CAFFEINE CONTENTS
COFFEE
The amount of caffeine in a cup of coffee can
vary greatly, depending on its origin or the composition of the blend, the
method of brewing and the strength of the brew. Instant, or soluble, coffee
generally contains less caffeine than roast and ground coffee, but may be
consumed in greater volume. Robusta coffees have about twice as much caffeine
as Arabicas. A 'cup' is usually understood to contain 150 ml (5 oz in the
United States) but an espresso may be as small as 40 ml.
The U.S. Food and Drug Administration gives the
following ranges for caffeine contents:
(mg per 5 oz cup)
|
|
range |
average |
|
Roast and ground |
|
|
|
Instant coffee |
30-120 |
65 |
Consumer surveys
An interesting survey of caffeine contents in
cups of coffee was conducted in Canada. Whether the coffee was prepared by
housewives at home, for sale in commercial outlets, or by individuals at work,
the mean caffeine content was about 80 mg per cup (about 350 mcg per ml). The
means for roast and ground coffee, both drip and percolator brewed, were below
85 mg; for instant coffee 71 mg. However, the range of measurements was so wide
that, for most individuals, it would be inaccurate to use these figures as a
basis for calculating the exact amount of caffeine consumed in a day. The size
of the cup/serving varied from 25 ml (Greek coffee) to 330 ml at home and from
130 ml to 280 ml in the out-of-home situation.
DECAFFEINATED COFFEE
Whatever method of decaffeination is used, the
decaffeinated green coffee must contain less than 0.1 % caffeine (dry weight
basis) to comply with EC regulations. This corresponds to about 3mg caffeine in
a cup of decaffeinated coffee.
OTHER BEVERAGES
Tea contains more caffeine
than coffee weight for weight, but less weight is used, in general, to brew a
cup of tea. In the Canadian study referred to above, both the type of tea used
and the steeping time affected the caffeine concentration of samples prepared
in the laboratory as follows:
(mean, mcg per ml)
|
|
2 minutes |
5 minutes |
|
Tea-bag |
238 |
402 |
|
Loose tea |
189 |
295 |
The average caffeine concentration of samples
of tea prepared at home was lower, at 159 mcg per ml, but with a wide
variation.
The caffeine content of a cup of tea is usually
less than 60 mg, but a strong cup of tea may contain more caffeine than a weak
cup of regular coffee.
Cocoa and chocolate drinks contribute 4-Smg caffeine per cup to the diet, dark chocolate
and cooking chocolate 20-26mg per ounce (0.7-0.9mg per gram). Many soft
drinks, including colas and "peppers", contain caffeine, which as
well as being present in cola nuts is often added as a flavour ingredient. A
12-ounce serving may contain 30-60mg caffeine. The major brands of cola on sale
in the UK contain about 120mg caffeine per litre.
DRUGS
Caffeine is present in many prescription and
non-prescription (over-the-counter) drugs, including some taken for headache,
pain relief, appetite control, staying awake, colds, asthma and fluid
retention. The caffeine contents of drugs varies from 7mg to 200mg per tablet.
LEVELS OF CAFFEINE CONSUMPTION
Caffeine is generally consumed in amounts less
than 300mg per day, roughly equivalent to:
3-4 cups of roast and ground coffee
5 cups of instant coffee
5 cups of tea
6 servings of some colas or
10 tablets of some painkillers
It has been suggested that the British consume
more caffeine on average than Americans, but there are no large scale studies
to support the observation. The nine, normal subjects recruited by Dr M.S.
Bruce and his colleagues, as habitual caffeine users, for a study in London
(reference below) were found to consume on average 428mg caffeine a day, with a
range from 230mg to 670mg.
Customary caffeine consumption has been
classified as follows:
Low caffeine users: less than 200mg per day
Moderate caffeine users: 200-400mg per day
High caffeine users: more than 400mg per day
