April 30, 2004 -- Soda-drinking teens -- especially black teens
April 30, 2004 -- Soda-drinking teens -- especially black teens -- are pushing their blood pressure dangerously high, according to new research.
"For adolescents, especially African-American adolescents, caffeine intake may increase blood pressure and thereby increase the risk of hypertension," writes researcher Margaret R. Savoca, PhD, with the Medical College of Georgia in Augusta. Other dietary and lifestyle practices may also play into this picture.
Caffeine is a risk factor for high blood pressure and heart disease. Adults primarily get caffeine from coffee, but in teens caffeinated soft drinks is the major source, writes the author.
Her study appears in the Archives of Pediatric and Adolescent Medicine.
Nearly three-quarters of teens -- 68% -- drink at least one soft drink daily, she reports. Up to 22% of teens also drink coffee and tea on a daily basis. Twice as many teens prefer caffeinated soft drinks to non-caffeinated.
The sugar content of soft drinks, and its contribution to the world's obesity problem, has received much attention. But little research has looked at the effects of caffeine content, writes Savoca.
Her study involved 159 black and white boys and girls about 16 years old. During the three-day study, each ate a special low-sodium diet that was prepackaged for them so study results wouldn't be skewed.
Researchers calculated the caffeine content in the foods (like chocolate) and beverages that each teen chose from meals they had selected. They also tested the kids' blood pressure before and during the study.
A 12-ounce regular cola contains 37 mg of caffeine, notes Savoca. Based on the quantity of caffeine consumed daily, the participants were divided into three groups: those that consumed less than 50 mg of caffeine per day, 50-100 mg of caffeine per day, and more than 100 mg of caffeine per day.
At the study's end, those teens who drank the amount of caffeine found in three or fewer sodas daily had relatively normal blood pressure readings, she reports.
The biggest difference was among black teens:
- Those drinking close to four or more sodas daily (greater than 100 mg of caffeine per day) had a six-point higher systolic blood pressure reading than white teens drinking the same amount of soda. (Systolic blood pressure is the top blood pressure number.)
- In black teens that drank more than 100 mg per day, the average systolic blood pressure was close to 120. A systolic blood pressure of 120 or more is considered prehypertension.
Diastolic blood pressure (the bottom number) was not significantly affected in any of the teens in her study, Savoca notes.
Why would lesser amounts of caffeine (less than 100 mg per day) have little effect on blood pressure? It could be due to differences in the metabolism of caffeine, which can vary between individuals and/or the body's adaptation to habitual use, writes Sarah C. Couch, PhD, RD, with Cincinnati Children's Hospital Medical Center, in an editorial accompanying the study.
Genetic predisposition -- as well other unhealthy diet and lifestyle habits -- could account for the black teens' higher blood pressure readings, Couch adds.
