About what percentage of people regularly drink tea or coffee?
80-90%
What is the average adult daily intake of caffeine?
200-400mg
How is caffeine consumed in children?
Through chocolate and soft drinks.
How is caffeine absorbed and how long does it take?
Through the gastrointestinal tract, over about 30-60mins.
What is the plasma half-life of caffeine?
Around 4 hours, but people’s concentration in blood plasma tends to rise over the day - top ups.
What is caffeine converted to in the liver?
Metabolites.
How is caffeine excreted?
95% in urine, 2-5% in faeces, the rest through saliva.
What are the behavioural effects of caffeine?
Arousal.
- Smith et al (1999) found that low-intermediate doses have a variety of positive subjective effects when taken after 24hrs abstinence.
What is meant by the effect of caffeine being biphasic?
At low doses it’s a stimulant that increases locomotor activity, but at high doses it does the opposite.
What did Rogers and Dernoncourt (1998) suggest about the positive effects of caffeine after abstinence?
That they might be an alleviation of withdrawal symptoms.
What did Griffiths and Mumford (1995) find about caffeine tolerance?
That people develop tolerance to the subjective effects of caffeine, e.g. heavy drinkers can consume coffee before bed.
What did Griffiths et al (1990) find about withdrawal symptoms in caffeine drinkers?
That it occurs even in people who only drink one cup a day.
What are the health effects of chronic caffeine consumption?
- High BP
- Risk of coronary heart disease
- Low infant birth weight.
