The Star"buck"s Stops Here: What is the Role of Coffee/Caffeine on Long-Term Health?

            The market for coffee sales in the United States alone is $18 billion, owing to the fact that over 50% of Americans drink coffee daily, and the average coffee drinker consumes 3.1 cups of coffee per day.  Coffee consumption has sharply increased worldwide over the past several decades (Figure 1), although it has surprisingly decreased dramatically in the United States (Figure 2). 

Figure 1: Worldwide coffee consumption in weight by decade (www.unctad.info) .

Figure 2: Volume of coffee consumption in the United States by year www.marketwatch.com) .

            With so much recent focus on trendy nutritional regimens and the popularity of “chemical”-free diets such as gluten-free and organic, it is surprising that there has not been a greater public interest in the health effects of coffee.  Should we be drinking more, or drinking less? Fortunately, several studies have been performed assessing the association between coffee consumption and mortality.  While all of these studies exhibit the caveat of only evaluating correlations and not causal relationships, meaning that some other associated variable may actually be responsible for the observed effects (known as a cofactor), they can still provide useful information. 

Effects on Mortality
          A 2012 study performed by the National Institutes of Health found that when they controlled for both smoking status and age (since coffee drinkers were found to smoke more), a dose-dependent inverse relationship was observed between coffee consumption and mortality.  The results determined that coffee drinkers are less likely to die not only from a variety of health complications including stroke, heart disease, and respiratory disease (no beneficial result was observed for cancer), but also strangely from unnatural causes such as suicides/homicides and accidents.  While the effect of coffee drinking on unnatural deaths may seem somewhat random, however multiple reports suggest that caffeinated coffee consumption is associated with lower rates of depression and suicide. Similar beneficial effects of coffee consumption on reducing overall mortality were concluded in a more recent analysis examining data from multiple previous studies.  Additionally, while these studies failed to show any relationship between coffee/caffeine consumption and cancer risk, another meta-analysis (combining data from multiple studies) did show that a 3% reduction in cancer risk was observed for every additional cup of coffee consumed per day.

Health Risks from Caffeine
          Coffee has associated negative effects as well, mostly due to the caffeine content.  Coffee consumption should be limited for iron-deficient pregnant women and children, as it can contribute to anemia.  Immature liver development in newborns increases the length of time caffeine is present in the body, and rodent experiments suggest that high doses of caffeine can easily pass through the placenta to the fetal brain, resulting in sustained neurological effects. Based on these and similar studies, it is recommended that children and pregnant women restrict their caffeine intake. 

          
          While one would need to drink over 100 cups of coffee to ingest enough caffeine to kill them, caffeine intoxication can result from ingesting 300-400+ mg of caffeine at once (~2-4 cups of coffee).  Symptoms include anxiety, nausea, restlessness, and heart issues among others.  While these side effects should dissipate in normal adults within a few hours, long-term effects can result from caffeine addiction and subsequent withdrawal.  As I mentioned earlier, one study noticed as a side piece of information that smoking was more common among heavy coffee drinkers.  In fact, caffeine was found to promote nicotine addiction in rats, and caffeine can induce physical dependence similar to other addictive drugs.  Caffeine withdrawal is even now officially recognized as a psychiatric disease known as Caffeine Use Disorder in the Diagnostic and Statistical Manual of Mental Disorders (5th edition; DSM-5)!  Withdrawal symptoms are similar to that of caffeine intoxication and can amplify existing psychiatric and physical issues such as anxiety and fatigue, actually opposing its beneficial behavioral effects.

          Overall, coffee appears to have either a benign or even beneficial effect on long-term health when consumed in moderation.  However, sustained daily intake of even 1 cup of coffee per day can foster dependence, so caffeine should be viewed like any other drug.  Just like wine or beer, a low to moderate dose may have positive health affects, however the negative effects of abuse are potentially much stronger.  Just keep your weekly Starbucks budget to a minimum, and feel free to otherwise enjoy coffee as always.