The relationship between coffee and health has been steeped in scientific controversy for years. Scientists used to think that coffee was just a short-term boost in energy with long-term health consequences. But, recent research indicates that not only is coffee safe to drink, it can actually help you fight aging, possibly lower blood sugar and support a healthy liver.
In this blog post, we'll straighten out all the research for you and outline how you can use blood data to get the biggest boost from your daily cup of Joe.
This is partly because one cup of coffee contains about 80 mg - 170 mg of caffeine, a stimulant that improves attention span but may lead to some adverse health effects if consumed in excess. [5] In the 1970s and '80s, preliminary research on animals indicated that consuming coffee containing caffeine could lead to nasty health conditions such as cancer, heart disease, and birth defects. [6]
However, there's good news: the bulk of modern-day research suggests that coffee consumption is not only safe for most people who enjoy its taste, it may actually help your health in a variety of ways!
InnerAge is a feature and a blood panel available from InsideTracker. The chart above illustrates how choices and behaviors influence one's biological aging, versus one's chronological "Inner" age.
In 2008, the researchers followed up with the subjects and noted that about 13% had died. After adjusting for tobacco-smoking status and other variables, researchers observed a significant association between coffee consumption and reduced mortality. [7] This means that as someone drank more cups of coffee per day on average, they were less likely to die. [7]
Researchers also noted significant, inverse associations between coffee consumption and death due to infections, diabetes, heart disease, stroke, and injuries. [7] These inverse associations were also observed in people who had never smoked and individuals who reported “very good” or “excellent” health status at the beginning of the study. [7] However, they noted no inverse association between coffee consumption and risk of death from cancer.
Because of their promising data, the researchers stated that “coffee consumption was inversely associated with total and cause-specific mortality.” However, because they could not clearly adjust for all variables, they also emphasized that “whether this was a causal or associational finding cannot be determined from our data.” [7]
The findings of this study are supported by several others. Researchers from Harvard School of Medicine and Public Health noted a significant, inverse association between coffee consumption and mortality in three different studies with a total of 300,000 subjects.
The Harvard researchers concluded that “higher consumption of total coffee, caffeinated coffee, and decaffeinated coffee was associated with lower risk of total mortality.” [8] They also observed something else interesting: there was no significant difference between regular and decaf coffee and risk of death!
These research studies are promising. However, it's important to keep the findings in perspective. All of these studies were observational. This means that they cannot establish a clear causal relationship as to why coffee consumption led to lower death. Additionally, there are many other nutrition and lifestyle interventions that fight aging and may possibly extend life. Still, such studies do provide compelling evidence that your habit of drinking one or two (or four) cups of coffee per day might have a beneficial effect on the aging process. [9]
Key takeaways: Several observational studies show an inverse association between coffee consumption up to five cups per day and risk of death. However, a clear causal relationship between coffee and longevity cannot be established.
Recommendations: If you drink coffee or want to start drinking it, use InsideTracker’s InnerAge to see what impact it has on aging-related biomarkers such as C-reactive protein (CRP) and glucose. If you don’t want to drink coffee or can’t because it has a negative impact on your body, feel free to check out many of our other anti-aging interventions in our recommendation engine, included with each test.
The researchers discovered that as you drink more coffee, your risk of developing diabetes decreases. Drinking an additional cup of coffee per day led to a 7% reduction in the risk of developing type II diabetes. As a result of these findings, the researchers stated that “high intakes of coffee, decaffeinated coffee, and tea are associated with reduced risk of diabetes.” These findings are in line with several other studies. [10]
It is important to put the findings of this study in context:
Key takeaways: Data from observational studies indicates that drinking coffee regularly helps lower blood sugar and prevents the onset of diabetes.
Recommendations: If your blood sugar levels are elevated, consider adding a cup or two of black coffee a day and use InsideTracker to monitor your glucose.
In 2014, researchers assessed data on 27,793 subjects age 20 or older from a study called The U.S. National Health and Nutrition Examination Survey. The subjects had been monitored for 11 years. To measure the degree of toxicity, scientists collected data on three enzymes produced by the liver: alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transaminase (GGT) — all of which are measured in InsideTracker’s Ultimate Panel, by the way. Higher levels of these enzymes indicate greater levels of toxicity in the blood.
Researchers discovered that drinking at least three or more cups of coffee per day resulted in an inverse relationship with abnormal levels of liver enzymes. This means that coffee drinkers, overall, were less likely to have abnormal liver enzymes, most likely due to lower levels of “toxins”. These results were strongest for individuals who drank at least an average of three cups of coffee per day.
Another study on over 100,000 individuals illustrated strong inverse associations between coffee consumption and three liver enzymes, and cirrhosis of the liver, a condition in which the liver functions poorly due to long-term damage. 14 These observational studies on many subjects provide reasonable evidence that consuming coffee can help with detoxification.
Key takeaways: In observational studies, drinking three or more cups of coffee is associated with lower levels of the liver enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transaminase (GGT). Lower levels of these enzymes indicate a healthier liver.
Recommendation: If your levels of liver enzymes are high or you want to go on a detox cleanse, ditch the unproven juice cleanses and consider drinking up to three cups of coffee a day. Make sure it is unfiltered and monitor your liver enzymes (and personal health) to see how it affects you.
A recent meta-analysis of 12 research studies showed that, on average, drinking coffee for at least 6 weeks led to small but notable increases in triglycerides, total cholesterol, and LDL cholesterol. These increases were greater in subjects that already had high levels of lipids and in individuals who consumed more coffee. The researchers collectively summarized these findings by stating “the intake of coffee, especially unfiltered coffee, contributed significantly to the increase in LDL cholesterol and triglycerides, and the changes were related to the level of intake.” [15]
So, does this mean you should drop coffee altogether? Not necessarily. Some research indicates that coffee contains substances called dipterines that increase cholesterol. [16] Dipterines can easily be removed by using any filter, including of the paper variety.
Coffee is prepared by roasting and brewing coffee beans. Interestingly, these aren’t actual beans – they are seeds from the berries of the Coffea plant, which has its origins in subtropical Africa and South Asia. The two most commonly prepared coffee plants are the more refined Arabica and the earthy, strong robusta. [1]
The first documented use of coffee is in the Sufi Shrines of Yemen and in Medieval Ethiopia during the 15th century. [1] This makes it relatively "newer" than its main competitor, tea, which traces its origins back to thousands of years earlier. [2] By the end of the 16th century, coffee was widely consumed all throughout the Islamic world. In 1615, Italian merchants introduced coffee to Europe and it eventually caught on like wildfire in the Western world. [1] It was cheaper than tea, more caffeinated than chocolate, stimulated liveliness and humor but didn’t leave people with a hangover like wine. You can learn more about coffee’s interesting history by visiting the James Ford Bell Library website (University of Minnesota).
Even though tea had a few thousand years of a head start on coffee, they are now both the two most widely-consumed beverages, after water. About 2.25 billion cups of coffee are consumed worldwide per day. [3] According to the International Coffee Association, Finland has the highest coffee consumption per person; the average person there buys 22 pounds of coffee per year. The National Coffee Association pegs the United States is the overall biggest consumer of cup of Joe, however. About 54% of Americans ages 18 and older drink coffee at least once a day. The average American adults drinks 3.1 cups of coffee per day, which adds up to a total of 66 billion cups per year! [4]
List of References
1. "What is coffee?". National Coffee Association of USA. 2015. Retrieved 7 December 2015.
2. Heiss, Mary Lou, and Robert J. Heiss. The story of tea: a cultural history and drinking guide. Random House LLC, 2007.
3. Dicum, G., & Luttinger, N. (1999). The coffee book: anatomy of an industry from the crop to the last drop. New York: The New Press
4. National Coffee Association. "National coffee drinking trends 2009." New York (2010).
5. Castellanos, F. X., and J. L. Rapoport. "Effects of caffeine on development and behavior in infancy and childhood: a review of the published literature." Food and Chemical Toxicology 40.9 (2002): 1235-1242.
6. Troyer, Ronald J., and Gerald E. Markle. "Coffee drinking: an emerging social problem?." Social Problems (1984): 403-416.
7. Freedman, Neal D., et al. "Association of coffee drinking with total and cause-specific mortality." New England Journal of Medicine 366.20 (2012): 1891-1904.
8. Lopez-Garcia, Esther, et al. "The relationship of coffee consumption with mortality." Annals of internal medicine 148.12 (2008): 904-914.
9. Ding, Ming, et al. "Association of Coffee Consumption with Total and Cause-Specific Mortality in Three Large Prospective Cohorts." Circulation (2015): CIRCULATIONAHA-115.
10. Huxley, Rachel, et al. "Coffee, decaffeinated coffee, and tea consumption in relation to incident type 2 diabetes mellitus: a systematic review with meta-analysis." Archives of internal medicine 169.22 (2009): 2053-2063.
11. Xiao, Qian, et al. "Inverse associations of total and decaffeinated coffee with liver enzyme levels in National Health and Nutrition Examination Survey 1999‐2010." Hepatology 60.6 (2014): 2091-2098.
12. Casiglia, E., et al. "Unexpected effects of coffee consumption on liver enzymes." European journal of epidemiology 9.3 (1993): 293-297.
13. Ruhl, Constance E., and James E. Everhart. "Coffee and caffeine consumption reduce the risk of elevated serum alanine aminotransferase activity in the United States." Gastroenterology 128.1 (2005): 24-32.
14. Ruhl, Constance E., and James E. Everhart. "Coffee and tea consumption are associated with a lower incidence of chronic liver disease in the United States."Gastroenterology 129.6 (2005): 1928-1936.
15. Cai, L., et al. "The effect of coffee consumption on serum lipids: a meta-analysis of randomized controlled trials." European journal of clinical nutrition66.8 (2012): 872-877.
16. Bak, Annette AA, and Diederick E. Grobbee. "The effect on serum cholesterol levels of coffee brewed by filtering or boiling." New England Journal of Medicine321.21 (1989): 1432-1437.