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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.”[1]
Third, independent researchers suggest that consuming
caffeinated coffee may be linked to improved brain function, physical
endurance, and athletic performance.[2]
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.[3] 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.
Footnotes
[1] 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.
[2] 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.
[3] 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.
Source: https://nationalcoffeeblog.org
Association of Coffee Consumption with Total and Cause-Specific
Mortality in Three Large Prospective Cohorts, An Abstract
Source:
http://circ.ahajournals.org/
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.
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