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Memory
Research from Johns Hopkins University suggests that a dose of caffeine after a learning session may help boost long-term memory.
It has been suggested that caffeine enemas may help prepare the colon for an endoscopy or colonoscopy by supporting the excretion of bile through the colon wall.
Proponents claim that a caffeine enema increases the levels of glutathione, an antioxidant, and so it supports the natural processes of detoxification in the liver.
However, there is little evidence to support this theory.
Coffee consumption may help decrease the risk of cirrhosis and slow the rate of disease progression in hepatitis C infection. Observational studies have found that coffee may have protective benefits for people with hepatocellular cancer.
Menopause
A study published in the journal Menopause found that women who consumed caffeine during menopause were more likely to have hot flashes and night sweats.
Caffeine’s main effect on the body is an increased temporary sense of wakefulness and alertness, but it can also cause uncomfortable symptoms.
Consuming over 400 mg of caffeine a day can lead to:
- jitters and shakes
- disrupted sleep
- fast or uneven heartbeat
- high blood pressure
- headaches
- nervousness or anxiety
- dizziness
- dependency
- dehydration
- irritability
- heartburn
- stomach upset, diarrhea, and nausea
- muscle tremors
Caffeine increases the release of acid in the stomach, sometimes leading to an upset stomach or heartburn.
Caffeine can interfere with the sleep cycle. Sleep loss is cumulative, and even small nightly decreases can add up and disturb daytime alertness and performance.
Type 2 diabetes
One longitudinal study found that participants who increased their coffee intake by more than one cup a day over a 4-year period had a 1 percent lower risk of developing type 2 diabetes compared with people who did not change their intake.
People who lowered their daily consumption by more than one cup of coffee showed a 17 percent higher risk for type 2 diabetes.
A study published in Diabetes Care in 2004 linked a high coffee consumption over a period of 4 weeks with increased fasting insulin concentrations.
However, the reasons for the link were unclear. It may be due to lowered insulin sensitivity, meaning the body does not use the insulin produced efficiently.
Much of the published research about caffeine suggests that it is beneficial, in moderation.
However, some studies highlight the potentially harmful effects of caffeine.
FACTORS AFFECTING CAFFEINE METABOLISM
Caffeine metabolism is increased by smoking, an effect mediated by an acceleration in its demethylation (it also increases xanthine oxidase activity) (Parsons and Neims, 1978). Smoking cessation returns caffeine clearance rates to nonsmoking values (Murphy et al., 1988). A number of studies with rodents have demonstrated an additive effect of caffeine and nicotine on both schedule-controlled behavior and locomotor activity (Lee et al., 1987, Sansone et al., 1994, White, 1988). However, data in humans are scarce. Kerr et al. (1991) found both caffeine and nicotine facilitated memory and motor function in a variety of psychomotor tasks. Though there were differences across tasks, combining caffeine and nicotine did not appear to produce a greater effect than either drug alone. Conversely, nicotine did not decrease the effectiveness of caffeine.
The effects of caffeine on women have been examined in the context of its effects on menstrual function, interactions with oral contraceptives, pregnancy and fetal health, and postmenopausal health. Earlier studies suggested that elimination of caffeine may vary across the menstrual cycle, with elimination being about 25 percent longer in the luteal phase (Balogh et al., 1987). More recent studies, however, indicate no significant effects on caffeine pharmacokinetics across phases of the menstrual cycle in healthy, nonsmoking women who are not using oral contraceptives (Kamimori et al., 1999). Decreased paraxanthine or caffeine metabolic rates in healthy postmenopausal women on estrogen replacement therapy suggest that exogenous estrogen in older women may inhibit caffeine metabolism through the P450 isozyme CYP1A2, an isozyme common to both estrogen and caffeine metabolism (Pollock et al., 1999). Additionally, it is known that oral contraceptive use can double caffeine half-life (Abernethy and Todd, 1985, Patwardhan et al., 1980). The effects of newer oral contraceptives on caffeine half-life have not been studied.
