Are you one of those doctors who powers through the day on endless cups of coffee—and then wonders whether it’s good for you? Like meat, eggs, fat, and carbs, scientists have long flip-flopped on the ups and downs of coffee consumption and its effects on health. Does it help protect from cardiovascular disease? Will a cup of joe lead to poorer sleep quality and increased anxiety? Should you stop drinking coffee if you’re pregnant? Can it add years to your life?
Here’s a selection of the latest research on coffee and what it does to our bodies.
Researchers are still investigating the link between coffee consumption and longevity, but recent findings are promising. A new study published in the Journal of Nutrition measured associations between coffee consumption and total- and cause-specific mortality. Using data from more than 20,000 healthy Italian men and women, researchers tracked dietary patterns and various health biomarkers over roughly 8 years.
The researchers found that moderate coffee consumption (3–4 cups per day) was associated with decreased risks of cardiovascular-specific and all-cause mortality.
These findings are corroborated by a recent meta-analysis published in Advances in Nutrition. The researchers found that coffee consumption was associated with a range of desirable health outcomes. The authors examined 26 studies that included 3.7 million participants, focusing on dose-response associations between coffee consumption and incidence/mortality of cardiovascular disease, type 2 diabetes, and several types of cancer.
They found that, in any coffee-drinkers, there was a significant inverse association with the risk of cardiovascular disease (RR = 0.90; 95% CI: 0.84, 0.96), type 2 diabetes (RR = 0.90; 95% CI: 0.85, 0.96), endometrial cancer (RR = 0.85; 95% CI: 0.78, 0.92), melanoma (RR = 0.89; 95% CI: 0.80, 0.99), and nonmelanoma skin cancer (RR = 0.92; 95% CI: 0.89, 0.95).
Results showed that drinking 3–4 cups of coffee per day provided the best risk reduction for cardiovascular disease, while the risk decreased in a linear fashion over the whole coffee consumption range for other outcomes.
Coffee consumption accounts for 6%–12% of avoided deaths among the health outcomes explored, the authors wrote, adding that the analysis confirmed that coffee consumption had beneficial health impacts.
Likewise, a review article published in the New England Journal of Medicine (NEJM) found that the consumption of 2–5 standard cups of coffee per day was associated with reduced mortality in studies conducted throughout the world and across various demographics. They even concluded that consumption of more than 5 cups per day was associated with lower or similar risks of all-cause mortality than no consumption.
Blood pressure and cardiovascular disease
Other recent studies have focused on the relationship between coffee and heart health. An analysis published in Circulation: Heart Failure looked at data from three large studies that included more than 13,000 participants.
Researchers monitored dietary and behavioral risk factors for cardiovascular disease outcomes including marital status and consumption of red meat, whole milk, and coffee. In all three studies, the findings indicated that increased coffee consumption was associated with a decreased long-term risk of heart failure. In one of the studies, elderly individuals who consumed any caffeinated coffee had a 43% reduction in cardiovascular-related deaths compared with those who never consumed coffee.
The analysis represents just a sliver of the recent research that has arrived at a similar conclusion. The authors of the aforementioned NEJM review found that a sudden intake of caffeine raised epinephrine levels and blood pressure in the short term in those who hadn’t previously consumed coffee.
However, studies involving habitual coffee drinkers have generally reported no substantial impact on blood pressure, even in those with hypertension. The authors hypothesized that this is due to the various other compounds in coffee, like chlorogenic acid, which may counter the hypertensive effects of the caffeine.
Additionally, the authors noted that studies have consistently found that the consumption of up to 6 cups of coffee per day is not associated with an increased risk of cardiovascular outcomes in the general population or in those with hypertension, diabetes, or cardiovascular diseases, when compared with no coffee consumption.
Coffee contains hundreds of biologically active phytochemicals, including polyphenols, the alkaloid trigonelline, and modest amounts of magnesium, potassium, and vitamin B3. These compounds may play a role in reducing oxidative stress, improving the gut microbiome, and mediating glucose and fat metabolism, but further research is required to confirm this.
While it’s becoming increasingly clear that some coffee consumption is beneficial for health, the beverage’s benefits in pregnant women remain controversial. A majority of pregnant women drink caffeinated beverages daily, and current health advice states that moderate consumption during pregnancy is safe. However, according to a review published in BMJ, this advice should be reconsidered.
The review included 48 studies and analyses published over the past two decades, and focused on the relationship between coffee consumption and negative pregnancy outcomes. A majority of the studies in the review provided evidence that coffee consumption during pregnancy increased the risks of all negative pregnancy outcomes except for preterm birth. Likewise, a majority of the analyses concluded that maternal caffeine consumption was associated with increased risk for miscarriage, stillbirth, low birth weight, and childhood acute leukemia. The researchers concluded that cumulative evidence suggests that pregnant women and women who are planning to become pregnant should avoid caffeine completely.
The aforementioned NEJM review reports similar findings. Its authors found evidence that caffeine passing through the placenta can induce uteroplacental vasoconstriction and hypoxia by increasing blood catecholamine levels in both the mother and fetus. The authors concluded that coffee consumption during pregnancy should be limited to a maximum of 200 mg per day.
When it comes to coffee consumption and risk of cancer, the evidence indicates coffee has different benefits in different cancer types.
For example, authors of a recent review published in BMJ examined the impact of coffee consumption on prostate cancer risk. After looking at 16 studies that included data on more than 1 million participants, the researchers found that increased coffee consumption was significantly associated with a lower risk of prostate cancer. The findings showed that, for those in the highest category of coffee consumption, the pooled relative risk was 0.91 (95% CI 0.84 to 0.98, I2= 53.2%), when compared with the lowest levels of coffee consumption.
On the other hand, a study published in the International Journal of Cancer showed that coffee may not have the same effect on lung cancer. The study included 17 cohorts with more than 1.1 million participants who were monitored for 8 years. During that time, 20,280 incident lung cancer cases were diagnosed. Compared with no caffeine consumption, hazard ratios associated with coffee drinkers among current, former, and never smokers were 1.30 (1.15–1.47), 1.49 (1.27–1.74) and 1.35 (1.15–1.58), respectively. The researchers concluded that a higher level of caffeine consumption was associated with increased risk of lung cancer, although they noted that the findings may be confounded by participants’ smoking habits.
An individualistic approach
While the studies and reviews cited above generally point toward coffee as fairly healthful (or at least something with relatively few adverse health impacts), the authors of the NEJM review point out that everyone reacts to caffeine differently.
While a large body of evidence suggests that 3–5 cups of coffee a day is associated with a reduced risk of several chronic diseases, high caffeine intake can still have negative impacts on certain individuals due to variations in personal metabolism and sensitivity to caffeine.
While the current evidence doesn’t indicate that coffee can be treated as a preventative measure against diseases, it does suggest that a few cups a day can be part of a healthy diet.