How many cups of coffee can you drink daily before it becomes unhealthy?
How much caffeine is too much?
Latest research has shed more light on the effect of caffeine on cardiovascular health. According to the American Heart Association's most recent study, five cups of caffeinated coffee should be the daily limit for most adults.
"In our review of the most recent research, for most adults, intake of up to 400 mg of caffeine/day, the equivalent of up to five cups of caffeinated coffee per day without added sugars or fillers, is safe and does not increase cardiovascular risk," said Gregory M. Marcus, MD, MAS, FAHA, professor of medicine at the University of California, San Francisco School of Medicine and chair of the scientific statement volunteer writing group.
Marcus referred to findings published in the scientific statement, "Caffeine and Cardiovascular Disease," published Monday in AHA's flagship peer-reviewed scientific journal Circulation.
Effects of caffeinated coffee on health
The study focuses on black caffeinated coffee taken without sugars, sweeteners, flavors, or added fillers. One fluid ounce of this regular-brewed, non-specialty coffee usually contains 9.4–20.6 mg of caffeine.
Generally, for adults, drinking up to five eight-ounce cups of this kind of coffee can produce significant effects on the body.
Type 2 diabetes
Research has found caffeinated coffee to help reduce short-term insulin sensitivity. Black coffee has also been found to reduce the risk of developing Type 2 diabetes. However, more research is needed to determine if this effect is brought about by the caffeine in black coffee or other compounds.
Blood pressure
People with optimal blood pressure who drink one to three cups of coffee daily have been found to have an increased risk of developing high blood pressure. Those who go over three cups per day were determined to have a lower risk.
The risk significantly increases in people who regularly consume high doses of caffeine, which usually come from energy drinks or energy shots.
Cholesterol
Both caffeinated and decaffeinated coffee contain cafestol, a component associated with higher levels of low-density lipoprotein, or "bad" cholesterol. Researchers have found cafestol in unfiltered coffee, including espresso, French press, Turkish coffee, and boiled coffee. The compound hasn't been detected in instant coffee and coffee brewed using paper filters.
Heart rhythm
Studies have found that drinking one to three cups of caffeinated coffee every day is not linked to an increased risk of atrial fibrillation, or an abnormal heart rhythm. The same amount of caffeine has also been seen to bring about more early beats from the heart's lower chamber, i.e., premature ventricular contractions. These feel like fluttering in the chest, or skipped beats.
According to the Mayo Clinic, PVC in people with healthy hearts is not usually concerning. High doses of caffeine, however, are associated with abnormal heart rhythm even in healthy adults under 30.
Heart disease and stroke
Two to four cups of caffeinated coffee per day have been found to lower risk of heart disease, heart failure, and stroke. Over four cups daily may raise the risk of heart failure.
No 'one-size-fits-all strategy'
The most recent study published by AHA focused on caffeine contained in coffee as more conclusive research is yet to be done on other caffeinated sources, including energy drinks, tea, chocolate, soda, and over-the-counter and prescription medicines.
These usually contain added ingredients that increase the body's capacity to absorb caffeine, which speeds up its effects, raising blood pressure and the risk of cardiovascular danger.
Some research has been done on the effects of tea. Partial findings have said tea is linked to reduced risk of atrial fibrillation, heart failure, and stroke.
Marcus explains the results of the latest study don't apply to everyone.
"Although research suggests that caffeine consumption may be associated with certain cardiovascular benefits for some people, it's important to remember that there is no 'one-size-fits-all strategy for safe caffeine consumption," he wrote.
Various factors, such as age, medications, underlying health conditions, genetics, and metabolism rate can affect how the body reacts to daily caffeine intake. What is a healthy amount for one may be dangerous for another.
"That's why it's important to pay attention to how your body responds to caffeine and talke with your healthcare team about what is right for you," Marcus said.