VOL: 96, ISSUE: 40, PAGE NO: 7
Ray Addison, BSc, RN, FETC, CertHEd, is nurse consultant, bladder and bowel dysfunction, Mayday Healthcare NHS Trust, Croydon
Caffeine is the most widely consumed behaviour-modifying drug in the world. It occurs naturally in about 60 species of plants, most commonly in coffee beans, tea leaves, cocoa seeds and the cola nut (Thomas, 1990; Greener, 1993).
Social consumption of coffee, tea and cola or energy-boosting soft drinks is the most common source of caffeine, although decaffeinated versions of these drinks are becoming increasingly popular in the developed world.
Caffeine is also found in a range of over-the-counter analgesic medications, which must be included when calculating a patient’s daily caffeine consumption.
Caffeine is a stimulant that gets into the bloodstream within minutes, increasing the blood pressure and respiratory rate. It improves muscle strength, constricts blood vessels in the brain, reduces fatigue and boosts vigilance (Leonard et al, 1987; Greener, 1993).
Caffeine has a half-life of about five hours. It interacts with a number of medicines, including diazepam and cimetidine, but this is not thought to be hazardous (Greener, 1993). The excretion of caffeine is slower during pregnancy and in people with liver disease, those taking oral contraceptives and smokers (Leonard et al, 1987).
There is debate over a link between caffeine and heart disease and cancer (Thomas, 1990), but cardiac arrythmias and palpitations have been linked to caffeine intake (Leonard et al, 1987; Greener, 1993).
Caffeine and the bowel
Most research on caffeine and bowel function has looked specifically at coffee. Wald et al (1976) found that coffee has a laxative effect. This was confirmed when later studies showed that coffee stimulates colonic motor and bowel activity (Brown et a1, 1990; Addison, 1999).
This motor response occurs within minutes of drinking coffee and can last for up to 90 minutes. There is no gender difference in the effect that coffee has on motor activity (Rao et al, 1998), but it may not be related to caffeine. Brown et al (1990) state that decaffeinated coffee has the same effect on bowel activity, although Rao et al (1998) believe it may be less potent.
Wald et al (1976) suggest that caffeine increases the secretion of fluid in the small intestine, but this does not increase total gut transit time (Addison, 1999).
In terms of stimulating the gastrocolic reflex, coffee has the same effect on digestive function as eating a meal, but its effect is of shorter duration (Rao et al, 1998).
Coffee is also known to cause heartburn, dyspepsia and ulcers and to aggravate the symptoms of inflammatory bowel syndrome, especially in women (Brown et al, 1990; Cohen,1980).
Implications for patients
So what are the implications of the effects of coffee on bowel activity? In patients with slow-gut-transit constipation, coffee could maintain or improve bowel function (Rao et al, 1998). But for patients with diarrhoea or faecal continence problems, the best advice may be to stop drinking it (Rao et al, 1998).
Nurses must also bear in mind that decaffeinated coffee can have the same effect on bowel function as caffeinated coffee.
Patients who are involved in any form of gut motility study should have their intake of caffeine and other drugs checked, including over-the-counter medications, as these may have a bearing on the results.
Caffeine and bladder function
Caffeine has a diuretic effect, which increases urine output (Leonard et al, 1987) and could contribute to dehydration. Creighton and Stanton (1990) found that it increases urgency and frequency in patients with proven detrusor instability. Urethral pressure may be reduced by caffeine, which could also increase the risk of stress incontinence (Palermo and Zimskind, 1977).
Caffeine may reduce sleeping times and depth of sleep (Leonard et al, 1987; Greener, 1993), which may indirectly increase nocturia. And some patients with cystitis find that coffee and caffeine irritate the bladder.
Although most people become tolerant of the effects of caffeine and are not addicted to it, Thomas (1990) suggests a maximum daily intake of about six cups/four mugs of coffee.
Withdrawal symptoms are common when cutting down on or giving up caffeine. These include headaches, drowsiness, stomach upsets, irritability, depression, nausea, nervousness, muscle pains, sweating, a runny nose, feelings of fullness in the head and tremor (Thomas, 1990; Greener, 1993). Health care practitioners should advise patients to reduce their caffeine intake gradually to minimise these effects.
Giving up or restricting caffeine intake is recommended during pregnancy and women should restrict themselves to one cup of coffee a day when breastfeeding (Greener, 1993). A low intake of caffeine is also recommended for people with hypertension, kidney disease, high cholesterol levels or heart disease (Leonard et al, 1987; Thomas, 1990).
If decaffeinated drinks are used, ensure that the caffeine has not been extracted using a chemical method (Thomas, 1990). Chemical extraction has been associated with health risks and it is advisable to select a brand that uses water or carbon dioxide to extract the caffeine.
Nurses should also be aware that patients, particularly those who are prone to food allergies, can develop allergies to coffee and tea (Leonard et al, 1987).
Nurses have an important role to play in assessing patients’ consumption of coffee and caffeine and investigating and associating any effects on their health.
The nursing implications are summarised in Table 1. Patients should be offered appropriate advice on caffeine intake, supported by written information.