Health benefits and concerns

Alcohol withdrawal

While the support for dietary intervention remains somewhat unclear, many doctors suggest that alcoholics avoid caffeine. Two trials have shown that a diet that, among other changes, excludes caffeine, reduces the craving for alcohol.

Angina

Coffee should probably be avoided. Drinking five cups or more per day has been shown to increase the risk of angina, although effects of different forms of coffee on angina are unclear.

Anxiety

All sources of caffeine should be avoided, including coffee, tea, chocolate, caffeinated sodas, and caffeine-containing medications. People with high levels of anxiety appear to be more susceptible to the actions of caffeine.

Age-related cognitive decline

Caffeine may improve cognitive performance. One trial found that higher levels of coffee consumption were associated with improved cognitive performance, more so in older people than in younger people. Similar but weaker associations were found for tea consumption.

Atherosclerosis

Blood levels of an amino acid called homocysteine have been linked to atherosclerosis and heart disease. Most studies suggest that coffee drinkers have higher homocysteine levels than people who do not drink coffee. If coffee drinking does increase blood levels of homocysteine, the problem might be caused by chemicals in coffee that are trapped in paper filters. If so, paper-filtered coffee may not have this deleterious effect. Consumption of coffee made without paper filters will also raise cholesterol levels. Paper-filtered coffee does not have this effect.

Athletic performance

Caffeine is present in many popular beverages and appears to have an effect on fat utilization. While most trials show that caffeine does not benefit short-term, high-intensity exercise, some research has shown that endurance performance is enhanced by caffeine in many athletes. Caffeine consumption is banned by the International Olympic Committee at levels that produce urinary concentrations of 12 mg/ml or more. These levels would require ingestion of considerably more than 2.5mg per pound of body weight, or several cups of coffee over a short period of time.

Cancer (Bladder)

Most, but not all, published reports have shown coffee drinkers are at increased risk of bladder cancer. A review of 35 trials found a small (7%) increased risk of bladder cancer in coffee drinkers compared with people not drinking coffee––a difference that might have been due to chance.

Cancer (Breast)

Coffee drinking has been reported to increase breast pain associated with noncancerous lumps in the breast—a condition commonly called fibrocystic breast disease; some researchers believe some forms of fibrocystic breast disease increase the risk of breast cancer. However, coffee drinkers are at no higher risk of breast cancer than are women who do not drink coffee. Women wishing to reduce their risk of breast cancer do not need to avoid drinking coffee.

Cancer (Colon)

Some researchers believe that coffee drinking might reduce the risks of colon and rectal cancers by decreasing the intestinal level of secondary bile acids—substances in the gut that may increase the risk of these types of cancer. However, due to inconsistent support, the association between coffee drinking and protection against colon or rectal cancers remains unproven.

Cancer (Pancreatic)

While the relationship between coffee drinking and pancreatic cancer remains unclear, most scientists now believe drinking two cups of coffee per day or less will not increase the risk of pancreatic cancer.

Cardiac arrhythmia

Some studies have shown a connection between caffeine and cardiac arrhythmia. Although this effect is thought to be unlikely at moderate amounts, some healthy people appear to be susceptible to as little as one cup of coffee.

Depression

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.

Diarrhea

Drinking several cups of coffee per day causes diarrhea in some people. People with chronic diarrhea who drink coffee should avoid all coffee for a few days to evaluate whether coffee is the culprit.

Eczema

It has been reported that when heavy coffee drinkers with eczema avoided coffee, eczema symptoms improved. 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 to investigate food allergies should avoid coffee as part of this trial.

Endometriosis

While some research suggests that women who consume more than 5 grams of caffeine per month (about 1.5 cups of coffee a day) are more likely to have endometriosis, no study has investigated whether avoiding caffeine improves the symptoms of endometriosis.

Fibrocystic breast disease

Long-term and complete avoidance of caffeine reduces symptoms of what is commonly called fibrocystic breast disease. The decrease in breast tenderness can take six months or more to occur after caffeine is eliminated. Breast lumpiness has been reported to not respond well to avoidance of caffeine, but the pain decreases significantly in some women.

Gallstones

Caffeine increases bile flow and therefore might reduce the risk of gallstones––an effect supported by a study showing that coffee drinkers have a lower risk of gallstones than people who do not drink coffee. As caffeinated coffee can exacerbate symptoms of insomnia, peptic ulcer, panic attacks, and a variety of other conditions, people at risk for gallstones who wish to consider increasing coffee drinking to reduce risks should talk with a doctor beforehand.

Gastritis

Both regular and decaffeinated coffee increase stomach acid. Avoiding these substances should therefore aid in the healing of gastritis.

Gastroesophageal reflux disease (GERD)

Coffee drinking has been linked to increased heartburn pain.

Heart attack

Some but not all studies report that coffee drinking is associated with an increased risk of suffering a heart attack. This association may result from the ability of coffee to increase blood levels of homocysteine, or in the case of unfiltered coffee, to increase blood levels of cholesterol.

High cholesterol

Drinking boiled or French press coffee increases cholesterol levels. Modern paper coffee filters trap the chemicals in coffee that elevate cholesterol levels, keeping them from entering the cup. Therefore, drinking paper-filtered coffee generally does not increase cholesterol levels. However, paper-filtered coffee has been reported to significantly increase homocysteine—another risk factor for heart disease. The effects of decaffeinated coffee on cholesterol levels remain in debate.

High homocysteine

Coffee consumption has been associated with increased homocysteine levels, a risk factor for heart disease. These findings are consistent with studies that have found caffeine consumption to be associated with an increased risk of cardiovascular disease

High triglycerides

In a study of heavy caffeine users (people who were consuming an average of 560mg of caffeine per day from coffee and tea), changing to decaffeinated coffee and eliminating all other caffeinated products for two weeks resulted in a 25% reduction in triglyceride levels, a risk factor for heart disease.

Hypertension

Right after consuming caffeine from coffee or tea, blood pressure increases briefly. While the effects of long-term avoidance of caffeine (from coffee, tea, chocolate, cola drinks, and some medications) on blood pressure remain unclear, many doctors tell people with high blood pressure to avoid caffeine.

Hypoglycemia

Even modest amounts of caffeine have been reported to increase symptoms of hypoglycemia. For this reason, people with low blood sugar should avoid caffeinated beverages, including coffee.

Female infertility

Some but not all studies find that caffeine reduces female fertility. Many doctors recommend that women trying to get pregnant avoid caffeine.

Insomnia

The effects of caffeine—a stimulant—can last up to 20 hours, so some people will have disturbed sleep patterns even when their last cup of coffee was in the morning.

Iron-deficiency anemia

Coffee interferes with the absorption of iron. However, moderate intake of coffee (4 cups per day) may not increase the risk of iron-deficiency anemia if the diet contains adequate amounts of iron and vitamin C.

Kidney stones

While many doctors are concerned about the possible negative effects of caffeine consumption in people with a history of kidney stones, most current research suggests that it is not important for kidney stone formers to avoid coffee or tea. Preliminary studies in both men and women have found that coffee and tea consumption is actually associated with a reduced risk of forming a kidney stone. These reports suggest that the helpful effect of consuming more water by drinking coffee or tea may compensate for the theoretically harmful effect that caffeine has in elevating urinary calcium.

Osteoporosis

Caffeine increases urinary loss of calcium. Caffeine intake has been linked to increased risk of hip fractures and to a lower bone mass in women who consumed inadequate calcium. Many doctors recommend decreasing caffeinated coffee, black tea, and caffeine-containing soft drinks as a way to improve bone mass.

Parkinson’s disease

Some but not all research has found that higher coffee and caffeine intake is associated with a significantly lower incidence of Parkinson’s disease in older people. Until more is known, increasing caffeine consumption, even in people with a history of Parkinson’s disease in the family, is not recommended by doctors.

Peptic ulcer

Coffee (including decaf) can aggravate or interfere with the healing of peptic ulcers. People with peptic ulcer should avoid use of coffee—even decaf.

Pregnancy

Some but not all research links excessive caffeine consumption during pregnancy to growth-retardation, low birth weight, and spontaneous abortion. The United States Food and Drug Administration recommends that pregnant women should limit their caffeine intake to less than 400mg per day––the equivalent of less than four cups of coffee per day. Although some doctors suggest much lower levels of coffee consumption, no consensus has been reached on how much coffee drinking is safe for pregnant women.

Premenstrual syndrome

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. Moreover, the more caffeine women consumed, the more likely they were to suffer from PMS. A preliminary study showed that women with heavy caffeine consumption were more likely to have shorter menstrual periods and shorter cycle length compared with women who did not consume caffeine. Therefore, many doctors recommend that women with PMS avoid caffeine.

Rheumatoid arthritis

Drinking four or more cups of coffee per day has been associated with an increased risk of developing rheumatoid arthritis (specifically, the form that has a positive laboratory test for “rheumatoid factor”). Whether avoidance of coffee would reduce symptoms in people diagnosed with rheumatoid arthritis has yet to be investigated.