Caffeine and health related issues

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Caffeine is one of the most comprehensively studied ingredients in the food supply. (7) We consume caffeine from variety of sources – primarily coffee, tea, chocolate, cocoa, some soft drinks, and both prescription and non-prescription drugs.

Caffeine Molecule

       

Caffeine can be found in many drinks, food and drugs. The following items all contain various amounts of caffeine. (8)

Caffeine is a central nervous system stimulant and belongs to the xanthine chemical group. It enters the bloodstream through the stomach and small intestine, where it takes about 15 - 45 minutes to reach peak level. The level of caffeine in the blood reaching the brain determines the potency of its effects on the body. Usually the central nervous system is maximally stimulated within 30 – 60 minutes. (5) Caffeine is metabolised by the liver and eventually its metabolites are excreted in urine, although can be secreted in saliva, semen, and breast milk. (5)

Caffeine will continue to have an effect on the body as long as it remains in the blood. The time required for the body eliminate one-half of the total amount of caffeine consumed (or caffeine’s half-life) varies from several hours to several days, but for the average non-smoking adult is about 5-7 hours. Several factors can lengthen caffeine’s half-life, such as some medications, liver diseases, pregnancy, and the level of enzymes in the liver needed for caffeine metabolism. The half-life of caffeine in pregnant women is 18-20 hours; the half-life in women taking oral contraceptives is up to 13 hours. Other factors, such as smoking and age can shorten caffeine’s half-life e.g. in children and smokers averages about 3 hours. (5)

Caffeine stimulates the central nervous system and can produce a variety of effects elsewhere in the body e.g. increases heartbeat, respiration, basal metabolic rate, and the production of stomach acid and urine; and it relaxes smooth muscles, notably the bronchial muscle. (5) It can also upset the hormone levels in the body, in particular insulin and glucagons, which regulates blood sugar, inhibit the absorption of vitamins and minerals from the gut. (2) All of these changes vary considerably among people and may depend upon the individual’s sensitivity to the caffeine, his/her metabolism, or upon whether the consumer habitually uses or rarely uses caffeine. (5) Level of caffeine for the average adult is approximately 200 mg daily. The average child consumes much less caffeine – only one-quarter of the caffeine consumed by adults. (3) Larger doses of caffeine, especially when given to non-users can produce headache, jitteriness, abnormally rapid heartbeat, convulsions, and even delirium. Near fatal doses a cause crisis resembling the state of a diabetic without insulin, including high levels of blood sugar and the appearance of acetone-like substances in urine. The lowest known dose fatal to an adult has been 3,200 mg – administered intravenously by accident. The fatal oral dose is in excess of 5,000 mg – the equivalent of 40 strong cups of coffee taken in a very short space of time. (6) The symptoms of a caffeine overdose will also vary, according to individual differences and the amount consumed. Doses ranging from 250 to 750 mg (2 to 7 cups of coffee) can produce restlessness, dizziness nausea, headache, tense muscles, sleep disturbances, and irregular heart beats. Doses over 750 mg (7 cups of coffee) can produce all of the above as well as a reaction similar to an anxiety attack, including delirium, drowsiness, ringing ears, diarrhoea, vomiting, light flashes, difficulty breathing, convulsions (extreme overdose). These amounts of caffeine may come from a single dose or from multiple doses at short intervals. Besides caffeine’s effects, the essential oils of coffee may cause gastrointestinal irritation and diarrhoea, and the high tannin content of tea can result in constipation. (5)

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Regular use of upwards of 350 mg of caffeine a day causes physical dependence on the drug. This means that interruption of the regular use produces a characteristic withdrawal syndrome, the most conspicuous feature of which is an often severe headache that can be relieved by taking caffeine. Absence of caffeine also makes regular uses feel irritable and tired. (6)

Caffeine and health problems.

 Heartburn – in some people, coffee has been shown to relax the sphincter muscles at the lower and of the oesophagus, allowing the stomach contents to “back up” into the oesophagus: this is called ...

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