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Effects of caffeine on health and nutrition: A Review

  • January 2014
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Tsedeke Wolde at WU-JU
Tsedeke Wolde
  • WU-JU
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Abstract

This paper reviews the available literatures and research findings on the effect of caffeine on health and nutrition. Caffeine is a mild stimulant found in many of our favorite beverages and some of our foods, such as coffees, teas, colas, and even chocolate. Caffeine can negatively affect our health if it is not consumed in moderation. Caffeine can cause nutrient depletion of important nutrients, like vitamin B6, and interfere with nutrient absorption of essential minerals, including calcium, iron, magnesium and B vitamins. Studies have found caffeine consumption is associated with reduced risk of developing type 2 diabetes, although the mechanisms are unclear. However, sensitive sub-populations, including pregnant women, children and older individuals, and those with a history of heart disease, may experience effects at lower levels of caffeine and should limit their consumption to three cups of coffee per day, or no more than 300 mg/ day, to avoid adverse effects. Thus, the purpose of this paper is to review the effect of caffeine on health and nutrition. Introduction Caffeine is a naturally occurring chemical stimulant and an alkaloid belonging to a class of compounds called methylxanthines. Its chemical formula is C8-H10-N4-O2. Caffeine is one of the most comprehensively studied ingredients in the food supply. Yet, despite our considerable knowledge of caffeine and centuries of safe consumption in foods and beverages, questions and misperceptions about the potential health effects associated with caffeine persist (IFIC, 2003). Caffeine can act as antioxidant to prevent diseases. Antioxidants are substances that help protect cells in the body against damage acting as a defense against oxidative damage. The role of an antioxidant is to help reduce oxidation reactions and thus reduce damage to body tissues. Antioxidants have been linked to a number of potential health benefits, including protection against heart disease and most forms of cancer. Chlorogenic acid, caffeic acid, and melanoidins are all the types of antioxidants found in coffee. Coffee is one of a number of drinks that contain high antioxidant content. Antioxidants are also found in tea, cocoa and red wine. But there are four times more antioxidants in coffee than in tea (Escott-Stump, 2008). Caffeine rapidly absorbed following oral consumption peak blood (plasma) levels usually within 30 minutes. Then distributes into all body compartments – pass easily into brain, breast milk and crosses placenta. Then metabolized in the liver changed to di and mono-methylxanthines and finally filtered by the kidneys and they exit the body with the urine. How long it takes to leave caffeine from the body? it varies between individuals for example, an average adult – 3-5 hrs, child less than 6 months – 24 hrs, Pregnant – 7-8 hrs, and Smoker – 2-3 hrs (IFIC, 2003). At present, there is little evidence to show consumption of caffeine increases the risk of cancer. Studies have shown no negative association, and possibly some protective effects, between caffeine consumption and several types of cancer (IFIC, 2003). Caffeine consumption may help reduce the risk of several chronic diseases, including diabetes, liver disease, and cancer, as well as improve immune function but it has also risk for developing coronary artery disease, osteoporosis, gastritis, iron deficiency anemia, and still births (IFIC, 2003). Caffeine can cause nutrient depletion of important nutrients, like vitamin B6, and interfere with nutrient absorption of essential minerals, including calcium, iron, magnesium, and B vitamins (Escott-Stump, 2008).
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Effects of caffeine on health and nutrition: A Review
Tsedeke Wolde
Lecturer of Nutrition, Department of Public Health, College of Medical and Health Sciences, Wollega
University, Nekemte, Ethiopia
Abstract
This paper reviews the available literatures and research findings on the effect of caffeine on health and
nutrition. Caffeine is a mild stimulant found in many of our favorite beverages and some of our foods, such as
coffees, teas, colas, and even chocolate. Caffeine can negatively affect our health if it is not consumed in
moderation. Caffeine can cause nutrient depletion of important nutrients, like vitamin B6, and interfere with
nutrient absorption of essential minerals, including calcium, iron, magnesium and B vitamins. Studies have
found caffeine consumption is associated with reduced risk of developing type 2 diabetes, although the
mechanisms are unclear. However, sensitive sub-populations, including pregnant women, children and older
individuals, and those with a history of heart disease, may experience effects at lower levels of caffeine and
should limit their consumption to three cups of coffee per day, or no more than 300 mg/ day, to avoid adverse
effects. Thus, the purpose of this paper is to review the effect of caffeine on health and nutrition.
Key words: caffeine, health, diseases and nutrition.
Introduction
Caffeine is a naturally occurring chemical stimulant and an alkaloid belonging to a class of compounds called
methylxanthines. Its chemical formula is C8-H10-N4-O2. Caffeine is one of the most comprehensively studied
ingredients in the food supply. Yet, despite our considerable knowledge of caffeine and centuries of safe
consumption in foods and beverages, questions and misperceptions about the potential health effects associated
with caffeine persist (IFIC, 2003).
Caffeine can act as antioxidant to prevent diseases. Antioxidants are substances that help protect cells in the
body against damage acting as a defense against oxidative damage. The role of an antioxidant is to help reduce
oxidation reactions and thus reduce damage to body tissues. Antioxidants have been linked to a number of
potential health benefits, including protection against heart disease and most forms of cancer. Chlorogenic acid,
caffeic acid, and melanoidins are all the types of antioxidants found in coffee. Coffee is one of a number of
drinks that contain high antioxidant content. Antioxidants are also found in tea, cocoa and red wine. But there are
four times more antioxidants in coffee than in tea (Escott-Stump, 2008).
Caffeine rapidly absorbed following oral consumption peak blood (plasma) levels usually within 30 minutes.
Then distributes into all body compartments – pass easily into brain, breast milk and crosses placenta. Then
metabolized in the liver changed to di and mono- methylxanthines and finally filtered by the kidneys and they
exit the body with the urine. How long it takes to leave caffeine from the body? it varies between individuals for
example, an average adult – 3-5 hrs, child less than 6 months – 24 hrs, Pregnant – 7-8 hrs, and Smoker – 2-3 hrs
(IFIC, 2003).
At present, there is little evidence to show consumption of caffeine increases the risk of cancer. Studies have
shown no negative association, and possibly some protective effects, between caffeine consumption and several
types of cancer (IFIC, 2003).
Caffeine consumption may help reduce the risk of several chronic diseases, including diabetes, liver disease, and
cancer, as well as improve immune function but it has also risk for developing coronary artery disease,
osteoporosis, gastritis, iron deficiency anemia, and still births (IFIC, 2003). Caffeine can cause nutrient depletion
of important nutrients, like vitamin B6, and interfere with nutrient absorption of essential minerals, including
calcium, iron, magnesium, and B vitamins (Escott-Stump, 2008).
Most studies have found that caffeine consumption does not reduce bone mineral density in women who
consume adequate calcium. However, positive associations between caffeine consumption and hip fracture risk
in three studies imply that limiting coffee consumption to three cups per day (about 300 mg/day of caffeine) may
help prevent osteoporosis- related fractures in older adults (IFIC, 2003).
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Although epidemiological data on the effects of caffeine during pregnancy are conflicting, the evidence suggests
that women who are pregnant or are planning to become pregnant, or who are breastfeeding, can safely consume
caffeine, but should limit their consumption to three cups of coffee per day, providing no more than 300 mg/day
of caffeine (IFIC, 2003).
Sources of caffeine
Caffeine is a naturally occurring substance found in the leaves, seeds and/or fruits of at least 63 plant species
worldwide and is part of a group of compounds known as methylxanthines. The most commonly known sources
of caffeine are coffee, cocoa beans, kola nuts and tea leaves [Frary et al., 2005].
The amount of caffeine in food products varies depending upon the serving size, the type of product, and
preparation method. With teas and coffees, the plant variety also affects the caffeine content. An eight-ounce cup
of drip-brewed coffee typically has 65-120 mg caffeine; an eight-ounce serving of brewed tea has 20-90 mg; and
a 12- ounce canned soft drink has 30-60 mg [Knight, et al., 2004]. Energy drinks can contain 50- 160 mg or
more per eight-ounce serving, plus caffeine from guarana and other added sources not normally declared as
caffeine; and one ounce of solid milk chocolate typically has just six mg caffeine[ABA, 2007; Mayo Clinic,
2005].
Other sources of caffeine include over-the-counter pain relievers. Caffeine is an adjuvant—it increases the rate at
which the medication is absorbed into the body. It is also present in some stimulant tablets and cold medications.
Caffeine can be present in these products ranging from 16-200 mg [Cleveland Clinic, 2006].
Caffeine daily consumption intake
The per capita consumption level of caffeine for all consumers (of all ages) is approximately 120 mg per day, or
a mean intake of 1.73 mg/kg body weight/ day [Knight et al., 2004].
Children consume significantly less caffeine than adults. As of 2004, the average daily intake of caffeine by
young children ages 1-5 and 6-9 years from all caffeinated beverages was 14 and 22 mg/day, or 0.82 and 0.85
mg/kg body weight/day, respectively [Knight et al., 2004]. For children and young adults, the primary sources
of caffeine are soft drinks and teas, while for adults ages 25 and older; it is mostly derived from coffee [Knight et
al., 2004].
However, a growing beverage category, energy drinks, is a popular choice with several age groups, and is a
category to monitor for consumption in the coming years.
Evidence from both scientific reviews and specific studies on consumption of caffeine generally concludes that
daily consumption of 300 mg/day, or about three cups of coffee, is safe, even for more sensitive segments of the
population, such as young children and pregnant women [Nawrot et al., 2003].
Functions of caffeine
Caffeine is absorbed and passes quickly into the brain. It does not collect in the blood stream or get stored in the
body. It leaves the body in the urine many hours after it has been consumed. There is no nutritional need for
caffeine. It can be avoided in the diet. Caffeine stimulates, or excites, the brain and nervous system. It will not
reduce the effects of alcohol, although many people still believe a cup of coffee will help a person "sober-up."
Caffeine may be used for the short-term relief of fatigue or drowsiness (Escott-Stump, 2008).
Side effects of caffeine
Anxiety
Depression
Difficulty sleeping
Nausea
Restlessness
Tremors
A fast heart rate
Urinating more often
VomitingStopping caffeine abruptly may cause withdrawal symptoms, such as:-
Drowsiness
Headaches
Irritability
Nausea, and
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Vomiting
• Reduce caffeine gradually to prevent any symptoms of withdrawal.
• The effect of caffeine on health has been widely studied.
• Large amounts of caffeine may decrease bone mass density, most likely by interfering with the body's
ability to absorb calcium. This may lead to osteoporosis.
• Caffeine may cause or worsen painful, lumpy breasts (fibrocystic disease).
• Caffeine may have a negative effect on a child's nutrition if caffeinated drinks replace healthy drinks,
such as milk. A child who consumes caffeine may also eat less, because caffeine reduces the appetite (Escott-
Stump, 2008).
Effect of caffeine on health and diseases
Cardiovascular health
The relationship between coffee, caffeine and cardiovascular health markers has been explored, with emphasis
on cardiac arrhythmia, heart rate, serum cholesterol and blood pressure. In his review, Nawrot et al. (2003)
concluded that moderate caffeine consumption (400 mg or less, or four or fewer cups of coffee per day) does not
adversely affect cardiovascular health. Insufficient data exist to be able to draw conclusions about the risk of
coronary heart disease (CHD) or mortality associated with consumption of much higher amounts.
Hypertension (high blood pressure) is a recognized risk factor for CHD and stroke. Caffeine can acutely raise
heart rate and blood pressure immediately after consumption, although regular caffeine consumers can build up a
tolerance to these effects. Although the impact of coffee on blood pressure was first debated nearly thirty years
ago, extensive epidemiological studies have confirmed that there is no link between coffee consumption and
hypertension, hyperlipidemia, and coronary artery disease (CAD) (Nawrot et al., 2003). One study has linked
caffeine intake to abnormal heart rhythms, particularly premature atrial and ventricular contractions of the heart.
In this study, caffeine taken in tablet form resulted in blood pressure elevations four times greater than for
caffeinated coffee. Thus, although there appears to be no clear evidence for a strong causal relationship between
caffeinated coffee and abnormal heart rhythms, it is not as clear when considering caffeine alone or in beverages
other than coffee [Frishman and Sonnenblick, 2002].
Although scientific review author James (2004) suggested there is strong experimental evidence that blood
pressure remains reactive to caffeine in the diet, and that overall epidemiological evidence implicates caffeine as
a risk factor for hypertension, more recent studies on women have not supported this. According to the American
Heart Association (AHA)’s policy on caffeine, “Whether high caffeine intake increases the risk of coronary heart
disease is still under study” [AHA, 2007].
In the study by Lopez-Garcia et al. (2006), researchers found that coffee consumption was not associated with an
increased risk of CHD. In the Nurses’ Health Studies I and II, coffee consumption, even at high levels, appeared
to have no effect on blood pressure; however, both regular and diet colas caused a modest increase in blood
pressure. This apparent contradiction was thought to be due either to an ingredient other than caffeine or by a
protective effect of another component of coffee. People already suffering from high blood pressure should
consult a physician about their caffeine intake, as they may be more sensitive to the effects of caffeine on blood
pressure [Winkelmeyer et al., 2005].
Reproductive health
There are several comprehensive review papers that examine the relationship between caffeine and reproductive
health. A review by Leviton and Cowan [2002] specifically examined outcomes such as delayed conception,
miscarriage (both chromosomally normal and aberrant), birth defects, premature birth, and low birth weight and
found that caffeine does not cause any of these outcomes. The authors concluded that the associations found in
the less rigorously analyzed studies could possibly be due to other factors, such as smoking.
Christian and Brent (2001) conducted a very systematic review on the relationship between caffeine
consumption by both pregnant women and women of child-bearing age and the occurrence of congenital
malformations, fetal growth retardation, small-for-date babies, miscarriages, behavioral effects, maternal
infertility and genetic effects.
The only statistically significant results were teratogenic (birth defect) effects in rats administered extremely
high levels of caffeine intravenously, which do not necessarily translate to humans and also could never be
attained merely by drinking beverages containing caffeine.
Fertility
Nawrot et al. (2003) noted in their review of caffeine that most epidemiological studies on caffeine and fertility
were affected by methodological issues, including inadequate measurement of caffeine intake, inadequate
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control for possible confounding factors, recall bias in retrospective studies, lack of data on frequency of
unprotected intercourse and, in some studies, inadequate sample size. Despite these limitations, the
epidemiological studies generally indicate that consumption of caffeine at levels at or below 300 mg per day, or
approximately three cups of coffee per day, did not reduce fertility in otherwise fertile women.
A study on the effects of alcohol and caffeine on fertility demonstrated a significant risk when alcohol and
caffeine were consumed together; however no effects were observed when caffeine was consumed alone
[Nawrot et al., 2003].
Miscarriage
There have been numerous epidemiological studies examining the relationship between coffee or caffeine intake
by pregnant women and the risk of miscarriage. Some studies have observed significant associations between
caffeine intakes greater than 300 mg/day, particularly from coffee, and the risk of miscarriage, whereas other
studies have not [Higdon and Frei, 2006]. While individual epidemiological studies cannot prove cause and
effect, they can contribute to the wealth of information on potential observed effects. However, they must be
taken within the context of the entire body of data [Nawrot et al., 2003].
Birth defects (teratology)
The majority of epidemiological studies have found that maternal caffeine consumption is not associated with
increased risk of congenital malformations, or birth defects, in fetuses [Higdon and Frei, 2006]. At present, there
is no convincing evidence from epidemiological studies that moderate caffeine consumption by pregnant women
ranging from 300–1,000 mg per day throughout the entire pregnancy increases the risk of birth defects [Nawrot
et al., 2003]. However, in light of other women’s health issues, such as fertility and miscarriage, pregnant
women are advised to keep caffeine consumption at or below 300 mg/day (or approximately three cups of
coffee).
Bone health (osteoporosis)
Given the increased awareness of the incidence of osteoporosis in post-menopausal women, research on the
relationship between caffeine intake and bone health has been a particular area of focus. Consumption of large
amounts of caffeine (more than 744 mg/day) has been shown to increase urinary excretion of calcium and
magnesium [Tucker, 2003]. However, calcium excretion is complex and is affected by many other dietary
constituents such as calcium, potassium, phosphorus, isoflavones, antioxidants, salt, oxalate, phytates, and
protein [Massey, 2003; Atkinson and Ward, 2001]. Studies on caffeine and calcium metabolism and bone
deterioration show that, as caffeinated coffee consumption increases, milk consumption decreases. Bone
deterioration becomes more pronounced when dietary calcium is inadequate, and less pronounced when dietary
calcium intake is adequate.
Nawrot et al. (2003) concluded that caffeine’s potential to adversely affect calcium balance and bone metabolism
is dependent on lifetime caffeine and calcium intakes, and is critical for women. Based on the data reviewed, the
authors suggested that caffeine intake of less than 400 mg/day does not have significant effects on bone density,
nor on calcium balance in individuals consuming at least 800 mg calcium per day. Higdon and Frei (2006) also
suggested that, although most studies have not found coffee or caffeine consumption to reduce bone mineral
density in women who consume adequate calcium, positive associations between caffeine consumption and hip
fracture risk in three prospective cohort studies suggest that limiting coffee consumption to three cups of coffee
per day (about 300 mg of caffeine per day) may help prevent hip-bone fractures in older adults.
Cancer
Most of the research on possible links between cancer and caffeine has been conducted on coffee and tea.
Therefore, it is extremely difficult to isolate the effects of caffeine unless the research specifically focuses on
caffeine. Consequently, research on caffeine and its effects on cancer, if any, is sparse. There are however,
references in coffee and tea research relating to caffeine that are generally positive.
Nawrot et al. (2003) concluded in his review of the research that caffeine is unlikely to be a human carcinogen at
levels below five cups of coffee per day (or less than 500 mg caffeine per day). Furthermore, the overall
evidence indicates that caffeine, as present in coffee, does not cause breast or bowel cancer. Moreover, although
early case control studies appeared to link caffeine intake to pancreatic, bladder and ovarian cancers, more
recent, better designed studies have not supported these conclusions [Tavani and La Vecchia, 2004; Zeegers et
al., 2004]. A number of case control studies have demonstrated reduced risk of colorectal cancer with coffee
consumption [Tavani and La Vecchia, 2004; Higdon and Frei, 2006]. In a review, Tavani and La Vecchia (2004)
showed that not only was there no risk of colon or colorectal cancer with caffeinated beverages, but there may
even be a protective effect. A study by Michels et al. (2005) confirmed that there is no association between rectal
cancer and consumption of caffeinated beverages.
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Reduced risk of diabetes
In both cohorts, higher caffeine intakes were associated with significant reductions in diabetes risk. In contrast,
tea consumption did not affect type 2 diabetes risks in either study [Salazar-Martinez, et al., 2004]. Van Dam and
Hu [2005] conducted a systematic review of nine cohort studies, including more than 193,000 men and women,
and found a 35% lower risk of type 2 diabetes in those who consumed at least six cups of coffee per day, and a
28% lower risk in those who consumed between four and six cups per day, compared to those who consumed
less than two cups per day. In another long-term study of the relationship between caffeinated beverage
consumption and incidence of type 2 diabetes, the authors followed more than 41,000 participants over ten years,
assessing coffee consumption every two to four years. The results suggest that caffeine intake from coffee and
other source is associated with a significantly lower risk for type 2 diabetes [Salazar-Martinez, et al., 2004].
Recovery from liver injury
The study conducted a prospective study to examine the relationship between coffee and tea consumption and
incidence of chronic liver disease [Ruhl and Everhart, 2005a]. The results showed that individuals who consume
more than two cups of coffee or tea per day have less than half the risk of developing chronic liver disease as
those who drink less than one cup of coffee per day.
Effect of caffeine on nutrition
The effect of caffeine on vitamin and minerals absorption
Caffeine is a mild stimulant found in many of our favorite beverages and some of our foods, such as coffees,
teas, colas, and even chocolate. Because caffeine can negatively affect our absorption of nutrients, it's important
to pay attention to the amount we consume. Moderate caffeine intake (300 mg or less per day) is probably not
harmful to most healthy adults; however, regular large amounts (over 350 mg per day) may cause dependency,
nutrient depletion, and interference with nutrient absorption. Many also take a multivitamin supplement daily as
a part of their morning routine. Not many people are aware that taking vitamins at the same time as a cup of
coffee or tea can interfere with the body’s absorption of many necessary nutrients (Escott-Stump, 2008).
Calcium
Caffeine causes calcium to be excreted in the urine and feces. For every 150 mg of caffeine ingested, about the
amount in one cup of coffee, 5 mg of calcium is lost. This effect occurs even hours after the consumption of
caffeine. One study of postmenopausal women found that those who consumed more than 300 mg of caffeine
lost more bone in the spine than women who consumed less.
Caffeine also inhibits the amount of calcium that is absorbed through the intestinal tract and depletes the amount
retained by the bones. Studies have shown that women with high caffeine intake suffer more hip fractures than
those who avoid caffeine or drink in moderation (1 to 2 cups per day) (Escott-Stump, 2008).
Vitamin D
Caffeine inhibits vitamin D receptors, which limit the amount that will be absorbed. Because vitamin D is
important in the absorption and use of calcium in building bone, this could also decrease bone mineral density,
resulting in an increased risk for osteoporosis (Escott-Stump, 2008).
Iron
Caffeine interferes with the body’s absorption of iron, which is necessary for red blood cell production. Drinking
caffeine at the same time as an iron source can reduce absorption by up to 80%, according to the Nutrition Desk
Reference. Any beverage containing caffeine should be separated from iron-containing foods or supplements by
at least one hour (Escott-Stump, 2008).
B Vitamins
Caffeine has a mild diuretic effect, which increases urination. Water soluble vitamins, such as the B-vitamins,
can be depleted as a result of the fluid loss. In addition, it interferes with the metabolism of some B-vitamins,
such as thiamine (vitamin B1). The one exception to this rule appears to be vitamin B12. Caffeine stimulates the
production of stomach acid, which actually helps the body absorb B12 (Escott-Stump, 2008).
Other Vitamins and Minerals
Caffeine may reduce the absorption of manganese, zinc and copper. It also increases the excretion of the
minerals magnesium, potassium, sodium and phosphate. There is also evidence that caffeine interferes with the
action of vitamin A (Escott-Stump, 2008).
Conclusion
As clearly discussed in the above review, there is evident that caffeine consumption at varying levels may help
reduce the risk of several chronic diseases. Sensitive sub-populations, including pregnant women, children and
older individuals, and those with a history of heart disease, may experience effects at lower levels of caffeine and
should limit their consumption to three cups of coffee per day, or no more than 300 mg/ day, to avoid adverse
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effects. Caffeine can cause nutrient deficiencies that can affect both health and quality of life. As with most
dietary factors, moderation and balance are keys in optimal nutrition intake.
Acknowledgment
The author would like to thanks Wollega University for the facilities available for literature search and technical
support.
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... [20] When caffeine reaches its target organs, its biological action occurs through several mechanisms including the adenosine receptor antagonism. [21] Also, caffeine interacts with other receptors, such us vitamin D receptors [22] and the epidermal growth factor receptor (EGFR). [23] In addition, caffeine elevates intracellular cyclic adenosine monophosphate concentration (cAMP). ...
... Many studies have also proven that in adults, elevated and chronic consumption of caffeine can cause many health problems like hypercalciuria , osteoporosis, hip fracture, nervousness, increased diuresis, insomnia and gastrointestinal disturbances. [22] Besides, numerous in vivo and in vitro studies have reported excessive caffeine consumption to be detrimental to the musculoskeletal-system, comprising the hyaline cartilage. [26] High content of phosphoric acid in soft drinks has been suggested as one of the linking mechanisms between these drinks and exposure to fracture. ...
Harmful effects of chronic consumption of soft drinks on the bone metabolism of laboratory female rats
Article
Full-text available
  • Dec 2022
Consumption of soft drinks can result in depletion and deficiency of calcium, and thus increase the risk of osteoporosis and exposure to fracture. The present study was performed to inspect the consequences of long term usage of soft drink on metabolism and histopathology of bone. Twenty-four female albino white rats (Rattus norvigicus) were randomly divided into six groups each containing four animals: two control groups (1 & 2) were fed with regular pellet; two coca-cola groups (3 & 4) were fed with standard pellet diet and given coca cola (2 ml) once a day and two Seven up (7up) groups (5 & 6) were fed with standard pellet diet and given 7up (2 ml) once a day. The treatment continued for two different timelines i.e. groups 1, 3 and 5 were treated for two weeks, while groups 2, 4 and 6 were treated for four months. Cardiac puncture technique was used for taken blood samples for measurement of calcium, inorganic phosphate, magnesium, Vitamin D3 and bone forming biomarkers including alkaline phosphate and osteocalcin. In addition, level of bone resorption biomarker bone sialoprotein in serum was also measured. Calcium and inorganic phosphate, alkaline phosphate, osteocalcin and bone sialoprotein considerably elevated (p≤0.05) in rats which were given soft drinks daily for 4 months. Magnesium and Vitamin D3 significantly decreased (p≤0.05) in rats treated with coca cola for 4 months compared with the control and the other groups. Histopathological study revealed changes in the bone of groups fed with coca cola and 7up for 4 months. It showed many empty lacunae, osteocytes inside indistinct lacunae and numerous resorption cavities of inconstant size in the trabecular plates. In conclusion, chronic consumption of soft drinks has harmful effects on bone health and a significant rise in the concentrations of bone remodeling markers demonstrated a rise in bone-turnover-rate and increased risk of osteoporosis. Abstract INTRODUCTION
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... Caffeine is an alkaloid belonging to methylxanthine. It is also a chemical stimulant found naturally (Wolde 2014). Studies showed that coffee consumption has chronic and acute effects on human health (Nędzarek et al. 2013). ...
... Caffeine also can reduce the risk of several chronic diseases such as liver cancer, diabetes, coronary heart disease, osteoporosis, and gastritis (Nartea et al. 2022). Moreover, the absorption of many vital nutrients such as vitamin B 6 is reduced by caffeine intake and the absorption of essential minerals such as magnesium (Mg), iron (Fe), and calcium (Ca) (de Mejia and Ramirez-Mares 2014;Escott-Stump 2008;Wolde 2014). However, consuming large amounts of this drink is not recommended because of some contaminants, including mycotoxins and potentially toxic elements (PTEs), besides to adverse effects of caffeine (Barrea et al. 2021;Batrinou et al. 2020;Berman et al. 2022;Khaneghah et al. 2019;Nourbakhsh and Tajbakhsh 2021;Pavithra 2021;Yazdanpanah et al. 2022). ...
The concentration of potentially toxic elements (PTEs) in the coffee products: a systematic review and meta-analysis
Article
Full-text available
Coffee is one of the most consumed products globally, and its contamination with potentially toxic elements (PTEs) occurs throughout the production chain and production. Therefore, the current meta-analysis study aimed to estimate the concentration of essential elements (Cu and Co) and the contamination of PTEs (Ni, Cr, Pb, As, and Cd) in coffee. The recommended databases, including PubMed, Scopus, and ScienceDirect, were investigated to collect data regarding the contamination of PTEs in coffee products from 2010 to 2021. Among 644 retrieved citations in the identification step, 34 articles were included in the meta-analysis. The pooled mean concentration of essential elements in coffee products is much higher than that of toxic elements (Co (447.106 µg/kg, 95% CI: 445.695–448.518 µg/kg) > Ni (324.175 µg/kg, 95% CI: 322.072–326.278 µg/kg) > Cu (136.171 µg/kg, 95% CI: 134.840–137.503 µg/kg) > Cr (106.865 µg/kg, 95% CI: 105.309–108.421 µg/kg) > Pb (21.027 µg/kg, 95% CI: 20.824–21.231 µg/kg) > As (3.158 µg/kg, 95% CI: 3.097–3.219 µg/kg) > Cd (0.308 µg/kg; 95% CI: 0.284–0.332 µg/kg)). Results showed high differences between pooled concentrations of all PTEs in coffee products of different countries.
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... However, the importance of caffeine as a pharmaceutical compound goes beyond just being a stimulant drug (Monteiro et al., 2019), where its effectiveness as a drug was studied for many medical cases to reduce their intensity or their possibility of accruing, such as consuming coffee may stimulate the gallbladder, which will reduce the risk of gallstones (Grosso et al., 2017). Caffeine could also reduce the development of some diseases like Parkinson's risks by protecting the brain cells (Aaseth et al., 2018), and it can relieve asthma attacks (Wolde, T. 2014, Platritis et al., 2013. Although caffeine has health benefits, some adverse health effects may come along with high consumption rates, such as high incorporation with decreasing bone density, which leads to osteoporosis (Bijelic et al., 2017 (Ali, 2019). ...
Assessment of Ultrasound-Assisted Extraction of Caffeine and its Bioactivity
Article
Full-text available
  • Mar 2023
This research focuses on using spent coffee grounds as a source of caffeine by ultrasound-assisted extraction technique. Two types of ultrasound techniques (ultrasonic bath and ultrasonic probe) were studied to extract caffeine. The effect of the sonication type sonication power, extraction time, and extraction temperature on the extraction efficiency was investigated. The results demonstrated that extraction by an ultrasonic probe is superior to ultrasonic bath extraction. The highest caffeine recovery was obtained at 55OC by using an ultrasound bath where caffeine concentration was 795.74mg /L after 60 min. The bioactivity of extracted caffeine was also studied and compared with the bioactive of standard caffeine against candida albicance yeast. The results showed that the minimum inhibition concentration for natural caffeine was 100 mg/L which is half of the minimum inhibition concentration of standard caffeine.
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... It was later found in mate and various other plants, eventually it was found that theine of tea was identical with the Caffeine of coffee and the term Theine then was dropped [4] . Caffeine is known as 1, 3, 7-trimethyl xanthine or 3, 7 dihydro-1, 3, 7-trimethyl-1-H purine-2, 6-dione [5] . The actual source of caffeine is coffee beans, kola nuts, cocao pods and dried leaves of Camellia sinensis. ...
Qualitative and quantitative analysis of caffeine in some commercial brands of tea consumed in India
Article
  • Dec 2017
Caffeine is a common organic molecule found in many beverages such as coffee, tea, energy drinks and cola, which make the drinks addictive. Caffeine has drawn more attention due to its physiological effects beyond its stimulatory effect on central nervous system, hence it is used both recreationally and medically to reduce physical fatigue and restore mental alertness when unusual weakness or drowsiness occurs. Caffeine content in various energy drinks and beverage varies from 10 to 50 mg of caffeine per serving; however the US Food and Drug Administration (FDA, 2006) limits the maximum amount in carbonated beverages to 6 mg/oz. Large amount of caffeine consumption can cause physiological and psychiatrically dependence. The aim of this study is to determine the concentration of caffeine in tea brands available in India to ensure whether the caffeine concentration in the follow tea as per FDA recommendation or not. There are few reputed brands like Taj, Red Label, Agni and other local brands like Mohini, and Krishna Gopal were studied, by using simple and fast standard UV-Visible spectrophotometric method. The minimum caffeine level was observed in the Mohini brand tea, while Taj tea brand sample showed the highest caffeine content.
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... In addition, some evidence suggests that caffeine consumption is associated with inhibition of intestinal calcium absorption and increased urinary excretion of calcium and magnesium [7]. Caffeine consumption may also affect other biochemical markers, such as albumin, alkaline phosphatase (ALP), phosphate, and ferritin. ...
Total 25(OH)D Concentration Moderates the Association between Caffeine Consumption and the Alkaline Phosphatase Level in Pregnant Women
Article
Full-text available
  • Apr 2022
The evidence as to whether caffeine consumption is beneficial or harmful to human health has been mixed. This study aimed to examine the effect of 25-hydroxyvitamin D (25(OH)D) concentration on the association between caffeine consumption and mineral metabolism in pregnant women. This is a cross-sectional study involving pregnant women at their 25th to 35th gestational week recruited at antenatal clinics in the period of July 2019 to December 2020. Peripheral blood samples were collected to determine their total 25(OH)D, albumin, alkaline phosphatase (ALP), calcium, phosphate, and ferritin level in serum. Questionnaires on demographics and dietary intake were also administered. Among 181 pregnant women recruited (Average age = 32.9 years), 50 (27.6%) of them were found to be vitamin D insufficient (25(OH)D concentration < 75 nmol/L), and 131 (72.4%) were vitamin D sufficient (25(OH)D concentration ≥ 75 nmol/L). Adjusted regression models identified an association between higher caffeine intake and lower ALP level only among vitamin D-sufficient pregnant women (β = −0.24, p = 0.006), but not in those with insufficient vitamin D (β = −0.02, p = 0.912). The findings provide new insights into 25(OH)D concentration as a potential modifier of the health effects of caffeine consumption during pregnancy.
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... The most common food preferences comprise caffeine, alcohol, fruits, and vegetables containing vitamins and fats. Caffeine is a nutrient that can be found in many beverages and plays an important role in health because of its interference in Vitamin B and essential mineral absorption [2]; moreover, in low doses, besides producing an increase in mental energy and attention, and elevated mood, it also has antioxidant properties [3]. Vitamins, and especially Vitamins A and D, have a crucial effect on the regulation of immune responses and have a protective role in inflammation and autoimmunity. ...
The Potential Impact of Blood System on Dietary Habits and Smoking
Article
Full-text available
  • Jan 2022
The ‘Blood-Type’ diet advises individuals to eat according to their ABO blood group to improve their health and decrease the risk of chronic diseases. However, the food preferences of individuals with different blood groups have not been examined. The aim of our study was to investigate, in healthy regular blood donors (rBDs), the associations of smoke, alcohol, caffeine, vitamin and fat intake with their different blood groups and if ABO groups could be a potential predictor tool for disease prevention. A total of 329 volunteers were divided into four groups according to their ABO types: Group 1 (A) comprised 141 rBDs; Group 2 (B), 65 rBDs; Group 3 (O), 96 rBDs; and Group 4, 27 rBDs. Additionally, they were divided into two groups according to their rhesus types and their preferences for smoke, too. Dietary intake was assessed using 3-day food recall and the Food Processor computer program for nutrient analysis. Alcohol, caffeine, sugar and Vitamin D consumption were significantly (p < 0.05) higher in the O group. The A group presented statistically significantly (p < 0.05) greater preferences for cholesterol intake and a higher trend for smoking (25%) habits compared with all the other groups, whereas Group B preferred more fatty foods. The blood group AB appeared to be the most controlled food intake group. Regarding the rhesus comparisons, alcohol; caffeine; and Vitamin C, D, E and K consumptions were significantly (p < 0.05) higher in rhesus-positive individuals than their rhesus-negative counterparts. For the non-smoker group, compared with the smokers, a higher consumption of Vitamin D and fibers was found. In conclusion, in the present study, statistically significant correlations of the ABO and rhesus system with some dietary parameters were found, indicating a consequent influence of these preferences on the progression of different diseases.
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... Its high prevalence of intake in the worldwide diet has arisen significant scientific interest in its effects on human health. Caffeine consumption has been studied as a risk factor for many diseases and conditions, including hypertension, cardiovascular diseases, bone density, various cancers, mental and behavioral disorders, and reproduction and developmental abnormalities [8][9][10] . However, studies to evaluate the effect of caffeine on hearing loss are contradictory. ...
Urine caffeine metabolites and hearing threshold shifts in US adults: a cross-sectional study
Article
Full-text available
  • Nov 2021
Previous studies have reported the relationship between effect of caffeine and many diseases. However, studies to evaluate the association between caffeine and hearing loss are contradictory. To examine the relationship of urinary caffeine metabolites with the hearing threshold in US adults, a total of 849 adults aged 20–69 years who participated in the National Health and Nutrition Examination Survey (NHANES, 2011–2012) were enrolled in this study. Urinary caffeine and its 14 metabolites were applied as biomarkers to assess caffeine exposure. Hearing loss was defined as mean pure tone averages > 25 dB HL at 500, 1000, and 2000 Hz in both ears (low frequency); and 3000, 4000, and 6000 Hz in both ears (high frequency). Univariate and multivariate linear regression analyses were conducted to examine the associations of urinary caffeine metabolites with low- and high-frequency hearing thresholds, respectively. Low-frequency hearing loss were 5.08% and 6.10% in male and female participants, respectively; and high-frequency hearing loss were 31.81% and 15.14% in male and female participants, respectively. In the unadjusted model, the P value for trend shows that urinary caffeine metabolites 137X and AAMU were significantly associated with low-frequency PTA, and that 17X, 137X, AAMU were significantly associated with high-frequency PTA, but when the model was adjusted for sex, age, education level, firearm noise exposure, occupational noise exposure, recreational noise exposure, serum cotinine, body mass index, diabetes, hypertension, these were no longer statistically significant. In conclusion, urinary caffeine metabolites were not associated with the hearing threshold shifts in US adults.
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The effect of coffee on contralateral suppression of transient evoked otoacoustic emissions
Article
  • Sep 2023
Background : Coffee is a popular non-alcoholic beverage consumed by humans across the world. It contains caffeine, which is a type of stimulant of the central nervous system. In the auditory system, it has a positive effect on auditory brainstem response and perception of speech in noise. Further, caffeine has an inhibitory effect in the cochlea, but studies have rarely investigated its effect on otoacoustic emissions (OAEs) in humans. OAEs are low-intensity sounds produced by the cochlea, which could be recorded in the ear canal. The present study was carried out to investigate the effect of coffee on transient evoked otoacoustic emission (TEOAE) and contralateral suppression of TEOAE. Method : A total of 52 young adults participated in the study. A cross-over study design was used for the present investigation. The TEOAE and contralateral suppression of TEOAE were recorded before and after consumption of coffee and milk. The contralateral suppression of TEOAE was measured by presenting white noise to the contralateral ear at 40, 50, and 60 dB sound pressure level (SPL). Results : The mean amplitude of TEOAE before and after consumption of coffee was similar in both ears. Further, the mean contralateral suppression of TEOAE was slightly larger after consumption of coffee in both ears. However, the mean difference was not significant in both the ears. Conclusions : Based on the findings of present study, coffee has no significant effect on the amplitude of TEOAE and contralateral suppression of TEOAE.
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The influence of physiological and lifestyle factors on essential mineral element isotopic compositions in the human body: implications for the design of isotope metallomics research
Article
In the last 20 years, the application of high-precision isotopic analysis of essential mineral elements (Mg, K, Ca, Fe, Cu and Zn) to biomedicine (sometimes referred to as isotope metallomics), has revealed that their stable isotopic compositions are altered by the metal dysregulation that is fundamental to the pathogenesis of many cancers and other diseases. Despite many published works showing the diagnostic and prognostic potential of this approach, a number of factors that may influence the stable isotopic composition of these essential mineral elements in healthy individuals remain unstudied. In this perspective article, we summarize the available evidence from studies of archaeology, anthropology, ecology, animal models, and living humans relating to physiological and lifestyle factors that appear likely (there is evidence indicating their influence) or unlikely (there is evidence indicating their lack of influence) to require controlling for when investigating variations in essential mineral element isotopic compositions in human subjects. We also discuss factors that require additional data to properly assess. There is evidence that sex, menopausal status, age, diet, vitamin and metal supplementation, genetic variation, and obesity influence the isotopic composition of at least one essential metal in the human body. The task of investigating potential influences on essential mineral element isotopic compositions in the human body is sizeable, but presents an exciting research opportunity, with each incremental advance helping to improve the quality of research output in the context of isotope metallomics.
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The effect of coffee on contralateral suppression of transient evoked otoacoustic emissions
Article
Full-text available
  • Aug 2022
Background : Coffee is a popular non-alcoholic beverage consumed by humans across the world. It contains caffeine, which is a type of stimulant of the central nervous system. In the auditory system, it has a positive effect on auditory brainstem response and perception of speech in noise. Further, caffeine has an inhibitory effect in the cochlea, but studies have rarely investigated its effect on otoacoustic emissions (OAEs) in humans. OAEs are low-intensity sounds produced by the cochlea, which could be recorded in the ear canal. The present study was carried out to investigate the effect of coffee on transient evoked otoacoustic emission (TEOAE) and contralateral suppression of TEOAE. Method : A total of 52 young adults participated in the study. A cross-over study design was used for the present investigation. The TEOAE and contralateral suppression of TEOAE were recorded before and after consumption of coffee and milk. The contralateral suppression of TEOAE was measured by presenting white noise to the contralateral ear at 40, 50, and 60 dB sound pressure level (SPL). Results : The mean amplitude of TEOAE before and after consumption of coffee was similar in both ears. Further, the mean contralateral suppression of TEOAE was slightly larger after consumption of coffee in both ears. However, the mean difference was not significant in both the ears. Conclusions : Based on the findings of present study, coffee has no significant effect on the amplitude of TEOAE and contralateral suppression of TEOAE.
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Effect of caffeine on human health
Article
Full-text available
  • Jan 2003
Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is found in common beverages (coffee, tea, soft drinks), in products containing cocoa or chocolate, and in medications. Because of its wide consumption at different levels by most segments of the population, the public and the scientific community have expressed interest in the potential for caffeine to produce adverse effects on human health. The possibility that caffeine ingestion adversely affects human health was investigated based on reviews of (primarily) published human studies obtained through a comprehensive literature search. Based on the data reviewed, it is concluded that for the healthy adult population, moderate daily caffeine intake at a dose level up to 400 mg day(-1) (equivalent to 6 mg kg(-1) body weight day(-1) in a 65-kg person) is not associated with adverse effects such as general toxicity, cardiovascular effects, effects on bone status and calcium balance (with consumption of adequate calcium), changes in adult behaviour, increased incidence of cancer and effects on male fertility. The data also show that reproductive-aged women and children are 'at risk' subgroups who may require specific advice on moderating their caffeine intake. Based on available evidence, it is suggested that reproductive-aged women should consume </=300 mg caffeine per day (equivalent to 4.6 mg kg(-1) bw day(-1) for a 65-kg person) while children should consume </=2.5 mg kg(-1) bw day(-1).
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Dietary Animal and Plant Protein and Human Bone Health: A Whole Foods Approach
Article
Full-text available
  • Apr 2003
Urinary calcium excretion is strongly related to net renal acid excretion. The catabolism of dietary protein generates ammonium ion and sulfates from sulfur-containing amino acids. Bone citrate and carbonate are mobilized to neutralize these acids, so urinary calcium increases when dietary protein increases. Common plant proteins such as soy, corn, wheat and rice have similar total S per g of protein as eggs, milk and muscle from meat, poultry and fish. Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium. The effects of a protein on urinary calcium and bone metabolism are modified by other nutrients found in that protein food source. For example, the high amount of calcium in milk compensates for urinary calcium losses generated by milk protein. Similarly, the high potassium levels of plant protein foods, such as legumes and grains, will decrease urinary calcium. The hypocalciuric effect of the high phosphate associated with the amino acids of meat at least partially offsets the hypercalciuric effect of the protein. Other food and dietary constituents such as vitamin D, isoflavones in soy, caffeine and added salt also have effects on bone health. Many of these other components are considered in the potential renal acid load of a food or diet, which predicts its effect on urinary acid and thus calcium. "Excess" dietary protein from either animal or plant proteins may be detrimental to bone health, but its effect will be modified by other nutrients in the food and total diet.
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The association between smoking, beverage consumption, diet and bladder cancer: a systematic literature review
Article
Full-text available
  • Feb 2004
In this paper the association between smoking history, beverage consumption, diet and bladder cancer incidence is systematically reviewed. A rating system has been used to summarise the level of scientific evidence (i.e. convincing, probable, possible, and no evidence) and the level of association (i.e. substantially increased, (RR> or =2.5), moderately increased (1.5< or =RR<2.5), slightly increased (1.2< or =RR<1.5), no association (0.8< or =RR<1.2), slightly decreased (0.7< or =RR<0.8), moderately decreased (0.4< or =RR<0.7), and substantially decreased (RR<0.4)). There is convincing evidence that cigarette smoking status, frequency and duration substantially increase the risk of bladder cancer. However, the evidence is not clear for other forms of smoking. A small increased risk for cigar, pipe, and environmental smoking is only possible. There is possible evidence that total fluid intake is not associated with bladder cancer. Although there is convincing evidence for a positive association between alcohol consumption and bladder cancer risk in men, the risk is small and not clinically relevant. Coffee and tea consumption are probably not associated with bladder cancer. The authors conclude that total fruit consumption is probably associated with a small decrease in risk. There is probably no association between total vegetable intake, vitamin A intake, vitamin C intake and bladder cancer and a possibly moderate inverse association with vitamin E intake. Folate is possibly not associated with bladder cancer. There probably is a moderate inverse association between selenium intake and bladder cancer risk.
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Dietary animal and plant protein and human bone health: A whole foods approach
Conference Paper
  • Mar 2003
Urinary calcium excretion is strongly related to net renal acid excretion. The catabolism of dietary protein generates ammonium ion and sulfates from sulfur-containing amino acids. Bone citrate and carbonate are mobilized to neutralize these acids, so urinary calcium increases when dietary protein increases. Common plant proteins such as soy, corn, wheat and rice have similar total S per g of protein as eggs, milk and muscle from meat, poultry and fish. Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium. The effects of a protein on urinary calcium and bone metabolism are modified by other nutrients found in that protein food source. For example, the high amount of calcium in milk compensates for urinary calcium losses generated by milk protein. Similarly, the high potassium levels of plant protein foods, such as legumes and grains, will decrease urinary calcium. The hypocalciuric effect of the high phosphate associated with the amino acids of meat at least partially offsets the hypercalciuric effect of the protein. Other food and dietary constituents such as vitamin D, isoflavones in soy, caffeine and added salt also have effects on bone health. Many of these other components are considered in the potential renal acid load of a food or diet, which predicts its effect on urinary acid and thus calcium. "Excess" dietary protein from either animal or plant proteins may be detrimental to bone health, but its effect will be modified by other nutrients in the food and total diet.
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Coffee and cancer
Article
Epidemiological studies on the relation between coffee consumption and cancer risk have been mainly focused on cancers of the urinary bladder, pancreas and colorectum. The relation between coffee and bladder cancer is controversial, despite a large number of studies published over the last three decades. In most studies, the risk tends to be higher in coffee drinkers than in those who do not drink coffee, but the excess risk is generally moderate and is neither dose- nor duration-related. Thus, a strong association between coffee drinking and bladder cancer can be excluded, although it is still unclear whether the weak association is causal or nonspecific and due to some bias or confounding. For pancreatic cancer, a possible association with coffee consumption has been postulated in a large case-control study published in 1981; since then, however, most studies have shown no substantial association, and overall evidence suggests that coffee is not materially related to pancreatic cancer risk. Overall evidence on the coffee-colorectal cancer relation suggests an inverse association, since most case-control studies found odds ratios below unity, particularly for colon cancer. The pattern of risk is less clear for cohort studies. A plausible biological explanation has been given in terms of coffee-related reduction of bile acids and neutral sterol secretion in the colon. For other cancer sites, including oral cavity, oesophagus, stomach, liver, breast, ovary, kidney and lymphoid neoplasms, the relation of coffee drinking with cancer risk has been less extensively investigated, but the evidence is largely reassuring.
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Teratogen update: Evaluation of the reproductive and developmental risks of caffeine
Article
  • Jul 2001
Caffeine is a methylated xanthine that acts as a mild central nervous system stimulant. It is present in many beverages, including coffee, tea, and colas, as well as chocolate. Caffeine constitutes 1-2% of roasted coffee beans, 3.5% of fresh tea leaves, and approximately 2% of mate leaves (Spiller, '84; Graham, '84a,b). Many over-the-counter medications, such as cold and allergy tablets, headache medicines, diuretics, and stimulants also contain caffeine, although they lead to relatively minimal intake (FDA, '86). In epidemiological studies, it is assumed that one cup of coffee contains < or =100 mg of caffeine, and soft drinks, such as colas, contain 10-50 mg of caffeine per 12-ounce serving. The per-capita consumption of caffeine from all sources is estimated to be about 3-7 mg/kg per day, or approximately 200 mg/day (Barone and Roberts, '96). Consumption of caffeinated beverages during pregnancy is quite common (Hill et al., '77) and is estimated to be approximately 144 mg/day, or 2.4 mg/kg for a 60-kg human (Morris and Weinstein, '81). However, pregnant women appear to consume slightly less than do other adults, approximately 1 mg/kg per day (Barone and Roberts, '96). This decrease may be interrelated with taste aversion (Hook, '76; Little, '82). The medical literature contains many varied references that appear to indicate that human adverse reproductive/developmental effects are produced by caffeine. If caffeine indeed causes such effects, the reproductive consequences could be very serious because caffeine-containing foods and beverages are consumed by most of the human populations of the world, and consumption in the United States is estimated to be 4.5-kg/person/year (Narod et al., '91). Therefore, the medical literature dealing with developmental and reproductive risks of caffeine was reviewed, and the biological plausibility of the epidemiological and animal findings, as well as the methods and conclusions of previous investigators, were evaluated. The epidemiological studies describe exposures of women to caffeine during pregnancy, as well as the occurrence of congenital malformations, fetal growth retardation, small-for-date babies, miscarriages (spontaneous abortions), behavioral effects, and maternal fertility problems that presumably resulted from the caffeine consumption. A few epidemiological studies were concerned with the genetic effects of preconception exposures to caffeine. Animal studies, conducted mostly in pregnant rats and mice, were designed to produce malformations. The objectives of the present review are to summarize the findings from the various clinical and animals studies, objectively discuss the merits and/or faults inherent in the studies and establish a global reproductive risk assessment for caffeine consumption in humans during pregnancy. It should be noted that evaluation of the developmental risks of caffeine based solely on epidemiological studies is difficult because the findings are inconsistent. Even more important, is the fact that caffeine users are subject to multiple confounding factors that make analyses difficult and prevent investigators from reaching definitive conclusions. For example, the caffeine content of foods and beverages can vary considerably, which can interfere with obtaining valid interpretations from many human studies. Isolated epidemiological studies dealing with the risk of abortion, without evaluating other developmental and reproductive effects, are the most difficult to interpret, because they present special problems that are sometimes ignored in epidemiological studies. The results of animal studies are probably most helpful in solving some of the dilemmas created by the epidemiological studies. An animal study reported in 1960 first focused our attention on the potential developmental effects of caffeine. However, the exposure reported by Nishimura and Nakai ('60) was an intraperitoneal dosage of 250 mg/kg in the mouse, an extremely high dosage that would result in a blood plasma level that could never be obtained from consuming caffeine containing products. More recent animal studies have demonstrated, that depending on the method of administration and species, the developmental NOEL in rodents is approximately 30 mg/kg per day, the teratogenic NOEL is 8,100 mg/kg per day, and the reproductive NOEL approximately 80-120 mg/kg per day. Lack of biological plausibility to support the concept that caffeine has been responsible for human malformations is another important part of this analysis. For example, no one has described the Caffeine "teratogenic syndrome," a cluster of malformations associated with caffeine ingestion. Proven human teratogens have an identifiable syndrome. The malformations described in the animal studies at very high doses fit the description of vascular disruptive types of malformations. (ABSTRACT TRUNCATED)
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A review of the literature relating caffeine consumption by women to their risk of reproductive hazards
Article
From this detailed review of the literature, several conclusions can be drawn: (a) An association between caffeine consumption and a reproductive hazard is more likely to be seen in lower-quality studies than in studies that come closer to approximating the ideal. This is especially evident for "lower" birthweight and congenital anomalies. (b) The association between caffeine consumption and spontaneous abortion may well reflect the Stein-Susser epiphenomenon (women with prominent nausea tend to reduce caffeine consumption and nausea appears to be a marker of good implantation, perhaps reflecting a favorable balance of hormones produced by a healthy placenta). (c) The claim that caffeine consumption by women delays conception has not been followed by convincing support. (d) Reproductive hazards associated with cigarette smoking tend to be associated with caffeine/coffee consumption. Sometimes this appears to be a consequence of residual confounding associated with inadequate adjustment for cigarette smoking, which is over-represented among those who drink the most coffee/caffeine. Sometimes this reflects the tendency of women to underreport socially undesirable behaviors (e.g. smoking) while accurately reporting socially neutral behaviors (e.g. coffee and caffeine consumption). Thus, it seems reasonable to conclude that no convincing evidence has been presented to show that caffeine consumption increases the risk of any reproductive adversity.
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Coffee Consumption and Risk for Type 2 Diabetes Mellitus
Article
In small, short-term studies, acute administration of caffeine decreases insulin sensitivity and impairs glucose tolerance. To examine the long-term relationship between consumption of coffee and other caffeinated beverages and incidence of type 2 diabetes mellitus. Prospective cohort study. The Nurses' Health Study and Health Professionals' Follow-up Study. The authors followed 41 934 men from 1986 to 1998 and 84 276 women from 1980 to 1998. These participants did not have diabetes, cancer, or cardiovascular disease at baseline. Coffee consumption was assessed every 2 to 4 years through validated questionnaires. The authors documented 1333 new cases of type 2 diabetes in men and 4085 new cases in women. The authors found an inverse association between coffee intake and type 2 diabetes after adjustment for age, body mass index, and other risk factors. The multivariate relative risks for diabetes according to regular coffee consumption categories (0, <1, 1 to 3, 4 to 5, or > or =6 cups per day) in men were 1.00, 0.98, 0.93, 0.71, and 0.46 (95% CI, 0.26 to 0.82; P = 0.007 for trend), respectively. The corresponding multivariate relative risks in women were 1.00, 1.16, 0.99, 0.70, and 0.71 (CI, 0.56 to 0.89; P < 0.001 for trend), respectively. For decaffeinated coffee, the multivariate relative risks comparing persons who drank 4 cups or more per day with nondrinkers were 0.74 (CI, 0.48 to 1.12) for men and 0.85 (CI, 0.61 to 1.17) for women. Total caffeine intake from coffee and other sources was associated with a statistically significantly lower risk for diabetes in both men and women. These data suggest that long-term coffee consumption is associated with a statistically significantly lower risk for type 2 diabetes.
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