Coffee represents one of the largest markets in the world. While many enjoy coffee, some press reports have suggested health concerns. However, the thousands of studies on coffee and caffeine have had inconsistent and contradictory results. Caffeine is found in many foods and drinks, including coffee, tea, chocolate, and medications. As a stimulant, caffeine provides mental and physical benefits, but larger epidemiological studies have not found clear links between coffee drinking and fertility or pregnancy issues despite some initial suggestions of delayed conception from smaller studies.

1. NUTRITION &
FOOD SCIENCE
Coffee, Caffeine and Health:
The Real Story
Sophia Papadopoulos
In recent times, the re-emergence of even bias, and so requires careful evaluation.
fashionable coffee bars with shining coffee Study sizes, protocols, methodologies, and
machines serving espresso and cappuccino, levels of control for confounding factors
and the growing interest and availability of (such as smoking or alcohol consumption)
higher grade instant, and roast and ground can all play a part in influencing the
coffees, has created a revitalized market for direction of results.
coffee in the UK. Coffee actually represents
one of the largest markets in the world —
second only to oil — and some 20 million
people rely on this for employment. Caffeine's Actions
However, though nearly all of us enjoy a The alkaloid, caffeine (1,3,7-trimethylxanthine), is
cup of coffee, the odd article in the press has one of a group of naturally occurring
firmly planted a niggling feeling that our compounds found throughout the plant kingdom.
Although most commonly associated with coffee,
coffee (or perhaps it is the caffeine?), isn't a range of everyday foods, drinks and other
really doing us any good. In fact, these few products contain caffeine to varying degrees (see
publicized reports do not tell the whole story. Table I). Tea (which actually contains more
caffeine than coffee on a dry weight basis), colas,
chocolate, and some over-the-counter and
prescription medications also contain caffeine.
COFFEE UNDER SCRUTINY Caffeine is a mild central nervous system
The ubiquitous use of coffee (and caffeine) stimulant, and its actions as an adenosine
worldwide has led to. exhaustive investigations antagonist are thought to be largely responsible
into their potential health effects, and for the well-documented and beneficial pick-me-
up and concentration-enhancing properties of a
medical texts date right back to the 1850s. cup or two of coffee[l]. Other minor effects at
Over the last few decades perhaps thousands the cellular level have also been postulated,
of papers have been published, yet only a including caffeine's actions as a
tiny amount of this research ever reaches the phosphodiesterase inhibitor — acting to increase
public eye, and thus it is not surprising that cellular levels of cyclic AMP (one of the cells'
messenger molecules) — caffeine-related plasma
misconceptions and unnecessary concerns are elevation of certain catecholamines (such as
common. epinephrine), and its effects (in vitro) on
However, the fact that so much data on intracellular calcium translocation and skeletal
coffee and caffeine exists does not always muscle contractiIity[2,3]. However, whether these
make interpretation any easier, even when it have any real physiological effects has not been
defined, and is debated.
is all to hand. Interventional trials and Caffeine has also been found to increase the
epidemiological (population) studies form the efficacy of common pain-killing analgesics such
backbone of coffee/caffeine and health as paracetamol and aspirin[4,5], and to exhibit a
research, and it is all too apparent that certain amount of analgesic action
epidemiological research especially can be independently[6].
fraught with pitfalls, inconsistencies, and In addition, the bronchodilatory actions of
caffeine and its relative, theophylline, are used in
the treatment of neonatal apnoea (severe
Nutrition & Food Science, No. 1, January/February 1993, pp. 28-33 breathing difficulties) in premature babies[7,8].
© MCB University Press, 0034-6659.
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2. NUMBER 1
JANUARY/FEBRUARY 1993
drinking coffee is associated with delayed
Type of coffee/ Size of cup Approximatea
beverage caffeine
time to conception, or subfecundity[10].
content (mg) These conclusions were, in fact, drawn
from a study of just 104 women, which was
Instant (heaped tsp) any size 50-60 not designed to investigate specific caffeine
Drip filtered medium (125 ml) 60-100 effects on fertility. The women questioned
Percolated medium (125 ml) 60-100 had all failed to get pregnant within the first
Espresso small (80 ml) 70-80 three months, and the study did not consider
Decaffeinated medium-large 2-4
those who did achieve pregnancy within three
(125-200 ml) months. The authors actually note "a lack of
Tea medium (125 ml) 30-60b association between caffeine consumption
Cola (regular or
and fecundability in the first two cycles".
diet) 330 ml can 40-45 In contrast, a subsequent, far larger and
a
The amount of caffeine in any cup of caffeinated more thorough investigation on 2,817 women
beverage can vary quite considerably, and, for actually found no association whatsoever
coffee, is dependent on the amount used to make between caffeinated beverage consumption
the brew, and the size of the cup. and either delayed conception or
b
Although tea contains more caffeine than coffee on infertility[ll].
a dry weight basis, less weight of tea is generally
used to brew a cup.
TABLE I. TURBO CHARGE
On the subject of fertility — this time male
— caffeine can be used in vitro as an
effective sperm motility enhancer! Israeli IVF
trials found that using caffeine-treated
frozen-thawed sperm samples resulted in
twice the number of pregnancies compared
with non-caffeine-treated sperm[12].
Although the drug of preference for in
vitro sperm treatment these days is
pentoxifylline, caffeine gives a similar "turbo
charge", to quote Peter Brindson, Medical
Director of Bourn Hall IVF clinic in
Cambridgeshire.
So, given that a vast array of (often
contradictory) data is available on coffee,
what does it all really say about the health
effects of coffee and caffeine?
COFFEE AND HEALTH
One question which is raised fairly frequently
concerns the effects of coffee drinking on
pregnancy. The Royal College of Midwives
advises that a pregnant or breastfeeding
woman can, without concern, drink up to
four or five cups of tea or coffee per day if
she wishes. This is in agreement with the
results of the bulk of research[9] — after
sorting through the sometimes conflicting
epidemiological data.
For example, consider one particular
published paper which suggested that
29

3. NUTRITION &
FOOD SCIENCE
PROTECTIVE EFFECT
On the contrary, research consistently shows
an inverse association between coffee
drinking and colorectal cancer[19]. Although
no biological mechanism for the protective
effect has yet been put forward, the results
seem convincing, and further studies are
continuing.
CARDIAC CONCERNS?
The potential relationship between coffee
drinking and cardiovascular disease,
myocardial infarction, cardiac arrhythmias,
high blood pressure, and raised serum
cholesterol are other commonly debated
subjects, and have been extensively
investigated.
Again, findings overall have shown that
coffee drinking is not a risk factor for any of
these conditions, and the British Heart
Overall, human epidemiological studies of Foundation states that it "does not believe
maternal coffee drinking do not provide that coffee increases the risk of heart
evidence of adverse effects on any aspect of disease".
reproduction, including low birthweight,
preterm birth, or congenital Especially relevant are the consistently
malformations[9]. Furthermore, although negative findings from the longer-runnng,
caffeine does diffuse into breast milk after larger epidemiological studies[20], while
maternal consumption, it is not present in interventional trials on the effects of
significant quantities, and moderate coffee coffee/caffeine on serum cholesterol, blood
drinking should not have any effects on a pressure, and cardiac arrhythmias have also
breastfeeding infant[13,14] — a fact which is shown no adverse effects whatsoever.
in accord with Royal College of Midwives' Most recently, for example, MacDonald's
advice. study showed through 24-hour ambulatory
blood pressure monitoring, that including or
GETTING THE PICTURE
The greater number of papers one does look
at, the more evident it becomes that
moderate amounts of coffee and caffeine
have no adverse effects on any aspect of
health for the general population. This is
borne out by a variety of published reviews.
For example, the American Cancer Society's
Guidelines on Diet, Nutrition, and Cancer,
conclude that "Available information does
not suggest a recommendation against its
[coffee's] moderate use. There is no
indication that caffeine . . . is a risk factor
in human cancer"[15].
Although for one particular site — bladder
cancer — there has been a certain amount of
concern in the past, many studies on this
topic have actually found no association
whatsoever with coffee drinking, while others
show no dose-response relationship, and are
not suggestive of a causal association[16-18].
30

4. NUMBER 1
JANUARY/FEBRUARY 1993
(see "Caffeine's Actions"). These are known
to have beneficial effects on concentration
and alertness, especially at times of natural
lows such as during night-shift work, or after
lunch during the early to mid afternoon
period[29,30]. But caffeine also increases the
body's lipolytic (fat burning) rate, which has
potential benefits (albeit minor) for people
trying to lose weight[31].
The effects of caffeine on fat burning may
not be great, but research does suggest that
moderate amounts of coffee could help the
body burn up the equivalent of 80-100
calories a day[32]. And of course, coffee
(using skimmed milk and no sugar) is
virtually calorie-free.
A LITTLE BIT OF WHAT YOU FANCY . . .
Everyone tends to find their own comfortable
level of drinking coffee. This can vary greatly
between individuals. While the research does
excluding caffeine from the diets of mild
show that drinking coffee is not associated
hypertensives has absolutely no effect on
with adverse health effects, some people are
their blood pressures whatsoever[21].
particularly sensitive to the caffeine stimulant.
SCANDINAVIAN CONNECTION □
The link between coffee and cholesterol
makes a particularly neat and conclusive NO-ONE WHO ENJOYS DRINKING
story. During the 1980s, studies from Norway COFFEE SHOULD BE CONCERNED
found an association between coffee drinking ABOUT ITS HEALTH EFFECTS
and raised cholesterol levels[22,23].
Many subsequent investigations have □
conclusively shown that the effect is due to
the type of coffee commonly consumed by They may, for example, prefer to drink
people in this geographical area[24]. Only decaffeinated rather than caffeinated coffee
this speciality Scandinavian coffee — in the evening for their ease of getting to
prepared by prolonged boiling of coffee sleep. Similarly, a few caffeine-sensitive
grounds in water and decanting without people with cardiac problems may be advised
filtering — has been found to raise blood to limit their caffeine intake, and switch to
cholesterol levels. decaffeinated coffee.
All other types of coffee studied (including This may not generally be necessary,
drip-filtered, instant, and decaffeinated) have however, as a recently published analytical
been shown to have no effects whatsoever on review of past research has shown that even
cholesterol[25,26]. patients in coronary care units can be
The cholesterol-raising factor in "boiled" allowed to drink four or five cups of coffee
coffee is not caffeine, but resides in a lipid- per day without it increasing the likelihood
rich fraction isolated from the brew[27], and of cardiac arrhythmias[33]. Indeed, another
can be removed from the coffee simply by recent review summarizes the findings of
filtering the brew through a paper filter[28]. coffee/caffeine and cardiovascular research,
Indeed, drinking boiled coffee which has with the conclusions: "There is no
been paper-filtered before consumption has association between coffee consumption and
no elevating effects on blood cholesterol[28]. the occurrence of coronary heart
disease. . .Focusing attention on life-style
FIGHT AGAINST FAT factors not implicated as causative of CHD
The caffeine in a cup of coffee is best may only serve to frustrate valid health
recognized for its mildly stimulant properties promotional efforts"[34].
31

5. NUTRITION &
FOOD SCIENCE
As people all react differently to caffeine, 9. Leviton, A., "Caffeine Consumption and the
decaffeinated coffees are available not so Risk of Reproductive Hazards", Journal of
much as a "healthier" alternative to Reproductive Medicine, Vol. 33 No. 2, 1988,
caffeinated varieties, but simply so that pp. 176-8.
anyone who is particularly sensitive to
10. Wilcox, A., Weinberg, C. and Baird, D.,
caffeine can continue to enjoy their coffee.
"Caffeinated Beverages and Decreased
The overall bulk of research suggests that
Fertility", The Lancet, 24/31 December 1988,
no one who enjoys drinking coffee should be
pp. 1453-5.
concerned about its health effects, or abstain
from coffee because of unfounded worries 11. Joesoef, M.R., Beral, V., Rolfs, R.T., Aral, S.O.
about either coffee itself, or caffeine. and Cramer, D.W., "Are Caffeinated Beverages
Risk Factors for Delayed Conception?" The
Lancet, Vol. 335, 1990, pp. 136-7.
12. Barkay, J., Bartoov, Ben-Ezra, S., Langsam, J.,
Feidman, G., Gordon, S. and Zuckerman, H.,
"The Influence of In Vitro Caffeine Treatment
References on Human Sperm Morphology and Fertilizing
Capacity", Fertility and Sterility, Vol. 41 No. 6,
1. Kaplan, G.B., Greenblatt, D.J., Kent, M.A. and
1984, pp. 913-8.
Cotnear, M.M., "Caffeine-induced Behavioural
Stimulation Is Dose-dependent and Associated 13. Tyrala, E.E. and Dodson, W.E., "Caffeine
with A1 Adenosine Receptor Occupancy, Secretion into Breast Milk", Archives of
Neuropsychopharmacology, Vol. 6 No. 3, Diseases of Childhood, Vol. 54, 1979, pp.
1992, pp. 145-153. 787-800.
2. Dews, P.B., "Caffeine", Annual Review of 14. Berlin, C.M., Denson, H.M., Daniel, C.H. and
Nutrition, Vol. 2, 1982, pp. 323-41. Ward, R.M., "Disposition of Dietary Caffeine in
3. Bättig, K., "The Physiological Effects of Coffee Milk, Saliva, and Plasma of Lactating Women",
Consumption", Chapter 15, in Clifford, M.N. Paediatrics, Vol. 73, 1984, pp. 59-63.
and Wilson, H.C. (Eds) Coffee Botany, 15. The Work Study Group on Diet, Nutrition and
Biochemistry and Production, 1985. Cancer, "American Cancer Society Guidelines
4. Laska, E.M., Sunshine, A., Mueller,F.,Elvers, on Diet, Nutrition and Cancer", CA-A Cancer
W.B., Siegel, C. and Rusin, A., "Caffeine as an Journal for Clinicians, Vol. 41 No. 6, 1991, pp.
Analgesic Adjuvant", Journal of the American 334-7.
Medical Association, Vol. 251 No. 13, 1984, 16. Jensen, O.M., Wahrendorf, J., Knudsen, J.B.
pp. 1711-8. and Sorensen, B.L., "The Copenhagen Case-
5. Schachtel, B.P., Fillingham, J.M., Lane, A.C., control Study of Bladder Cancer, II. Effect of
Thoden, W.R. and Raybutt, R.I., "Caffeine as Coffee and Other Beverages", International
an Analgesic Adjuvant. A Double-blind Study Journal of Cancer, Vol. 37, 1986, pp. 651-7.
Comparing Aspirin with Caffeine to Aspirin
17. Ciccone, G. and Vineis, P., "Coffee Drinking
and Placebo in Patients with Sore Throat",
and Bladder Cancer", Cancer Letters, Vol. 41,
Archives of Internal Medicine, Vol. 151, 1991,
1988, pp. 45-52.
pp. 733-7.
18. Morrison, A.S., "Geographic and Time Trends
6. Ward, N., Whitney, C, Avery, D. and Dunner,
of Coffee Imports on Bladder Cancer",
D., "The Analgesic Effects of Caffeine in
European Journal of Cancer, Vol. 14, 1978, pp.
Headache", Pain, Vol. 44, 1991, pp. 151-5.
51-4.
7. Fuglsang, G., Nielsen, K., Nielsen, L.K.,
Sennels, F. and Jakobsen, P., "The Effect of 19. La Vecchia, C., Ferraroni, M., Negri, E.,
Caffeine Compared with Theophylline in the D'Avanzo, B., Decarli, A., Levi, F. and
Treatment of Idiopathic Apnea in Premature Franceschi, S., "Coffee Consumption and
Infants", Acta Paediatrics Scandinavia, Vol. 78, Digestive Tract Cancers, Cancer Research, Vol.
1989, pp. 786-8. 49, 1989, pp. 1049-51.
8. Amato, M., Isenschmid, M. and Huppie, P., 20. Dawber, T.R., Kannel, W.B. and Gordon, T.,
"Percutaneous Caffeine Application in the "Coffee and Cardiovascular Disease:
Treatment of Neonatal Apnoea", European Observations from the Framingham Study",
Journal of Paediatrics, Vol. 150, 1991, pp. New England Journal of Medicine, Vol. 291,
592-4. 1974, pp. 871-4.
32

6. NUMBER 1
JANUARY/FEBRUARY 1993
21. MacDonald, T.M., Sharpe, K., Fowler, G., 29. Smith, A.P., Rosted, J.M., Eaton-Williams, P.,
Lyons, D., Freestone, S., Lovell, H.G., Webster, Savory, M. and Leathwood, P., "Effects of
J. and Petrie, J.C., "Caffeine Restriction: Effect Caffeine Given Before and After Lunch on
on Mild Hypertension", British Medical Journal, Sustained Attention", Neuropsychobiology, Vol.
Vol. 303, 1991, pp. 1235-8. 23, 1990, pp. 160-3.
22. Thelle, D.S., Arnesen, E. and Forde, O.H., "The 30. Walsh, J.K., Muehlbach, M.J., Humm, T.M.,
Tromso Heart Study: Does Coffee Raise Serum Stokes Dickens, Q., Sugarman, J.L. and
Cholesterol?" New England Journal of Schwitzer, P., "Effect of Caffeine on
Medicine, Vol. 308, 1983, pp. 1454-7. Physiological Sleep Tendency and Ability to
23. Thelle, D.S., Forde, O.H., Knutsen, S.F. and Sustain Wakefulness at Night",
Arnesen, E., "The Tromso Heart Study: Coffee Psychopharmacology, Vol. 101, 1990, pp.
Consumption and Serum Lipid Concentrations 271-3.
in Men with Hypercholesterolaemia: A 31. Hollands, M.A., Arch, J.R.S. and Cawthorne,
Randomised Intervention Study," British M.A., "A Simple Apparatus for Comparative
Medical Journal, Vol. 290, 1985, pp. 893-5. Measurements of Energy Expenditure in
24. Bak, A.A.A. and Grobbee, D.E., "The Effect on Human Subjects: The Thermic Effect of
Serum Cholesterol Levels of Coffee Brewed By Caffeine", American Journal of Clinical
Filtering or Boiling", New England Journal of Nutrition, Vol. 34, 1981, pp. 2291-4.
Medicine, Vol. 321, 1989, pp. 1432-7. 32. Dulloo, A.G., Geissler, C.A., Horton, T., Collins,
25. Rosmarin, P.C., Applegate, W.B. and Somes, A. and Miller, D.S., "Normal Caffeine
G.W., "Coffee Consumption and Serum Lipids: Consumption: Influence on Thermogenesis and
A Randomized, Crossover Clinical Trial", Daily Energy Expenditure in Lean and
American Journal of Medicine, Vol. 230, 1990, Postobese Human Volunteers", American
pp. 293-7. Journal of Clinical Nutrition, Vol. 49, 1989, pp.
26. Burr, M.L., Gallacher, J.E.J., Butland, B.K., 44-50.
Bolton, C.H. and Downs, L.G., "Coffee, Blood 33. Lynn, L.A. and Kissinger, J.F., "Coronary
Pressure and Plasma Lipids: A Randomized Precautions: Should Caffeine Be Restricted in
Controlled Trial", European Journal of Clinical Patients after Myocardial Infarction?", Heart &
Nutrition, Vol. 43, 1989, pp. 477-83. Lung, Vol. 21, 1992, pp. 365-70.
27. Katan, M.B., Zock, P.L., Merkus, M.P., van 34. Myers, M.G. and Basinski, A., "Coffee and
Dusseldorp, M, and Harryvan, J.L., "Effect of a Coronary Heart Disease", Archives of
Lipid-rich Fraction from Boiled Coffee on International Medicine, Vol. 152, September
Serum Cholesterol", The Lancet, Vol. 335, 1992, pp. 1767-72.
1990, pp. 1235-7.
28. Katan, M.B., van Dusseldorp, M., van Vliet, T.,
Demacker, P.N.B. and Stalenhoef, A.F.H., "The
Cholesterol-raising Factor from Boiled Coffee Sophia Papadopoulos is a Science Writer
Does Not Pass a Paper Filter", Arteriosclerosis based at the Coffee Science Information
and Thrombosis, Vol. 11 No. 3, 1991, pp. Centre, Little Tew, Oxon.
586-94.
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