How to safely enjoy caffeine

Caffeine is the stimulant in coffee, tea, chocolate and cola. It is also added to some painkillers, cold medications and weight-loss supplements. Caffeine speeds the heart rate, stimulates the central nervous system, increases urine flow and the production of digestive acids, and relaxes the muscles that control blood vessels and airways. Here are some tips on enjoying caffeine safely.

• Although caffeine in moderation is harmless, sudden withdrawal can cause headaches, irritability and other symptoms.
• In people who are sensitive to caffeine, it can trigger migraine headaches, while in others it might actually abort a migraine by relaxing the constricted blood vessels that are causing the pain.
• People with some types of heart disease are often advised to forgo caffeine; it can provoke palpitations or other cardiac arrhythmias.

• Caffeine increases mental alertness and the ability to concentrate.
• For many people a cup of coffee helps them get going in the morning, and coffee or tea breaks during the day give them a boost.
• Athletes have long observed that caffeine an hour before competition can temporarily improve performance, especially in endurance sports like distance running.
• Studies confirm that 250 milligrams of caffeine — the amount in two mugs of strong coffee — increases endurance, presumably because caffeine increases the body's ability to burn fat for fuel. However, high doses can also cause side effects and athletes must be aware of their individual tolerance.
• Caffeine may abort an asthma attack by relaxing constricted bronchial muscles.

• Caffeine late in the day can wreck your sleep, and excessive intake can lead to caffeinism, a syndrome marked by insomnia, anxiety and irritability, rapid heartbeat, tremors and excessive urination.
• Symptoms abate with the gradual withdrawal of caffeine.
• Caffeine is relatively nontoxic; one would have to quickly consume the amount found in 80 to 100 cups of coffee for a fatal adult dose.
• Because caffeine, especially in coffee, increases the production of stomach acid, ulcer patients are often advised to limit coffee (including decaffeinated) consumption to one cup after a meal. Many ulcer patients can tolerate tea, however.
• Caffeine can prompt a slight temporary blood pressure rise; it also speeds up the heart rate. For most heart patients, moderation is key — cardiologists generally advise no more than 400 to 450 mg of caffeine per day.
• Older people with hypertension should likely stick to one cup per day.
• Some studies suggest that drinking one or two cups of coffee each day during pregnancy brings a slightly increased risk of miscarriage and low-birth-weight babies, but others do not.
• There is stronger evidence that lots of daily caffeine during pregnancy may increase risk of a miscarriage, preterm delivery or low-birth-weight babies. Some experts suggest that pregnant women avoid coffee while others recommend limiting their daily caffeine consumption to 150 milligrams — or about one-and-a-half cups of coffee — spread over the day.
• Because caffeine enters breast milk, nursing mothers should either skip caffeinated beverages or drink them at least three hours before breastfeeding.
• Caffeine can in­crease the risk of osteo­porosis. Heavy coffee drinkers should consume more milk, yogourt and other high-calcium foods, or consider calcium supplements.
• Some people prefer decaffeinated coffee but worry about undesirable additives. But no: green coffee beans are soaked in water to extract the caffeine, and the solution is treated with a solvent in which caffeine is soluble. The solvent never touches the beans.