Caffeine & Coffee
Most but not all problems associated with coffee drinking result from the effects of caffeine. Caffeine is also found in black and green tea, most cola drinks, chocolate, cocoa, the herb guarana, and some over-the-counter drugs. Although caffeine content varies considerably, fresh brewed coffee typically contains more caffeine than instant coffee and vaguely twice as much as black tea, which in turn contains more caffeine than does green tea. Amounts of caffeine in chocolate and cocoa are significantly lower, and caffeine content of other groups of products varies greatly.
In addition to problems caused by coffee drinking, there may be a few benefits. Some,1 but not all2 studies suggest that coffee drinkers have a lower risk of colon cancer. Caffeine is known to dilate breathing passages3 and has been used as an acute treatment for asthmatic attack when other remedies are unavailable.4 In addition, athletic performance during enduranceexercise appears to be enhanced by caffeine in many athletes,5,6 and caffeine may reduce constipation.7 Coffee drinking has also been linked to reduced risk of suicide in women.8
Warning to pregnant women: Caffeine ingestion during pregnancy has been linked to growth-retardation or low birth weight in infants.9 The risk of spontaneous abortion is also higher in women who consume caffeine.10 Many nutritionally oriented doctors recommend that pregnant women limit their caffeine intake to a maximum of 300 mg (or approximately three cups of coffee) per day.
Health Problems Associated with Caffeine & Coffee
(The following list is comprehensive, although not necessarily exhaustive. Contact your health care professional for more information.)
Anxiety/Panic DisorderAnxiety describes feelings of worry or dread, usually about potential future events. All sources of caffeine--including coffee, tea, chocolate, cocoa, guarana, and some medications--should be avoided by those with anxiety or panic disorders. People with high levels of anxiety appear to be more susceptible to the actions of caffeine.11 Decaffeinated coffee, tea, and sodas do not contribute to anxiety.
Cholesterol (High)Although it is by no means the only major risk factor, elevated serum cholesterol is clearly associated with a high risk of heart disease. Drinking boiled or French press coffee increases cholesterol levels.12 Coffee made with paper filters does not increase cholesterol levels.13,14 The effects of decaffeinated coffee on cholesterol levels remain in debate.15
DepressionDepression, characterized by unhappy feelings of hopelessness, can be a response to stressful events, hormonal imbalances, biochemical abnormalities, or other causes. Restricting caffeine and sugar in people with depression has been reported to elevate mood in preliminary research.16 How much of this effect resulted from sugar and how much from caffeine remains unknown. Researchers have reported that psychiatric patients who are heavy coffee drinkers are more likely to be depressed than other such patients.17 However, whether caffeine caused depression or whether depressed people were more likely to want the "lift" associated with drinking a cup of coffee remains unclear. In fact, "improvement in mood" is considered an effect of long-term coffee consumption by some researchers, a concept supported by the fact that people who drink coffee have been reported to have a 58-66% decreased risk of committing suicide compared with non-coffee drinkers.18 Nonetheless, a symptom of caffeine addiction can be depression. Thus, consumption of caffeine (mostly from coffee) has paradoxically been linked with both improvement in mood and depression, by different researchers. People with depression may want to avoid caffeine, as well as sugar, for one week to see how it affects their mood.
DiabetesPeople with diabetes cannot properly process glucose, a sugar the body uses for energy. As a result, glucose stays in the blood, causing blood glucose levels to rise. At the same time, however, the cells of the body can be starved for glucose. Diabetes can lead to poor wound healing, higher risk of infections, and many other problems involving the eyes, kidneys, nerves, and heart. Preliminary research has linked coffee consumption in children to an increased risk of insulin dependent diabetes.19
DiarrheaDrinking several cups of coffee per day causes diarrhea in some people.20 People with chronic diarrhea who drink coffee should avoid all coffee for a few days to evaluate whether coffee is the culprit.
EczemaEczema is a common skin condition characterized by an itchy, red rash. One study reported that when heavy coffee drinkers with eczema avoided coffee, eczema symptoms improved.21 In this study, the reaction was to coffee--not caffeine, indicating that some people with eczema may be allergic to coffee. People with eczema who are using a hypoallergenic diet (with the guidance of a nutritionally oriented doctor) to investigate food allergies should avoid coffee as part of this trial.
Fibrocystic Breast DiseaseFibrocystic breast disease is a term colloquially given to a group of very common benign conditions affecting the breast in younger women. Both breasts become tender or painful and lumpy, and the symptoms vary at different times in the menstrual cycle.
Long-term and complete avoidance of caffeine reduces symptoms of fibrocystic breast disease.22,23 Caffeine is found in coffee, black and green tea, some soft drinks, chocolate, cocoa, and a number of over-the-counter drugs. The decrease in breast tenderness can take six months or more to occur after caffeine is eliminated. Breast lumpiness may not go away; however, the pain often decreases.
Many doctors are confused about the effects of caffeine on breast tissue, because at first glance, the research appears contradictory. When researchers tell women to cut back or to eliminate caffeine for less than six months, results are unimpressive.24,25 Moreover, for every study that says fibrocystic disease patients do not drink more coffee than other women,26,27 another study says otherwise.28,29 More important, the original research did not claim that fibrocystic patients drink much coffee--only that they are especially sensitive to the coffee they do drink.
Twins with similar or identical genes should be affected similarly by caffeine. Research has been done studying the effects of caffeine on breast symptoms in twins. In that report, the twin with symptoms was more likely be the coffee drinker.30 This evidence clearly supports the idea that coffee drinking can affect breast symptoms in some women.
GastritisGastritis is a broad term for inflammation of the lining of the stomach. This condition can be caused by many factors and, in some cases, may lead to an ulcer. Caffeine found in coffee, black and green tea, some soft drinks, chocolate, cocoa, and many medications increases stomach acid,31 though decaffeinated coffee does as well.32 Avoiding these substances aids in the healing of gastritis.
Gastroesophageal RefluxDrinking coffee can increase the risk of gastroesophageal reflux (the return of stomach contents back up into the esophagus). This frequently causes heartburn because of irritation of the esophagus by stomach acid. Decaffeinated coffee is less likely to cause reflux.33
Homocysteine (High)Homocysteine, a normal breakdown product of the essential amino acid methionine, is believed to exert a number of toxic effects in the body. A growing body of evidence suggests that an elevated homocysteine level is a risk factor for heart disease, independent of other known risk factors such as elevated serum cholesterol and hypertension,34,35 though, in some research the link has appeared only in women.36
Two studies have reported that coffee consumption is associated with increased homocysteine levels.37,38 These findings are consistent with studies that have found both smoking and caffeine consumption to be associated with an increased risk of both cardiovascular disease and osteoporosis.
HypertensionHypertension is the medical term for high blood pressure. The cause of most hypertension remains unknown. Shortly after consuming caffeine, blood pressure increases.39 In an analysis of eleven trials lasting almost two months on average, coffee drinking led to increased blood pressure, though these increases were typically small to moderate.40 Nonetheless, the effects of long-term avoidance of caffeine (from coffee, tea, chocolate, cocoa, some soft drinks, and some medications) on blood pressure remain unclear. In fact, a few reports claim that long-term coffee drinkers have lower blood pressure than those who avoid coffee.41 On the basis of the two-month intervention trials, many nutritionally oriented doctors tell people with high blood pressure to avoid caffeine-containing food and drink despite the lack of clarity in published research.
HypoglycemiaThe technical meaning of hypoglycemia is low blood sugar. Common symptoms are fatigue, anxiety, headaches, difficulty concentrating, sweaty palms, shakiness, excessive hunger, drowsiness, abdominal pain, and depression. In a preliminary report, some people with hypoglycemia were reported to improve when they eliminate sources of caffeine from their diet.42 Caffeine is found in regular coffee, black and green tea, some soft drinks, chocolate, cocoa, and many over-the-counter pharmaceuticals.
Infertility (Female)Caffeine consumption equivalent to more than two cups of coffee per day has been linked to fallopian tubal disease and endometriosis--both of which can cause female infertility.43 As little as one to one and a half cups of coffee per day appears to delay conception in women trying to get pregnant.44 Some studies have reported that one cup of coffee per day cut fertility in half,45 although others report that it takes two46 or three47 cups to have detrimental effects.
Caffeine is found in regular coffee, black and green tea, some soft drinks, chocolate, cocoa, and many over-the-counter pharmaceuticals. While not every study has found that caffeine reduces female fertility,48 most doctors of natural medicine recommend that women trying to get pregnant avoid caffeine. Decaffeinated coffee has been linked to spontaneous abortion.49 Some researchers suspect that the tannic acid found in any kind of coffee and black tea may contribute to infertility.50
InsomniaThe inability to get a good night's sleep can result from waking up in the middle of the night and having trouble getting back to sleep. It also occurs when people have a hard time getting to sleep in the first place. Insomnia can be a temporary, occasional, or chronic problem. Caffeine is a stimulant.51 The effects of caffeine can last up to twenty hours,52 so some people will have disturbed sleep patterns even when their last cup of coffee was in the morning. Besides regular coffee, black and green tea, cocoa, chocolate, some soft drinks, and many over-the-counter pharmaceuticals also contain caffeine.
Iron-Deficiency AnemiaAnemia is a reduction in the number of red blood cells (RBCs), in the amount of hemoglobin in those cells, and in another related index called "hematocrit." As opposed to all other common causes for anemia, iron-deficiency anemia also causes RBCs to be abnormally small. Since RBCs are needed to carry oxygen to tissues, anemia impairs oxygen supply to the body. Some common symptoms of anemia include fatigue, lethargy, weakness, poor concentration, and impaired immune function. In iron-deficiency anemia, fatigue also occurs because iron is needed to make optimal amounts of ATP--the energy source the body runs on.
Coffee interferes with the absorption of iron.53 However, moderate intake of coffee (four cups per day) may not adversely affect the risk of iron-deficiency anemia when the diet contains adequate amounts of iron and vitamin C.54 Black tea contains tannins that strongly inhibit the absorption of the most common form of dietary and supplemental iron (non-heme iron). In fact, this iron-blocking effect is so effective that drinking black tea can help treat hemochromatosis, a disease of iron overload.55 Consequently, individuals who are iron deficient should avoid drinking tea.
Morning GrogginessThe consumption of coffee (and other caffeinated beverages) can contribute to grogginess in the morning, a condition that is generally remedied by drinking coffee in the morning.56 Many nutritionally oriented doctors consider these effects symptomatic of an addiction to caffeine, suggesting that the best solution may be to remove caffeine from the diet permanently.
OsteoporosisPeople with osteoporosis have brittle bones, which increases the risk of bone fracture, particularly in the hip, spine, and wrist. Caffeine has been linked to fracture of the hip in a large study following American women for six years.57 Caffeine increases urinary loss of calcium.58 In one trial, caffeine was linked with lower bone mass but only in women who consumed relatively little calcium.59 The authors of this report concluded that two to three cups of coffee per day might speed bone loss in women with calcium intakes of less than 800 mg per day. Many nutritionally oriented doctors recommend decreasing caffeine intake from caffeinated coffee, black tea, and cola drinks as a way to improve bone mass.
In a group of 980 postmenopausal women, lifetime caffeine intake equal to two cups of coffee per day was associated with decreased bone density in those who did not drink at least one glass of milk daily during most of their life.60 However, in 138 healthy postmenopausal women, long-term dietary caffeine (coffee) intake did not associate with bone density.61 Until more is known, postmenopausal women should limit caffeine consumption and consume a total of approximately 1,500 mg of calcium per day (from diet and supplements).
Peptic UlcerPeptic ulcers are erosions in the stomach or duodenum (the first part of the small intestine). Caffeinated and decaffeinated coffee62,63 increase stomach acidity, which can interfere with the healing of an ulcer.
Premenstrual Syndrome (PMS)Many premenopausal women suffer from symptoms of premenstrual syndrome (PMS). These symptoms typically begin at the end of each monthly cycle and resolve with the start of menstruation. Specific problems--cramping, bloating, mood changes, and breast tenderness--vary from woman to woman.
In a study of Chinese women, increasing tea consumption was associated with increasing prevalence of PMS.64 Among a group of college students in the United States, consumption of caffeine-containing beverages was associated with increases in both the prevalence and severity of PMS.65 Moreover, the more caffeine women consumed, the more likely they were to suffer from PMS.66 Therefore, many nutritionally oriented doctors recommend that women with PMS avoid sources of caffeine.
1. Ekbom A. Substantial coffee consumption was associated with a lower risk of colorectal cancer in the general population. Gut 1999;44:597.