New England Journal of Medicine July 23, 2020 “Coffee, Caffeine, and Health” by RM van Dam, FB Hu, and WC Willett.
Certainly a topic that captures the interest of many. As it turns out, coffee and caffeine in America are tightly-linked making it difficult to tease-out the direct of effects of Caffeine versus many other substances in coffee. The direct effects of caffeine as a standalone are more clearly deciphered.
“A large body of evidence suggests that consumption of caffeinated coffee…does not increase the risk of cardiovascular diseases and cancers.” Moderate consumption of coffee defined as 3-5 standard cups per day has been “consistently associated with a reduced risk of several chronic diseases." Higher caffeine can have “various adverse effects” this review suggests limiting intake to 400 mg/day for adults and 200 mg/day for pregnant and lactating women. Moderate consumption of coffee or tea can be part of a healthy lifestyle but “current evidence does not warrant recommending caffeine or coffee intake for disease prevention.”
Besides caffeine coffee contains hundreds of other biologically active phytochemicals and “modest amounts of magnesium, potassium and vitamin b1 (niacin).” It is believed that “these coffee compounds may reduce oxidative stress, improve the gut microbiome and modulate glucose and fat metabolism.” One substance, in unfiltered coffee, diterpene cafestol raises cholesterol levels.
Caffeine structurally resembles adenosine and this mimicry inhibits activation of adenosine pathways. “Accumulation of adenosine in the brain inhibits arousal and increases drowsiness.” This caffeine action is helpful to “improve vigilance during tasks of longer duration that provide limited stimulation, such as working on an assembly line, long-distance driving and flying aircraft.” Because caffeine is metabolized in the liver by cytochrome P450 other compounds including drugs using the same method can increase the half-life of caffeine beyond the usual of 2.5-4.5 hours. Of concern, is that pregnancy greatly reduces caffeine metabolism and can increase the half-life to as many as 15 hours.
Caffeine “can contribute to pain relief when added to commonly used analgesic agents.” Having said that, caffeine can be toxic at very high levels typically encountered when taking tablets or supplements. Energy drinks and shots, “especially when mixed with alcohol, has also been linked to adverse cardiovascular, psychological, and neurologic events, including fatal events.”
“An inverse association has been observed between coffee consumption and coronary artery disease, stroke and death from cardiovascular causes.”
“Habitual coffee consumption has been consistently associated with a reduce risk of type 2 diabetes” regardless of caffeine content.
“The results of many prospective cohort studies provide strong evidence that consumption of coffee and caffeine is not associated with an increased incidence of cancer.”
“In U.S. cohorts, …coffee was associated with a reduced risk of kidney stones” and gallstones with only a lower risk of gallbladder cancer being more strongly associated with higher caffeine content in coffee.
“A strong inverse association between caffeine intake and the risk of Parkinson’s disease”. “Coffee consumption has not been consistently associated with the risk of dementia or Alzheimer’s disease.” “Coffee and caffeine consumption have also been associated with reduced risk of depression and suicide.”
“Consumption of 2 to 5 standard cups of coffee per day has been associated with reduced mortality in cohort studies across the world.”
“In prospective studies, higher caffeine intake has been associated with lower birth weight and a higher risk of pregnancy loss.” Suggested to have no more than 200 mg/day when preganant or lactating.