When the time changed this spring, I found myself drinking a lot more coffee, and I haven't stopped. Should I be concerned about caffeine?
It really depends what you mean by "a lot," but most authorities agree that if you're not feeling some obvious side-effects, the caffeine in coffee isn't a problem.
But a recent study on energy drinks supports previous research indicating that a lot of caffeine could increase your blood pressure and heart rate, at least temporarily. The researchers, reporting online in the Annals of Pharmacotherapy, tested 15 volunteers between the ages of 20 and 39 who drank two cans of energy drink within a half-hour once a day for seven days. Each can contained 100 milligrams of caffeine, as well as other substances, such as taurine and sugars, that could also have biological effects. (To compare, a 6-ounce cup of coffee can have 60 to 120 milligrams of caffeine, depending how it's brewed.) On the first and last days of the study, the researchers tested the subjects' blood pressure and heart rate and gave them electrocardiograms. The tests took place before they consumed the drinks and five times during the four hours afterward.
The electrocardiograms didn't change significantly, but the heart rate increased by 11 percent on day seven of the test, and the systolic blood pressure (the top number) increased 9.6 percent and diastolic blood pressure increased 7.8 percent.
While the study was a small one, the findings could be important for people who already have hypertension or heart disease. And, the researchers believe consumption of energy drinks could alter the effectiveness of some medications, so that could be important to know.
But other studies indicate regular caffeine consumption doesn't increase blood pressure, nor does eliminating caffeine appear to decrease blood pressure in regular caffeine consumers.
Everyone is different. Some people are more sensitive to caffeine than others. If you're concerned, the Mayo Clinic offers guidance in an article, "Caffeine: How much is too much?" online at http://www.mayoclinic.com/health/caffeine/NU00600. For example, if you find yourself suffering from insomnia, nervousness, restlessness, irritability, nausea, fast or irregular heartbeat, muscle tremors, headaches or anxiety, you may be getting too much caffeine -- time to cut back.
You may not even realize how much caffeine you're consuming, because it's rarely listed on the label. For a listing of foods highest in caffeine, go to http://www.nutritiondata.com and click on "Foods by Nutrient." Then you can search for foods and beverages that are highest in caffeine (it's near the bottom of the list). You might be surprised at what you find.
Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or firstname.lastname@example.org.
Editor: This column was reviewed by Julie Shertzer, registered dietitian and program specialist for Ohio State University Extension in the Department of Human Nutrition, in the College of Education and Human Ecology.