Caffeine gastrointestinal effects

Individual sensitivity to coffee drinking may or may not be related to its caffeine content. Other compounds found in coffee are probably responsible, as the same individuals can often drink tea without adverse gastrointestinal effect. 

A much milder and legal stimulant is caffeine, depicted in Figure 14.27. A number of mechanisms have been proposed for caffeines stimulatory effects. Perhaps the most straightforward mechanism is caffeine s facilitating of the release of norepinephrine into synaptic clefts. Caffeine also exerts many other effects on the body, such as dilation of arteries, relaxation of bronchial and gastrointestinal muscles, diuretic action on the kidneys, and stimulation of stomach-acid secretion. 

Coffee causes nervousness, tremors, insomnia, and gastric symptoms withdrawal symptoms —With excessive coffee intake, some individuals develop untoward nervous system effects from caffeine, such as nervousness, tremors, and insomnia. In rare cases, there may be gastric symptoms such as heartburn, abdominal discomfort, or diarrhea but generally such gastrointestinal effects occur with excessive coffee consumption. Also, some experience headaches with the withdrawal of caffeine, beginning about 12 to 15 hours after the last dose of caffeine. 

Caffeine stimulates gastric secretion. Other factors in coffee besides caffeine also cause increase gastric secretion. This is probably the most striking effect of coffee on the gastrointestinal tract. 

Caffeine is a powerful stimulant of central nervous system and also stimulates the cardiac muscle. However, high amounts of the alkaloid have noticeable irritation of gastrointestinal tract as well causes matw unwanted effects [1]. 

Johnston, K.L., Clifford, M.N., and Morgan, L.M., Coffee acutely modifies gastrointestinal hormone secretion and glucose tolerance in humans glycemic effects of chlorogenic acid and caffeine. Am. J. Clin. Nutr., 78, 728, 2003. 

Some people find that caffeine irritates their gastrointestinal tract. It is still unclear if the effect is from caffeine itself, or from another as-yet-undetermined substance that could be in coffee. Regardless, people with stomach ulcers or irritation may not find relief by switching from caffeinated to decaffeinated coffee. 

Throughout the past 100 years, numerous investigations have examined the pharmacological effects of caffeine on metabolism, cardiovascular, respiratory, gastrointestinal, renal, and CNS functioning in humans. These studies have con-... 

Ephedrine, synephrine, and caffeine are all well absorbed from the gastrointestinal tract, hollowing ingestion of an oral dose, clinical effects are seen within 60 min and persist from 2 to 6 h. Ephedrine is metabolized in the liver by oxidative deamination, demethylation, aromatic hydroxylation, and... 

Most preparations contain low doses, although they may be sufficient to add to gastrointestinal adverse effects. Caffeine is also habit-forming and may itself induce headache in large doses or on withdrawal. 

Caffeine is a stimulant of the central nervous system. It eliminates fatigue and drowsiness. However, high doses cause gastrointestinal motility, restlessness, sleeplessness, nervousness, and tremor. Acute poisoning effects include nausea, vomiting, headache, excitability, tremor, and sometimes, convulsive coma. Other symptoms may be respiratory depression, muscle contraction, distorted perception, and hallucination. Ingestion of 15-20 g may be fatal to humans. 

Caffeine relaxes smooth muscle of the biliary and gastrointestinal tracts and has a weak effect on peristalsis. However, high doses can produce biphasic responses, with an initial contraction followed by relaxation. Caffeine seems to have no effect on the lower oesophageal sphincter. The increase in both gastric and pepsin secretions is linearly related to the plasma levels obtained after the administration of a dose of 4-8mgkg . In the small intestine, caffeine modifies the fluid exchange from a net absorption to a net excretion of water and sodium. 

Caffeine and theophylline are methylxanthine derivatives that are widely distributed in plant products and beverages. Theophylline and caffeine have been widely used for the treatment of asthmatic manifestations, neonatal apnea and bronchial spasms. However, these compounds produce the biological effect of dieresis, and excessive intake leads to many undesired side effects, with symptoms including tremors, excessively fast heartbeat and gastrointestinal difficulties [35]. Therefore, it is very important to determine accurately the content of these alkaloids in foods and pharmaceutical preparations. 

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