GUEST BLOG / By Bill M. Murray, National Coffee Association--We know that coffee helps fight fatigue – but how do we know this?
First, from personal observation – coffee drinkers feel the effects of caffeine, and sometimes observe them in others.
Second, there’s evidence in the form of coffee-drinker surveys. In 2016, 84% of coffee drinkers said that “coffee wakes me up and gets me going.”
Third, independent researchers suggest that consuming caffeinated coffee may be linked to improved brain function, physical endurance, and athletic performance.
Three different types of research, all leading to similar conclusions.
But when it comes to diet and health-related research, there are new headlines every day – sometimes with opposite claims. Coffee itself isn’t immune from this phenomenon, and it’s easy to see why.
Since the early 1990’s, at least 2,700 coffee and health related studies have been reported by researchers from all around the world. With new coffee and health headlines emerging on a weekly basis, it is important that coffee drinkers think smart about the coffee and health news that breaks over their morning cup of coffee, some of which may even appear to be contradictory.
If you’re trying to stay up-to-date on coffee and health research, here are 4 things to keep in mind when reading the headlines.
1. What is the “bottom line” when it comes to coffee?
Or to pose the question differently, “what is the overall impact on my life?”
In the case of coffee, a Harvard affiliated study found that “Higher consumption of total coffee…was associated with lower risks of mortality,” echoing a study from the National Institutes of Health which concluded that “coffee drinkers have a lower risk of death.”
That’s a pretty solid bottom line.
2. What does most of the research on a particular topic conclude?
The “preponderance of evidence” assessment is one way to do this. If 200 studies have been done on liver cancer, what do most of them say? Another approach used by scientists is meta-analysis – a way of combining and assessing the results from multiple studies.
For example, in the case of liver cancer and coffee drinkers, meta-analysis suggests that increased consumption of coffee may reduce the incidence of liver cancer. This conclusion, then, isn’t just based upon one study that may be in the headlines.
3. Who has cited, published, or reported deeply on the research?
There are well-respected organizations that apply professional expertise to health and nutrition questions as a public service: Mayo Clinic, Harvard School of Public Health. They choose references, and with whom they associate, very carefully, and some news organizations go beyond the headline to ask thoughtful questions about a research topic.
4. Were there methodological defects that could call the research findings into doubt?
Coffee traders know that defects in their shipment can affect taste, price, and their reputation. When it comes to coffee related health research, there are technical defects to be avoided. These are sometimes mentioned in coverage of health-related research, and can include:
Study design. The case-control approach to research – which typically involves patients who’ve already developed a disease – is less expensive than alternates, but subject to many potential defects. For example, chosing the “control” group – the population without a disease – must be done carefully to ensure that it is an appropriate sample. And, the case-control design can face additional challenges, as can some others, such as “recall bias.”
Recall bias. Subjects’ having poor memory of specific behaviors. (Can you remember how much coffee you drank five years ago?)
Failing to account for other factors that can affect health outcomes. For example, pregnant women will often not admit to researchers if they have consumed alcohol, or if they smoked cigarettes which can lead to incorrect research conclusions.
The pregnancy signal. Women who have more viable pregnancies naturally develop a hormone-induced aversion to strong smells, which can lead them to drink less coffee. Those who do not experience this “pregnancy signal” are likely to have less viable pregnancies – and as a result, will tend to continue with their normal coffee consumption. This can lead to misinterpretation of study outcomes. (Read more about the fascinating, complex issue of the “pregnancy signal.”)
We live today in the “information age,” which can be a mixed blessing when we’re overwhelmed with conflicting headlines. Until new techniques are developed to automatically separate the well done studies from the not-so-good, we’ll use these guidelines to help sort through the headlines (and beyond) to determine what research to highlight on the NCA Coffee & Me website.
And hopefully these pointers will help you, the informed coffee drinker. When the next coffee-related health story sails across the internet, you can make the right decision – for yourself – about what role, if any, that coffee should play in your own life.
 From the NCA’s National Coffee Drinking Trends Study 2016, based upon a representative sample of 2,782 people over the age of 18 across the U.S.
 See, for example:
Memory: Smith AP. Caffeine, extraversion and working memory. J Psychopharmacol. 2013 Jan;27(1):71-6.
Sleep deprivation and stress: Lieberman HR, Tharion WJ, Shukitt-Hale B, Speckman KL, Tulley R. Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training. Sea-Air-Land. Psychopharmacology (Berl) 2002; 164(3):250-61.
Work performance: Smith AP. Caffeine at work. Hum Psychopharmacol. 2005 Aug;20(6):441-5.
Performance and sleep apnea: Norman D, Bardwell WA, Loredo JS, Ancoli-Israel S, Heaton RK, Dimsdale JE. Caffeine intake is independently associated with neuropsychological performance in patients with obstructive sleep apnea. Sleep Breath 2008;12(3):199-205.
Cognitive function of non-working individuals: Smith AP. Caffeine, cognitive failures and health in a non-working community sample. Hum Psychopharmacol. 2009 Jan;24(1):29-34.
 The NCA itself does not typically fund published research regarding the health effects of consuming coffee, has not done so for over a decade, and has no plans at present to provide such funding to any entity.
Association of Coffee Consumption with Total and Cause-Specific Mortality in Three Large Prospective Cohorts, An Abstract
Background—The association between consumption of caffeinated and decaffeinated coffee and risk of mortality remains inconclusive.
Methods and Results—We examined the associations of consumption of total, caffeinated, and decaffeinated coffee with risk of subsequent total and cause-specific mortality among 74,890 women in the Nurses' Health Study (NHS), 93,054 women in the NHS 2, and 40,557 men in the Health Professionals Follow-up Study. Coffee consumption was assessed at baseline using a semi-quantitative food frequency questionnaire. During 4,690,072 person-years of follow-up, 19,524 women and 12,432 men died. Consumption of total, caffeinated, and decaffeinated coffee were non-linearly associated with mortality. Compared to non-drinkers, coffee consumption one to five cups/d was associated with lower risk of mortality, while coffee consumption more than five cups/d was not associated with risk of mortality. However, when restricting to never smokers, compared to non-drinkers, the HRs of mortality were 0.94 (0.89 to 0.99) for ≤ 1 cup/d, 0.92 (0.87 to 0.97) for 1.1-3 cups/d, 0.85 (0.79 to 0.92) for 3.1-5 cups/d, and 0.88 (0.78 to 0.99) for > 5 cups/d (p for non-linearity = 0.32; p for trend < 0.001). Significant inverse associations were observed for caffeinated (p for trend < 0.001) and decaffeinated coffee (p for trend = 0.022). Significant inverse associations were observed between coffee consumption and deaths due to cardiovascular disease, neurological diseases, and suicide. No significant association between coffee consumption and total cancer mortality was found.
Conclusions—Higher consumption of total coffee, caffeinated coffee, and decaffeinated coffee was associated with lower risk of total mortality.
Authors of the Study:
--Ming Ding, Ambika Satija, Shilpa N. Bhupathiraju and Yang Hu, Harvard School of Public Health, Boston’
--Frank B. Hu, Walter Willett and Qi Sun, Harvard School of Public Health & Brigham and Women’s Hospital and Harvard Medical School, Boston
--Jiali Han, Indiana University, Indianapolis
--Esther Lopez-Garcia, Universidad Autonoma de Madrid/idiPaz, Ciber of Epidemiology and Public Health, Madrid
--Rob M. van Dam, Harvard School of Public Heath, Boston and National University of Singapore and National University Health System, Singapore.