Physiological Effects of Caffeine 

Physiological Effects of Caffeine: (Note that the doses of caffeine required to produce such effects, and the severity of those effects, varies between individuals.)


(-) Caffeine is a vasoconstrictor and stimulant.

(-) Caffeine often increases blood pressure by contracting the heart and blood vessels in non-habitual users. Effects usually subside after 3 4 h.

(-) Caffeine changes the electro-physiological activity of the heart, increasing conductivity, even in limited doses.

(-) Heavy caffeine consumption raises (by about 2 mmol/L)the plasma levels of homocystine, a risk factor for heart disease.

(-) Caffeine raises plasma epinephrine and norepinephrine levels in non-habitual users.

(-) Coffee intake may raise serum cholesterol levels. Intakes of 5+ cups of unfiltered have been shown to raise cholesterol levels by 0.5 1.0 mmol/L (20 40 mg/dL).


(-) Caffeine stimulates gastric secretion. Some individuals are sensitive to caffeine and suffer ill effects such as acid indigestion, heartburn, abdominal pain, gas or constipation to varying degrees.

(-) Coffee can cause emesis (vomiting)

(-) Caffeine inhibits vassopressin, it acts as a powerful diuretic (it increases urination.)

(-) Liver metabolism is effected by methylxanthines such as caffeine. It increases the levels of cyclic AMP and decreases the level of branched chain and aromatic amino acids in plasma.


(-) Caffeine can mobilize calcium from cells and may lead to bone mass loss.

(-) Caffeine consumption is a risk factor for osteoporosis.

(-) Caffeine affects skeletal muscle contractility.

(-) Tremor is a common side effect of caffeine consumption.


(-) Caffeine, particularly in doses of 300mg (3 cups of coffee) or more per day, can result in both male and female infertility.

(-) In animal tests, high caffeine consumption was associated in poor pregnancy outcome: spontaneous abortion, congenital malformations, fetal growth retardation, and residual effects in the newborn.


(-) Caffeine stimulates respiration. This effect is mediated by the neurotransmitters dopamine and seratonin.

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