Coffee does more than just wake you up in the morning—the bitter beverage has been linked to a reduced risk of type 2 diabetes, heart disease, and death. But depending on what you add to your coffee, you might not be reaping these health benefits from your cup of joe, a new study suggests.
Researchers found that people who drank one to two cups of coffee daily had a 14% lower risk of mortality compared to non-coffee drinkers.
However, that was only true for those who took their coffee black, or with small amounts of cream, milk, or sweeteners. Too many additives appeared to undermine coffee’s health benefits.
“If we add a lot of sugars or saturated fat to our diet, that increase[s] our total [caloric] intake, which could also be linked to adverse health outcomes,” said senior study author Fang Fang Zhang, MD, PhD, professor at the Tufts University Friedman School of Nutrition Science and Policy.
For this study, published in May in The Journal of Nutrition, Zhang and her colleagues followed more than 46,000 U.S. adults over the course of about 10 years. The goal was to see whether mortality risk was connected to participants’ coffee drinking habits.
At the start of the study, researchers gave participants a 24-hour diet questionnaire. Based on that information, the researchers estimated participants’ average coffee consumption and noted whether they added sweeteners or products with saturated fat to their coffee.
After tracking participants’ health—including recorded deaths from cancer, cardiovascular disease, and all causes—Zhang and her team found:
- Drinking one cup of coffee each day was linked to a 16% lower all-cause mortality risk
- Drinking two or three daily cups of coffee cut all-cause mortality risk by 17%
Coffee drinkers also had a 29–33% lower risk of heart disease mortality, in particular.
When looking at coffee additives specifically, the researchers found that, compared to non-coffee drinkers, participants had a 14% lower risk of overall mortality if they drank black coffee or coffee low in added sugar and saturated fat.
The research team defined “low added sugar” and “low saturated fat” as any amount below 5% of the recommended daily value. For an 8-ounce brew, this translates to:
- 2.5 grams of sugar, or about a one-third or one-half teaspoon of sugar, syrup, or honey
- 1 gram of fat, or about 5 tablespoons of 2% milk, 1 tablespoon of light cream, or 1 tablespoon of half-and-half
There was no mortality boost for people who took their coffee with more sugar or with a heavy dose of milk or creamer.
Interestingly, data also showed no link between coffee drinking in general and reduced cancer mortality. This might be because the participant pool was on the smaller side, and the researchers didn’t look at associations with any specific cancers, Mingyang Song, ScD, associate professor of clinical epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, told Health.
In his own research, Song has found that patients with colorectal cancer who drank coffee had a higher survival rate, and other experts have shown that coffee can reduce colorectal cancer risk. Overall, though, the evidence for other cancers is mixed.
Because Zhang and the researchers controlled for various demographic factors, Zhang told Health that she’s confident the data suggests a causal relationship between coffee additives (or lack thereof) and lower mortality risk.
However, the study does have some limitations.
Though the data was “informative,” the study’s sample size was limited, making it difficult to understand whether this link might hold up across race or ethnicity, Lu Qi, MD, PhD, professor and director of the Obesity Research Center at Tulane University, told Health.
Additionally, most of people in the study drank their coffee black—there may not have been enough participants drinking their coffee with additives to paint a full picture of how that might affect mortality, added Marilyn Cornelis, PhD, a coffee researcher and associate professor of preventive medicine at the Northwestern University Feinberg School of Medicine.
There are a lot of unknowns about the participants’ actual coffee drinking, too. Habits were only assessed once or twice for each study participant, and “people’s coffee intake may vary day by day,” said Song. “Some people may consume more coffee during weekdays.”
Participants’ coffee consumption may not have been stable over the course of the study, either.
Researchers also didn’t take every type of coffee or additive into account. The specific brew people were drinking may have affected the results, as previous research found that unfiltered coffee doesn’t reduce mortality risk. Plus, the study didn’t look at specific types of sweeteners—for example, sugar vs. low-calorie alternatives—or compare dairy to non-dairy products.
Each cup of coffee is loaded with over 100 different molecules and metabolites—one group of these, polyphenols, may be largely responsible for the many health benefits associated with coffee.
Polyphenols are antioxidants, meaning they help reduce inflammation and eliminate free radicals that would otherwise damage the body’s cells.
So this relationship between coffee consumption and lower mortality risk “is a biologically plausible” one, James O’Keefe, MD, cardiologist at St. Luke’s Mid America Heart Institute, told Health. “Coffee is the top source of antioxidants in the American diet.”
Adding more sugar or saturated fats to your coffee doesn’t necessarily get rid of polyphenols or cancel out their effects, Song explained. Rather, high consumption of sugar and saturated fats in general are simply linked to worse cardiovascular health outcomes and higher mortality.
Since this is the first study to look at the effects of coffee additives on mortality risk, the evidence isn’t yet strong enough to make definitive recommendations about the healthiest way to drink coffee, Song said.
As a general rule of thumb, though, “it’s always wise to reduce the consumption of sugar and saturated fat,” he said.
Still, if you like adding a little cream and sweetener to your coffee in the mornings, there’s no need to be concerned, Cornelis said.
“Black might be better, but you’re not at increased risk because you’re adding sugar and milk,” she said.
Additives aside, moderation is key when it comes to coffee consumption, Zhang and O’Keefe emphasized, as any health benefits tend to wane after about two daily cups of coffee. Drinking more can even become dangerous.
“High doses of caffeine can be problematic with anxiety, irregular heartbeats, and elevated blood pressures,” said O’Keefe.
