In this article by the New York Presbyterian Health Matters, the claim is that “A study of nearly 500,000 British adults over a 10-year period showed that those who drank coffee were likely to live longer than non-coffee drinkers.” They included everything involving medical histories as well to get a full-rounded picture. Research shows that coffee contains antioxidants and anti-inflammatory properties that could be useful in reducing cancer risks and general aging. They also claim that people who drink 7-8 cups of coffee a day are more likely to live longer than people who only drink a couple of cups a day. So the more coffee, the better.
In another article by Healthline, they claim that out of 402,260 people aged 50–71 “The sweet spot appeared to be a coffee intake of 4–5 cups per day. At this quantity, men and women had a 12% and 16 % reduced risk of early death, respectively. Drinking 6 or more cups per day provided no additional benefit.” There is no factual research proving that the more coffee you drink, the longer you will live. Even drinking just one cup a day causes a 5-6% decreased risk of dying early.
https://www.healthline.com/nutrition/how-coffee-makes-you-live-longer#longevity
What is it about coffee that decreases the risk of death?
A quote from PubMed Central: “Coffee is rich in polyphenols, a group of compounds with antioxidant and anti-inflammatory activity which can be divided according to their chemical structure into flavonoids and non-flavonoids [15,16]. Some meta-analyses have shown that flavonoids and some non-flavonoids such as lignans with weak estrogen-like activity may have beneficial effects against cardiovascular disease and some cancers [15], although more evidence on specific compounds is still needed.”
https://pmc.ncbi.nlm.nih.gov/articles/PMC8070495/#:~:text=The%20mechanisms%20by%20which%20coffee,components%20%5B10%2C11%5D.
There is a close association with a decreased risk of diabetes. The polyphenols found in coffee are rich in antioxidants which neutralize the free radicals, which are defined as “highly reactive and unstable molecules that are made by the body naturally as a byproduct of normal metabolism” (https://www.verywellhealth.com/information-about-free-radicals-2249103#:~:text=Free%20radicals%20are%20highly%20reactive,and%20ultraviolet%20(UV)%20light.)
These antioxidants reduce the risk of heart disease, and the minerals chromium and magnesium (also found in coffee) are found to increase insulin sensitivity and promote turning glucose into energy. These studies are found in the long-term effects of drinking coffee, not temporarily. “Higher coffee consumption was associated with lower levels of CRP and leptin, pro-inflammatory markers, and higher levels of interleukin-13 and adiponectin concentrations, which have anti-inflammatory effects.” (https://www.healthline.com/health-news/a-daily-coffee-may-reduce-your-type-2-diabetes-risk#Enjoy-your-coffee-but-don-t-rely-on-it) It is important to make sure to drink filtered or espresso coffee for the best effects.