Health effects of caffeine
Encyclopedia
The health effects of caffeine have been extensively studied. Short term side effects such as headache
, nausea
, and anxiety
have been shown as symptoms of mild caffeine
consumption. The long term consequences of moderate caffeine consumption can be reduced risk of developing Parkinson's disease
, type 2 diabetes, hepatic diseases, and cardiovascular disease. Caffeine competitively inhibits different adenosine receptors and their associated G protein to make a person feel alert. A mild stimulant of the central nervous system, caffeine also stimulates cardiac muscle, relaxes smooth muscle
, increases gastric secretions, and produces diuresis
.
In these studies, the greatest benefits were observed in those who drank coffee
for a long period in their lifetime.
Caffeine
is a methylxanthine and methylxanthines are known to have anti-inflammatory properties. This is due to the similarity in molecular structure to the nucleotide adenosine. Methylxanthines or sometimes known as xanthines have a heterocyclic ring with nitrogen included in the ring structure; they are derived from amino acids, are basic in nature, and can generally form water soluble salts. Caffeine blocks the action of adenosine by acting as a competitive inhibitor for the A1 and A2a adenosine receptor. With the initial absorption of caffeine occurring within 15 minutes the peak time of caffeine absorption is estimated at 45 minutes. Although varying in many studies the half-life of caffeine has been found to be around 5.2-6.8 hours for adults. However, the metabolic rate of caffeine absorption differs between each species.
Caffeine toxicity can present as a spectrum of clinical symptoms. Most of these originate in the central nervous and circulatory systems and can follow ingestion of 1g or more of caffeine. Insomnia, breathlessness and excitement progressing to mild delirium may be seen. Sensory disturbances, diuresis
, tachycardia
, extrasystoles, and elevated respirations as well as vomiting induced by potent gastric irritation can be present. Fatalities of caffeine poisoning are rare because the gastric irritation and vomiting develop before absorption of toxic amounts can occur. Normally, caffeine is rapidly and completely absorbed from the gastrointestinal tract with distribution in various tissues in approximate proportion to their water content. Convulsions result from the central stimulating effect with death caused by respiratory failure. Hyperglycemia
and ketonuria
associated with caffeine toxicity have been reported. These latter findings may be attributed to a stress reaction or the xanthine’s ability to mimic the metabolic effects of the cathecholamines including lipolysis, glycogenolysis and gluconeogenesis. An acute overdose of caffeine usually in excess of about 300 milligrams, dependent on body weight and level of caffeine tolerance, can result in a state of central nervous system over-stimulation called caffeine intoxication (DSM-IV 305.90), or colloquially the "caffeine jitters". The median lethal dose (LD50) given orally, is 192 milligrams per kilogram in rats. The LD50 of caffeine in humans is dependent on weight and individual sensitivity and estimated to be about 150 to 200 milligrams per kilogram of body mass, roughly 80 to 100 cups of coffee for an average adult taken within a limited time frame that is dependent on half-life. For additional information see: Caffeine
.
, dopamine, gamma amino butyric acid and serotonin. Adenosine also reduces spontaneous firing of neurons in many regions of the brain which produces sedation and has anticonvulsant activity. Caffeine releases norepinephrine, dopamine and serotonin
in the brain and increases circulating catecholamines consistent with reversal of the inhibitory effects of adenosine on these systems.
and correct irregular heartbeats. Caffeine stimulates the central nervous system first at the higher levels, resulting in increased alertness and wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination, and later at the spinal cord level at higher doses. Once inside the body, it has a complex chemistry, and acts through several mechanisms as described below:
Moreover, the additional epinephrine increases the secretion of the main gastric hormone gastrin, which will speed up gastric peristalsis and hypersecretion of gastric juice. Additional gastric acid will lead to acidic chyme going into the small intestine and cause intestinal injury. Therefore, it is not recommended for ulcer patients to drink too much coffee.
Although the ability for caffeine and theophylline to induce diuresis and natriuresis is well established, the mechanisms behind them are not well understood.
It has been suggested that inhibition of phosphodiesterases in the proximal tubule may contribute to the diuretic and natriuretic effects of methylxanthines. It has been noted that mice lacking the A1 receptor do not exhibit the diuresis and natriuresis typically elicited by the application of the methylxanthines caffeine or theophylline.
since the summer of 2000, no longer treats caffeine as a banned substance.
or panic attacks, caused by ingesting excessive amounts of caffeine is seen more often in consumers with panic disorders. However, panic attacks are most often misdiagnosed with caffeinism, which is virtually indistinguishable from severe chronic anxiety. Caffeinism is a condition caused by ingesting a great amount of caffeine that shows a constellation of symptoms including insomnia, restlessness, excitement, dieresis, and tremors. When examining whether caffeine consumption leads to anxiety and mood changes, it is important to assess the participator’s level of anxiety. It has been claimed that people tend to drink caffeine containing beverages more frequently when they feel nervous, jittery or anxious. In 1986, Shanahan and Huges did a study on whether other stressors are capable of influencing anxiety increased by caffeine intake. Results show that in a healthy individual, consuming 400 mg or more caffeine while performing a stressful task results in increasing anxiety. Generally speaking, increasing levels of anxiousness after caffeine intake are mostly found in consumers who have consumed an amount that would not normally be consumed by majority of consumers. Lower doses of caffeine intake have little effect on consumers’ state. In fact, small amount of caffeine consumption may reduce one’s anxiety level.
has been a controversial topic among scientists.
Caffeine consumption has been associated with a lower risk of diabetes mellitus type 2
. The majority of the studies on this topic were done on coffee. Test results indicate that consumers who drink at least three or more cups of either caffeinated or decaffeinated coffee every day show a decrease in the risk of type II diabetes. In Japan
, a recent study was done to examine the relationship between consumption of green, black, and oolong tea
s and the risk of diabetes; and it was found that caffeine containing beverages were associated with a decreased risk of type II diabetes. The mechanism responsible for this inverse relationship between caffeine containing beverage and the risk of diabetes includes basal energy expenditure, fat oxidation stimulation, glycogen
mobilization in muscles, and stimulation of increased lipolysis from peripheral tissues. Unfortunately, tolerance of caffeine can develop. Certain antioxidant
substances in these beverages also play roles in decreasing risks of diabetes. For example, epigallocatechin gallate
, present in green tea, helps by acting on insulin resistance and glucose metabolism.
Diabetes patients have trouble controlling their sugar level in their blood due to lack of insulin resistance hormone.
Alloxan
is a chemical that damages insulin-producing cells and creates conditions for diabetes.
Once in the human body, caffeine produces alloxan and either produces diabetes' conditions or worsens the existing diabetes.
(PD) is the degeneration of dopamine producing neurons. Dopamine producing neurons stimulate the motor cortex effecting motor control. Loss of dopamine produces loss of motor control skills, cognitive function, and autonomic nervous system.
Epidemiological studies have shown that the risk of developing PD decreases with increasing levels of caffeine intake. Caffeine binds to the adenosine receptor (A2aR) and indirectly prevents MPTP
(an experimental neurotoxin known to cause PD) from destroying dopamine producing neural cells thus preventing neural degeneration and loss of motor control.
. However, there is a lack of evidence for other beverages that contain caffeine. It has been difficult to prove the exact cause for caffeine and its interaction with reducing the risk of liver cirrhosis. In addition, there is other research that shows caffeine to have suppressive effects of Tumor necrosis factor-alpha (TNF-α) induced hepatitis but yet has no effect on Anti-Fas induced hepatitis. Since TNF-α is secreted by macrophages in response of lipopolysaccharide (LPS), and it functions as a apoptoic factors, there are two ways that caffeine could suppress the hepatitis (e.g. by suppressing the TNF-α production and suppress the TNF-α induced apoptosis). However, the specific mechanism is not clear.
, because it leads to the fluctuation of plasma sex hormones and sex hormone-binding globulin (SHBG) in women. Circulating estrogens and androgens are important factors in female cancer development. Recent studies show that in premenopausal women, there’s an inverse relationship between caffeine intake and total luteal and estradiol levels in the second half of the menstrual cycle, and also has a positive association with progesterone
levels. Theoretically speaking, lower estrogen levels helps protect against ovarian cancer, but more research needs to be done on this topic.
For postmenopausal women, increased caffeine consumption is associated with a higher level of sex hormone-binding globulin (SHBG), which reduces the estradiol and testosterone activity and decreases the risk of breast cancer.
One patient reported: I had symptoms such as the flue, slept day and night for several days. After that, I felt as walking in a fog, far away from life, and had difficulty doing anything. After about three months, the withdrawal symptoms had almost completely declined.
has not developed definitive advice for adolescents 13 and older because of insufficient data. Nonetheless, Health Canada suggests that daily caffeine intake for this age group be no more than 2.5 mg/kg body weight. This is because the maximum adult caffeine dose may not be appropriate for light weight adolescents or for younger adolescents who are still growing. The daily dose of 2.5 mg/kg body weight would not cause adverse health effects in the majority of adolescent caffeine consumers. This is a conservative suggestion since older and heavier weight adolescents may be able to consume adult doses of caffeine without suffering adverse effects. For the rest of the general population of healthy adults, Health Canada advises a daily intake of no more than 400 mg.
According to the US-based Waverly Health Center, three 8 oz cups of coffee (about 250 milligrams of caffeine) per day is considered an average or moderate amount of caffeine; ten 8 oz cups of coffee per day is considered an excessive intake of caffeine.
Relatedly, one study found that caffeine can be used to treat hyperkinetic children. The research showed 200–300 mg of caffeine has a similar effect to methylphenidate
in treating hyperkinetic impulse disorder. Moreover, the caffeine treatment did not show the side-effects caused by methylphenidate.
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
, nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, and anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
have been shown as symptoms of mild caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
consumption. The long term consequences of moderate caffeine consumption can be reduced risk of developing Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
, type 2 diabetes, hepatic diseases, and cardiovascular disease. Caffeine competitively inhibits different adenosine receptors and their associated G protein to make a person feel alert. A mild stimulant of the central nervous system, caffeine also stimulates cardiac muscle, relaxes smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
, increases gastric secretions, and produces diuresis
Diuresis
Diuresis may refer to:* Urine production, as an aspect of fluid balance* Excessive urine production - see polyuria* Immersion diuresis...
.
Positive effects
- High long-term consumption is associated with a lower risk of cardiovascular diseaseCardiovascular diseaseHeart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...
and diabetes. - Research is beginning to suggest that caffeine minimizes the cognitive decline associated with aging.
- Caffeine increases levels of neurotransmitters such as noradrenaline, acetylcholine, and dopamine.
- AcetylcholineAcetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
is associated with attention, concentration, learning, and memory but there is no conclusive evidence yet that caffeine has any effect on memory and cognitive function. - Low doses of caffeine show increased alertness and decreased fatigue.
- Caffeine has been shown to increase the metabolic rate.
- Caffeine may reduce the risk of developing cancerCancerCancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
and produce a delay in the average onset of cancer. - Caffeine may be associated with a reduced risk of Parkinson’s disease.
- Caffeine may lower the risk of developing type 2 diabetes.
- Caffeine may reduce certain kind of hepatic cancers.
In these studies, the greatest benefits were observed in those who drank coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...
for a long period in their lifetime.
Negative effects
- Caffeine can increase vasoconstrictionVasoconstrictionVasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
and blood pressure. - High blood pressure is associated with an increase in strokes, and cerebral vascular disease, which in turn increase the risk of multi-infarct dementiaMulti-infarct dementiaMulti-infarct dementia is one type of vascular dementia. Vascular dementia is the second most common form of dementia after Alzheimer's disease in older adults. Multi-infarct dementia is thought to be an irreversible form of dementia, and its onset is caused by a number of small strokes or...
. - Caffeine may reduce control of fine motor movements (e.g., producing shaky hands)
- Caffeine can stimulate urination.
- Caffeine can increase cortisol secretion, some tolerance is developed.
- High doses of caffeine can cause anxiety.
- Caffeine can contribute to increased insomniaInsomniaInsomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...
and sleep latency. - Caffeine withdrawal produces headache, fatigue and decreased alertness.
- Caffeine is addictive.
Chemical properties
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
is a methylxanthine and methylxanthines are known to have anti-inflammatory properties. This is due to the similarity in molecular structure to the nucleotide adenosine. Methylxanthines or sometimes known as xanthines have a heterocyclic ring with nitrogen included in the ring structure; they are derived from amino acids, are basic in nature, and can generally form water soluble salts. Caffeine blocks the action of adenosine by acting as a competitive inhibitor for the A1 and A2a adenosine receptor. With the initial absorption of caffeine occurring within 15 minutes the peak time of caffeine absorption is estimated at 45 minutes. Although varying in many studies the half-life of caffeine has been found to be around 5.2-6.8 hours for adults. However, the metabolic rate of caffeine absorption differs between each species.
Toxicity and intoxication
Diuresis
Diuresis may refer to:* Urine production, as an aspect of fluid balance* Excessive urine production - see polyuria* Immersion diuresis...
, tachycardia
Tachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
, extrasystoles, and elevated respirations as well as vomiting induced by potent gastric irritation can be present. Fatalities of caffeine poisoning are rare because the gastric irritation and vomiting develop before absorption of toxic amounts can occur. Normally, caffeine is rapidly and completely absorbed from the gastrointestinal tract with distribution in various tissues in approximate proportion to their water content. Convulsions result from the central stimulating effect with death caused by respiratory failure. Hyperglycemia
Hyperglycemia
Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
and ketonuria
Ketonuria
Ketonuria is a medical condition in which ketone bodies are present in the urine.It is seen in conditions in which the body produces excess ketones as an alternative source of energy. It is seen during starvation or more commonly in type I diabetes mellitus...
associated with caffeine toxicity have been reported. These latter findings may be attributed to a stress reaction or the xanthine’s ability to mimic the metabolic effects of the cathecholamines including lipolysis, glycogenolysis and gluconeogenesis. An acute overdose of caffeine usually in excess of about 300 milligrams, dependent on body weight and level of caffeine tolerance, can result in a state of central nervous system over-stimulation called caffeine intoxication (DSM-IV 305.90), or colloquially the "caffeine jitters". The median lethal dose (LD50) given orally, is 192 milligrams per kilogram in rats. The LD50 of caffeine in humans is dependent on weight and individual sensitivity and estimated to be about 150 to 200 milligrams per kilogram of body mass, roughly 80 to 100 cups of coffee for an average adult taken within a limited time frame that is dependent on half-life. For additional information see: Caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
.
Relationship between caffeine and adenosine
The predominate mechanism of action of caffeine is the antagonism of adenosine receptors. Adenosine is a locally released purine hormone that acts on different receptors (A1 and A2) that can increase or decrease cellular concentrations of cyclic AMP (cAMP). Adenosine inhibits adenyl cyclise via high affinity (A1) receptors and stimulates adenyl cyclise via low affinity (A2) receptors. Adenosine receptors are found throughout the body including the brain, in the cardiovascular, respiratory, renal and gastrointestinal system and in adipose tissue. Caffeine nonselectively blocks both adenosine receptors and competitively inhibits the actions of adenosine. Adenosine acts presynaptically to inhibit neuronal release of acetylcholine, norepinephrineNorepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...
, dopamine, gamma amino butyric acid and serotonin. Adenosine also reduces spontaneous firing of neurons in many regions of the brain which produces sedation and has anticonvulsant activity. Caffeine releases norepinephrine, dopamine and serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
in the brain and increases circulating catecholamines consistent with reversal of the inhibitory effects of adenosine on these systems.
How caffeine wards off drowsiness
Caffeine and other methylxanthine derivatives are also used on newborns to treat apneaApnea
Apnea, apnoea, or apnœa is a term for suspension of external breathing. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged...
and correct irregular heartbeats. Caffeine stimulates the central nervous system first at the higher levels, resulting in increased alertness and wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination, and later at the spinal cord level at higher doses. Once inside the body, it has a complex chemistry, and acts through several mechanisms as described below:
- Increased calcium uptake activating metabolic pathways and neural activity
- Activation of wake-promoting neurons
- Release of neurotransmitters producing excitation
- Release of glutamate producing anxiety
- Increased blood flow to smooth muscles and vasoconstriction
- Inhibition of dopamine reuptake
- Inhibition of gamma-aminobutyric acidGamma-aminobutyric acidγ-Aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system...
(GABA) and excitation of the CNS - Inhibition of sleep promoting neurons
- Increased ATP production through cyclic adenosine monophosphateCyclic adenosine monophosphateCyclic adenosine monophosphate is a second messenger important in many biological processes...
(cAMP) accumulation - Increased motor activity
Cardiovascular
Caffeine increases cardiac arrhythmia (improper heart rate) by increasing stress hormone (e.g.adrenaline) secretions. It has been shown there is an increase in brachial diastolic blood pressure, but not in brachial systolic blood pressure. However, both aortic systolic and diastolic blood pressures increase significantly during caffeine consumption. It has been noted that long term consumption leads to increasing aortic systolic pressure which leads to chronic arterial stiffness. The results of increasing blood pressure mostly contributes to blockage of Adenosine A1 and A2 receptors. Since caffeine blocks adenosine A2 receptors which has vasodilatory function, blood vessels become less dilated.(i.e. vasoconstriction) However, it is controversial whether caffeine consumption increases heart rate. Some research shows that caffeine has no influence on heart rate. It is hard to say how much dosage will cause increasing heart rate as no studies have shown significant data. Different people have different tolerance for caffeine based on individual metabolic activity, so there is no clear distinction between caffeine consumption and the amount heart rate increases.Gastrointestinal distress
Caffeine can stimulate the secretion of stress hormones (such as epinephrine and norepinephrine), which can increase blood pressure. Moreover, stress hormones activate the body's "fight or flight" reactions, causing the body to redirect blood supply from the digestive system to muscles. In this way, decreased blood flow to the gastrointestinal tract will slow down the absorption rate and lead to indigestion.Moreover, the additional epinephrine increases the secretion of the main gastric hormone gastrin, which will speed up gastric peristalsis and hypersecretion of gastric juice. Additional gastric acid will lead to acidic chyme going into the small intestine and cause intestinal injury. Therefore, it is not recommended for ulcer patients to drink too much coffee.
Increased urination
Caffeine intake increases renal excretion of sodium and water. This is caused by both slightly increasing the glomerular filteration rate and inhibiting the tubular reabsorption of sodium and water.Although the ability for caffeine and theophylline to induce diuresis and natriuresis is well established, the mechanisms behind them are not well understood.
It has been suggested that inhibition of phosphodiesterases in the proximal tubule may contribute to the diuretic and natriuretic effects of methylxanthines. It has been noted that mice lacking the A1 receptor do not exhibit the diuresis and natriuresis typically elicited by the application of the methylxanthines caffeine or theophylline.
Exercise
Caffeine injections before exercise show no evidence of adverse effects such as dehydration or ion imbalance, and have no effect on short term exercise. However, studies show that 5 mg/kg body weight of caffeine intake allows free fatty acids to mobilize faster, which in turn enhances the endurance performance during long term exercise. This only effects individuals who do not drink caffeine on regular basis. This means that if a 60 kg non-regular caffeine ingesting adult consumes 300 mg of caffeine, which is equivalent to 3 cups of regular coffee, before exercising, he will be able to exercise at the same intensity for a longer period of time. As a side note, the International Olympic CommitteeInternational Olympic Committee
The International Olympic Committee is an international corporation based in Lausanne, Switzerland, created by Pierre de Coubertin on 23 June 1894 with Demetrios Vikelas as its first president...
since the summer of 2000, no longer treats caffeine as a banned substance.
Anxiety
Ingesting single doses of 300 mg of caffeine, which is many times greater than the amount contained in an average caffeine containing beverage, can increase one’s anxiety level. AnxietyAnxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
or panic attacks, caused by ingesting excessive amounts of caffeine is seen more often in consumers with panic disorders. However, panic attacks are most often misdiagnosed with caffeinism, which is virtually indistinguishable from severe chronic anxiety. Caffeinism is a condition caused by ingesting a great amount of caffeine that shows a constellation of symptoms including insomnia, restlessness, excitement, dieresis, and tremors. When examining whether caffeine consumption leads to anxiety and mood changes, it is important to assess the participator’s level of anxiety. It has been claimed that people tend to drink caffeine containing beverages more frequently when they feel nervous, jittery or anxious. In 1986, Shanahan and Huges did a study on whether other stressors are capable of influencing anxiety increased by caffeine intake. Results show that in a healthy individual, consuming 400 mg or more caffeine while performing a stressful task results in increasing anxiety. Generally speaking, increasing levels of anxiousness after caffeine intake are mostly found in consumers who have consumed an amount that would not normally be consumed by majority of consumers. Lower doses of caffeine intake have little effect on consumers’ state. In fact, small amount of caffeine consumption may reduce one’s anxiety level.
Tremors
Higher caffeine consumption leads to tremors and impairs hand steadiness in some individuals.Long-term effects
Research has shown links between heavy caffeine consumption and osteoporosis, high blood pressure, heart disease, heart burn, ulcers, severe insomnia and infertility.Lower risk of type II diabetes
The relationship between caffeine and diabetes mellitusDiabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
has been a controversial topic among scientists.
Caffeine consumption has been associated with a lower risk of diabetes mellitus type 2
Diabetes mellitus type 2
Diabetes mellitus type 2formerly non-insulin-dependent diabetes mellitus or adult-onset diabetesis a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and...
. The majority of the studies on this topic were done on coffee. Test results indicate that consumers who drink at least three or more cups of either caffeinated or decaffeinated coffee every day show a decrease in the risk of type II diabetes. In Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, a recent study was done to examine the relationship between consumption of green, black, and oolong tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...
s and the risk of diabetes; and it was found that caffeine containing beverages were associated with a decreased risk of type II diabetes. The mechanism responsible for this inverse relationship between caffeine containing beverage and the risk of diabetes includes basal energy expenditure, fat oxidation stimulation, glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
mobilization in muscles, and stimulation of increased lipolysis from peripheral tissues. Unfortunately, tolerance of caffeine can develop. Certain antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
substances in these beverages also play roles in decreasing risks of diabetes. For example, epigallocatechin gallate
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
, present in green tea, helps by acting on insulin resistance and glucose metabolism.
Negative effects on diabetics
Although caffeine has been associated with a lowered risk of developing type 2 diabetes, it has also been claimed to have negative effects on diabetes patients, because caffeine is capable of reducing insulin sensitivity and makes it difficult for patients with diabetes to control their blood glucose levels. Studies have shown that caffeine consumption increases blood glucose, but diabetes medication pills decrease blood glucose levels showing that the two counter-interact.Diabetes patients have trouble controlling their sugar level in their blood due to lack of insulin resistance hormone.
Alloxan
Alloxan
Alloxan is an oxygenated pyrimidine derivative. It is present as alloxan hydrate in aqueous solution.-History:...
is a chemical that damages insulin-producing cells and creates conditions for diabetes.
Once in the human body, caffeine produces alloxan and either produces diabetes' conditions or worsens the existing diabetes.
Decrease in Parkinson's disease
Parkinson's diseaseParkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
(PD) is the degeneration of dopamine producing neurons. Dopamine producing neurons stimulate the motor cortex effecting motor control. Loss of dopamine produces loss of motor control skills, cognitive function, and autonomic nervous system.
Epidemiological studies have shown that the risk of developing PD decreases with increasing levels of caffeine intake. Caffeine binds to the adenosine receptor (A2aR) and indirectly prevents MPTP
MPTP
MPTP is a neurotoxin precursor to MPP+, which causes permanent symptoms of Parkinson's disease by destroying dopaminergic neurons in the substantia nigra of the brain...
(an experimental neurotoxin known to cause PD) from destroying dopamine producing neural cells thus preventing neural degeneration and loss of motor control.
Hepatic diseases
Research has shown there is a strong negative correlation to caffeine consumption and liver cirrhosisCirrhosis
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...
. However, there is a lack of evidence for other beverages that contain caffeine. It has been difficult to prove the exact cause for caffeine and its interaction with reducing the risk of liver cirrhosis. In addition, there is other research that shows caffeine to have suppressive effects of Tumor necrosis factor-alpha (TNF-α) induced hepatitis but yet has no effect on Anti-Fas induced hepatitis. Since TNF-α is secreted by macrophages in response of lipopolysaccharide (LPS), and it functions as a apoptoic factors, there are two ways that caffeine could suppress the hepatitis (e.g. by suppressing the TNF-α production and suppress the TNF-α induced apoptosis). However, the specific mechanism is not clear.
Breast and ovarian cancer
Caffeine is suspected to increase the risks in cancerCancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, because it leads to the fluctuation of plasma sex hormones and sex hormone-binding globulin (SHBG) in women. Circulating estrogens and androgens are important factors in female cancer development. Recent studies show that in premenopausal women, there’s an inverse relationship between caffeine intake and total luteal and estradiol levels in the second half of the menstrual cycle, and also has a positive association with progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
levels. Theoretically speaking, lower estrogen levels helps protect against ovarian cancer, but more research needs to be done on this topic.
For postmenopausal women, increased caffeine consumption is associated with a higher level of sex hormone-binding globulin (SHBG), which reduces the estradiol and testosterone activity and decreases the risk of breast cancer.
Digestive cancers
Research has shown that there is no significant association between caffeine consumption and cancers of the mouth, pharynx, esophageal, stomach, liver, or pancreas. In addition, caffeine also decreases the risk of rectalcolon cancers. A possible explanation is that caffeine interferes with bile secretion, reducing bile acid, and thus leaving neutral sterol concentration in the bowel. Another possible explanation is that caffeine may inhibit some chemical carcinogens such as 4-nitroquinoline-1-oxide; however, this is hard to evaluate because other research shows that caffeine can have promotive effects on carcinogenesis.Influences in performance and mood
Caffeine addiction leads to some levels of physical dependence. The most frequently seen withdrawal symptoms are headache and fatigue. Such symptoms affect consumers’ mood, but show no evidence of influencing ones’ performance. In prolonged caffeine drinkers, symptoms such as increased depression and anxiety, nausea, vomiting and intense desire for caffeine containing beverages are also reported. Withdrawal symptoms begin after 12–24 hours and peaks at 20–48 hours after abstinence from caffeine. The symptoms reflect consumers’ expectancy effects on caffeine to some degree.One patient reported: I had symptoms such as the flue, slept day and night for several days. After that, I felt as walking in a fog, far away from life, and had difficulty doing anything. After about three months, the withdrawal symptoms had almost completely declined.
Expectancy effects
Studies with placebo conditions have been done to demonstrate that the effects of caffeine depend greatly on the consumer’s expectations. When heavy caffeine drinkers are led to believe that they are consuming beverages that contain caffeine, they tend to perform better regardless of the caffeine content within the sample that was given to them.Effect of genetics on withdrawal symptoms
Gene polymorphism could be associated with caffeine withdrawal symptoms and beta 1and beta-2 play roles in caffeine withdrawal. For example, compared to people with homozygous Gly16 allele, consumers with the heterozygote ADR beta-2 Gly16 Arg gene polymorphism have a higher chance of feeling fatigue after 48 hours of caffeine withdrawal. It’s been suspected that beta2- adrenoceptors are the main cause to this increase in mental fatigue symptom. Beta 2- adrenoceptors are receptors that regulate glycogenolysis, secret insulin and intramuscularly transport glucose that are used for cerebral and muscle activity. Another example is given by the genes ADRbeta1 Gly16 Arg and CYP1A2-163A>C polymorphisms. They are associated with the consumers’ mood swing and increased depression level. Among subjects homozygous for the CYP1A2 allele, ADRbeta1 Gly389 allele carriers are reported to have a higher percentage of depression level increase when compared to Arg389 homozygotes subjects. Adrenergic receptors, again, play a key role in this symptom, as altered norepinephrine neurotransmission, an adrenoceptor agonist, contribute to the etiology of depression. This symptom is often seen in faster caffeine metabolizers, because caffeine effects diminish quicker in these consumers and provide them less opportunity to adapt to caffeine loss.Adults
Health CanadaHealth Canada
Health Canada is the department of the government of Canada with responsibility for national public health.The current Minister of Health is Leona Aglukkaq, a Conservative Member of Parliament appointed to the position by Prime Minister Stephen Harper.-Branches, regions and agencies:Health Canada...
has not developed definitive advice for adolescents 13 and older because of insufficient data. Nonetheless, Health Canada suggests that daily caffeine intake for this age group be no more than 2.5 mg/kg body weight. This is because the maximum adult caffeine dose may not be appropriate for light weight adolescents or for younger adolescents who are still growing. The daily dose of 2.5 mg/kg body weight would not cause adverse health effects in the majority of adolescent caffeine consumers. This is a conservative suggestion since older and heavier weight adolescents may be able to consume adult doses of caffeine without suffering adverse effects. For the rest of the general population of healthy adults, Health Canada advises a daily intake of no more than 400 mg.
According to the US-based Waverly Health Center, three 8 oz cups of coffee (about 250 milligrams of caffeine) per day is considered an average or moderate amount of caffeine; ten 8 oz cups of coffee per day is considered an excessive intake of caffeine.
Pregnant women
Caffeine's potential impact on female fertility, and its precise impact on pregnancy, is still being studied, but caution and moderation, as with many other substances in these cases, is warranted in any case until further information is known. For women of childbearing age, Health Canada recommends a maximum daily caffeine intake of no more than 300 mg, or a little over two 8 oz (237 mL) cups of coffee.Children
For children age 12 and under, Health Canada recommends a maximum daily caffeine intake of no more than 2.5 milligrams per kilogram of body weight. Based on average body weights of children, this translates to the following age-based intake limits:| Age range | Maximum recommended daily caffeine intake |
|---|---|
| 4-6 | 45 mg |
| 7-9 | 62.5 mg |
| 10-12 | 85 mg |
Relatedly, one study found that caffeine can be used to treat hyperkinetic children. The research showed 200–300 mg of caffeine has a similar effect to methylphenidate
Methylphenidate
Methylphenidate is a psychostimulant drug approved for treatment of attention-deficit hyperactivity disorder, postural orthostatic tachycardia syndrome and narcolepsy. It may also be prescribed for off-label use in treatment-resistant cases of lethargy, depression, neural insult and obesity...
in treating hyperkinetic impulse disorder. Moreover, the caffeine treatment did not show the side-effects caused by methylphenidate.