Humans have enjoyed tea
and coffee for quite some time. Coffee was being drunk in Europe in the mid-17th
century, while tea was supposedly consumed by the Chinese 4500 years ago,
although this strongly disputed as the first mention of tea in a Chinese text
was only 2000 years ago. Tea arrived in Europe around the same time as coffee.
A fascinating history of both beverages can be found in Tom Standage’s [http://tomstandage.wordpress.com/books/a-history-of-the-world-in-six-glasses/
A history of the world in 6 glasses].
The news is good
Long time readers will
remember I have said good things about tea and coffee before, because I prefer
a positive food story rather than the scare stories enjoyed by others. It is
always comforting to have science on your side. A meta-analysis (Mostofsky
2012) crunched all the research papers between 1966-2011, which included 140,000
coffee drinkers. They concluded: “Moderate coffee consumption is inversely
associated with the risk of heart failure, with the largest inverse association
observed for consumption of 4 servings per day.” And it didn’t matter whether
you’re a boy or a girl.
With four cups of coffee
a day there was a 11% lower risk of heart failure. Any benefit was negated once
you reached 10 cups a day. The analysis took account of body weight, alcohol
consumption and smoking, as is always the way in making sense of research.
And then it gets better
Some scientists who live
just down the road from me at the University of Western Australia took a look
at both tea and coffee and the potential risk of heart disease (Bøhn 2012). They also were positive about a lower risk of heart disease in tea
and coffee consumers after reviewing the published evidence.
Tea seemed to improve the
normal functioning of the arterial walls, lower triglycerides, inhibit
inflammation and LDL-cholesterol oxidation (the latter two significantly contribute
to atherosclerosis) and even lower the risk of stroke. Both tea and coffee are
associated with a lower risk of type 2 diabetes. The association seems to be
strongest with coffee, possibly due to the chlorogenic acids in coffee.
How much tea and coffee?
Difficult to say
precisely, but there is general agreement that 3-5 cups a day is having a
useful effect on your health. They did emphasise that genetics could be playing
an important role, meaning we can’t say that everyone will benefit from tea and
coffee. For example, those with the polymorphism CYP1A2 in the P450 enzyme (that’s
laboratory clever people talk I think) are slow caffeine metabolisers, and
actually have a higher risk of a heart attack with caffeinated drinks.
All the same, it sounds very
encouraging to me.
Is there a “yes, but...?"
Isn’t there always?
Generally, the studies rely on self-reported tea and coffee consumption and
only one point in time. If you believe that tea and coffee are “bad” then you
will probably fib about how much you guzzle, and often people just plain “forget”
how much they drink and therefore under-report. Or they may have changed
drinking habits over time depending upon what they read in the paper.
Association is not
necessarily cause and effect. It could also be that the folk enjoying a brew three
or four or five times a day might also eat more vegetables, watch only documentaries,
cook proper meals, help their neighbours, give to charity, walk the dog and hug
the kids.
Nevertheless, when the
numbers are given a thorough massage, it looks like moderate tea and coffee
drinkers come out ahead in the health stakes,
What does it all mean?
If you drink tea or
coffee, feel very comfortable with the habit. All the evidence suggests that up
to five cups a day is fine and may even be a generous leg-up for your health. I
suspect that even 6-8 cups a day is OK. Twenty cups? I’m not so sure. Worth considering
a cut back. No-one is certain what specific compounds in tea and coffee are
responsible for their proposed protection. There are many biologically active
compounds, both known and unknown, in tea and coffee.
Between you and I, six
cups of tea a day find their way down my throat. They are big cups and I ain’t
worried in the slightest. Hopefully, before I die, science will reveal why tea
helped me live to 105.
References:
Mostofsky E
et al. Circulation Heart Failure 2012; DOI:
10.1161/circheartfailure.112.9672299
Bøhn SK et al. Food
& Function 2012 DOI:10.1039/c2fo10288a
