every potential source of bias.
The Tufts study also relied heavily on dietary recall information collected over a limited period. Because individuals may change their coffee habits over time, a survey describing what someone consumed on a particular day may not fully represent their long-term exposure.
Other investigations have expanded the analysis beyond coffee alone, examining whether different combinations of beverages are associated with longevity.
A study involving 182,770 adults in the United Kingdom Biobank found that a daily combination of coffee, tea and water was associated with lower mortality over approximately 13 years of follow-up. Researchers identified especially favorable associations among participants consuming roughly seven to eight beverages daily, with a combination of approximately two cups of coffee and three cups of tea receiving particular attention.
The research examining coffee, tea and water consumption reported an association with as much as a 45% lower risk of death from all causes among certain consumption patterns. The findings also suggested a relationship between particular beverage combinations and reduced cancer mortality.
Those results should not be interpreted as proof that following an exact beverage ratio will extend life. They reflect statistical comparisons among people with different consumption habits, and individuals may have differed in numerous other characteristics associated with health.
Separate large-scale research has also linked coffee and tea consumption to favorable cardiovascular outcomes. In one study examining nearly 450,000 UK Biobank participants, investigators found associations between moderate consumption of ground, instant and decaffeinated coffee and reduced risks of cardiovascular disease and death.
Such findings have encouraged scientists to investigate whether specific compounds in coffee contribute to biological processes involved in inflammation, metabolism and cellular protection.
Coffee contains hundreds of naturally occurring substances, including caffeine, chlorogenic acids and other polyphenols. These compounds have attracted scientific attention because laboratory and observational studies suggest they may influence oxidative stress, glucose regulation, inflammatory signaling and vascular function.
Polyphenols are particularly important to current research because they are present in numerous plant foods and beverages, including coffee, tea, berries, cocoa and certain vegetables. Some have demonstrated antioxidant and anti-inflammatory activity in experimental settings, although their effects in the human body depend on absorption, metabolism and consumption patterns.
Coffee also contains substances that may influence the activity of enzymes and signaling pathways involved in energy regulation. One frequently studied pathway involves adenosine monophosphate-activated protein kinase, known as AMPK, which helps cells respond to changes in energy availability.
Experimental research has investigated whether caffeine can influence AMPK signaling and cellular stress responses. Laboratory studies involving yeast and other organisms have reported changes in longevity-related processes under certain conditions, but those findings cannot be directly translated into predictions about human lifespan.
Some laboratory experiments have suggested that caffeine exposure may extend yeast lifespan by approximately 10% to 20%. However, yeast biology differs substantially from human physiology, and researchers have not established that drinking coffee activates the same processes strongly enough to extend human life.
The hypothesis that coffee’s natural compounds may have beneficial effects also does not establish that sugar or saturated fat directly neutralizes those compounds. Higher intake of added sugar and saturated fat may be associated with different dietary and metabolic conditions, but determining whether they specifically alter coffee’s biological activity requires further controlled research.
Other investigations have focused on possible benefits beyond mortality. Coffee consumption has been associated in some studies with a lower incidence of Parkinson’s disease, certain liver conditions and cardiovascular disorders, although results vary according to study design, population and consumption level.
Researchers have also investigated whether regular coffee consumption is associated with physical function in older adults. A prospective study involving 12,583 adults in Singapore examined relationships between coffee drinking and frailty, a condition involving reduced strength, endurance and resilience that can increase vulnerability to illness and disability.
The findings contributed to broader interest in whether coffee consumption may be associated with healthier aging, although observational associations cannot establish that drinking coffee directly prevents frailty.
Another emerging area involves the relationship between coffee and the gut-brain axis, the network of interactions linking intestinal microorganisms, immune activity and the nervous system.
Researchers have examined whether compounds present in both caffeinated and decaffeinated coffee influence intestinal bacteria and biological pathways associated with mood, stress and neurological function.
Dr. John Cryan, a principal investigator at APC Microbiome Ireland, has participated in research exploring the gut-brain axis and the ways dietary compounds may affect communication between the digestive system and brain. Such investigations suggest that caffeine may not be the only component responsible for coffee’s potential physiological effects.
Still, evidence regarding coffee, the microbiome and emotional well-being remains preliminary. Changes in bacterial populations or laboratory measurements do not automatically establish improvements in mental health or long-term disease prevention.
The broader evidence also demonstrates that coffee is not equally appropriate for everyone. Caffeine sensitivity differs considerably among individuals, and excessive intake can cause nervousness, palpitations, gastrointestinal discomfort and disturbed sleep.
Health authorities generally advise most healthy adults to limit caffeine to approximately 400 milligrams daily, although some individuals experience adverse effects at substantially lower amounts. Pregnant women and people with certain medical conditions may need different limits.
Coffee preparation can also affect its nutritional characteristics. A plain brewed cup contains very few calories, but additions such as sweetened creamers, flavored syrups and whipped toppings can turn a low-calorie beverage into one containing significant quantities of added sugar and saturated fat.
For people who prefer a different flavor without large amounts of sweetener, nutrition specialists sometimes suggest cinnamon or unsweetened cocoa powder. Others recommend reducing sugar gradually or using modest quantities of milk rather than heavily sweetened creamers.
These suggestions concern the overall nutritional composition of the beverage rather than proven longevity benefits from any particular ingredient. Claims that specialty beans, organic products or specific flavor additions can independently extend lifespan require stronger clinical evidence.
The scientific distinction between ordinary coffee and heavily modified coffee drinks remains relevant because the amounts of sugar and saturated fat considered low in the Tufts study were relatively small. Half a teaspoon of sugar per 8-ounce cup is substantially less than the quantities found in many commercially prepared specialty beverages.
A large flavored coffee can contain several servings of added sugar, depending on its size and ingredients. Consuming those beverages regularly may therefore contribute meaningfully to total daily sugar and calorie intake, independently of any beneficial compounds supplied by the coffee itself.
The Tufts findings should also be considered alongside other research reporting somewhat different results. A previous American cohort analysis found that adding milk or cream, with or without sweetener, did not significantly change the observed association between coffee consumption and mortality. Differences in study populations, ingredient classifications and dietary measurements may help explain the inconsistent findings.
For that reason, the available evidence does not support a definitive conclusion that every amount of cream or sugar eliminates coffee’s potential health advantages.
What the research more consistently suggests is that moderate coffee consumption can be compatible with a healthy dietary pattern and that the nutritional effects of added ingredients should be considered separately.
The Tufts investigators emphasized that their research was designed to examine associations rather than establish clinical recommendations requiring people to begin drinking coffee. The study did not demonstrate that nondrinkers would live longer if they adopted the habit, nor did it prove that individuals could reduce their mortality risk by changing only their coffee preparation.
Nevertheless, the analysis offers additional information for people who already drink coffee and want to understand how their preferred additions may affect the beverage’s nutritional profile.
With more than 46,000 American adults included in the analysis and thousands of recorded deaths during follow-up, the findings strengthen the evidence that coffee consumption and mortality are related in ways that merit further investigation. The results also indicate that researchers should account for added ingredients when evaluating coffee rather than treating every preparation as equivalent.
The central conclusion remains qualified but significant: Black coffee and coffee containing modest quantities of sugar and saturated fat were associated with lower mortality in this American population, while heavily sweetened and cream-enriched preparations did not show the same statistically significant relationship. Whether those differences reflect direct biological effects, other dietary habits or a combination of factors remains unresolved, requiring further research before any causal benefit can be established.
Explainer Infographic
Comments