Caffeine boosts blood pressure in the short term, but habitual drinkers may not face the same risk. Researchers followed 155,594 American women over 12 years (from the ongoing Nurses Health Study) and found an inverted-J-shaped relation between high coffee intake and hypertension risk. Colas, however, demonstrated a linear correlation. Caffeinated soft drinks may harbor unidentified risk-boosting compounds, or perhaps the antioxidants in coffee protect the cardiovascular system.

Number in study who developed hypertension: 33,077

Number in the U.S. with hypertension: 50 million

Percent change in relative risk when the daily intake of coffee was:

Less than 1 cup: 0

1 cup: 6

2–3 cups: 0

4–5 cups: 7 to 9

6 or more cups: 9 to 12

Percent change when the daily intake of cola was:

Less than 1 cup: 0

1 cup: 9 to 13

2–3 cups: 11 to 24

4–5 cups: 28 to 44

SOURCE: Journal of the American Medical Association, Vol. 294; November 9, 2005. Data shown combine the results of two cohorts, which spanned slightly different periods.