Negative Effects of Caffeine
Most of the negative effects are not a concern with occasional caffeine use, such as a cup of coffee, tea, or cola a few times a week or even once daily. However, with regular use of over 100 mg. daily, many problems arise. A limit of one cup of coffee daily is suggested, along with a week off every few months just to assure us that we are not addicted and that we do not have appreciable symptoms from stopping or restarting. If we do, then we should stop totally.

The risks discussed in the following list vary with the level of caffeine intake. A total of over 500 mg. daily could be a relatively high intake. The total includes coffee, tea, soft drinks, and drugs (that is, five cups of coffee a day or a few cups of coffee and a few caffeinated aspirins, as examples). Between 250 and 500 mg. might be classified as moderate intake, while under 250 mg. would be low. With chronic use, the risks of problems rise, and even lower amounts become more of a concern.

For a long time, the popularity of caffeine has led people to resist the initial negative findings. Now the dangers are fairly clear, and it is hard to refute the evidence of the many difficulties generated by this addictive drug. Possible negative effects from caffeine use and abuse include the following:

• Common side effects of caffeine use include excess nervousness, irritability, insomnia, "restless legs," dizziness, and subsequent fatigue. Headaches can also be very common, as is "heartburn." Psychological symptoms of general anxiety or panic attacks may also occur. Hyperactivity and bed wetting may also develop in children who consume caffeine.

• An acid irritant to the gastrointestinal tract and liver, caffeine directly increases stomach hydrochloric acid production, so it is clearly bad for people with or prone to ulcers or gastritis. Regular coffee drinking thus also increases the likelihood of peptic ulcer disease. Decaffeinated coffee is also acidic, though it is less stimulating.

• Caffeine’s diuretic effect causes loss of potassium, magnesium, zinc and other minerals, and B vitamins, especially thiamine B1. Caffeine also washes out vitamin C. Therefore, all of these nutrients can be deficient unless they are obtained from foods in increased amounts or taken as supplements.

• Caffeine, and particularly coffee, reduces absorption of iron and calcium, especially when it is drunk around mealtime. These minerals are extremely important for women. Osteoporosis and anemia are thus more common with regular coffee use. Also in children and adolescents, caffeinated drinks interfere with these essential minerals needed for growth and health.

• Diarrhea can also occur with increased amounts of caffeine, which relaxes the smooth muscle in the colon. The laxative effect of caffeine can also create a dependency.

• A number of negative cardiovascular effects are caused by caffeine. First, it raises the blood pressure. Hypertension is a risk factor in atherosclerosis and heart disease. Caffeine increases cholesterol and triglyceride blood levels, also risk factors in cardiovascular disease. Heart rhythm disturbances, arrhythmias, though usually of a mild type, occur with caffeine; these include a generally increased heart rate (tachycardia) and excitability of the heart nerve conduction system, leading to both palpitations and extra beats. Caffeine also increases norepinephrine secretion, which causes some vasoconstriction—that is, restricted blood flow. Although caffeine may have a mild direct vasodilating effect in the heart and body (vasoconstricting in the brain), the adrenal stimulation may override this. Research reports regarding caffeine’s role in increasing the risk of heart attacks are mixed; however, it seems reasonable with the cardiovascular stimulation of caffeine to assume that drinking four to five cups of coffee per day does increase the incidence of myocardial infarctions. Overall, caffeine clearly increases risk of cardiovascular disease.