July 01 2005 12:00 AM EST
November 17 2015 6:13 AM EST
The topic of caffeine can lead to a stimulating conversation. While you are enjoying your tea or java, you should know some of the effects this can have on you and your health. The effects of a jolt of caffeine once in a while can be more noticeable than if you consume caffeine routinely, since you develop tolerance over time. After drinking or eating something with caffeine it might take 15 minutes to two hours to feel the effect as its concentration reaches peak level in your bloodstream. Caffeine affects both the central nervous system and skeletal muscle. It can increase heart and respiration rates and cause constriction of blood vessels, raising blood pressure. It has been used to increase the force of muscle contraction and reduce muscle fatigue. Caffeine is processed by the liver, and its 'half-life,' or how long it hangs around at its highest level in the body, is around three to seven hours. This time period is prolonged if you are pregnant or a smoker, making the effect last longer, even up to 18 hours. It also lasts longer in cases of liver disease. If you have any sleep disturbances, a fairly common issue for people with HIV infection, caffeine can make it worse. In a study of 44 patients who reduced their intake of caffeine by 90% for more than 30 days, sleep quality improved. And while caffeine is quite stimulating, it can relax the sphincter responsible for keeping food and such in your stomach from returning into your esophagus to cause heartburn (called reflux). In addition, it can increase acid production in the stomach, making that reflux especially painful. Caffeine can cause the gastrointestinal tract to move things through faster. If you have a tendency to have diarrhea, caffeine can make that worse. On other fronts, caffeine has also been implicated in the breakdown of body fat and glycogen, both important to stamina and energy level. Caffeine can also inhibit the absorption of dietary iron. A therapeutic dose of caffeine is about 200 milligrams, which is easily obtained from food and beverage consumption. A two-ounce espresso or a five-ounce cuppa (drip brewed) will give you 100 to 150 milligrams, and that frappuccino from Starbucks will provide around 80 milligrams. Even coffee ice cream and coffee yogurt can provide between 30 and 60 milligrams of caffeine. The amount you get from a cup of tea depends on how long it is brewed. A one-minute brew can provide 10 to 30 milligrams, and a five-minute brew pumps it up to 50 milligrams. Both regular and diet soft drinks can provide caffeine, ranging from more than 70 milligrams for a 12-ounce Jolt cola to between 40 and 55 milligrams for most other colas and even some noncola soft drinks, such as Mountain Dew and Mr. Pibb. If you are looking to decrease your caffeine intake from sodas, you can choose root beers, lemon-lime sodas, or caffeine-free colas. Chocolate can be a source of dietary caffeine, and the dark chocolate varieties have more of the stuff than the milk chocolate products (five to 60 milligrams per ounce for dark chocolate compared to one to 15 milligrams per ounce for milk chocolate). While caffeine does not appear to significantly interfere with medications, it may be worthwhile to look at your caffeine consumption and in some cases to make the choices to reduce your intake. Sit down with your dietitian and take a look at your diet and see where you can trim your caffeine intake, especially if you smoke or have problems with sleeping, diarrhea, heartburn, cardiovascular disease, dietary iron intake or related anemia, or liver disease. Fields-Gardner is the director of services for the Cutting Edge, an HIV nutrition company in the Chicago area. She is a member of the International AIDS Society and the American Dietetic Association's Dietetic Practice Group on HIV and AIDS. She has written a book on HIV medications and a guide to nutritional management of HIV for clinicians.