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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 guaraná, 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.
(The following list is comprehensive, although not necessarily exhaustive. Contact your health care professional for more information.)
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.
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.
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
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.
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).
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.
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3. Gong H, Simmons MS, Tashkin DP, et al. Bronchodilator effects of caffeine in coffee. Chest 1986;89:335–42.
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11. Bruce M, et al. Anxiogenic effects of caffeine in patients with anxiety disorders. Arch Gen Psychiatry 1992;49:867–9.
12. Urgert R, Schulz AGM, Katan MB. Effects of cafestol and kahweol from coffee grounds on serum lipids and serum liver enzymes in humans. Am J Clin Nutr 1995;61:149–54.
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33. Pehl C, Pfeiffer A, Wendl B, Kaess H. The effect of decaffeination of coffee on gastro-oesophageal reflux in patients with reflux disease. Aliment Pharmacol Ther 1997;11:483–6.
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38. Stolzenberg-Solomon RZ, Miller ER 3rd, Maguire MG, et al. Association of dietary protein intake and coffee consumption with serum homocysteine concentrations in an older population. Am J Clin Nutr 1999;69:467–75.
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