Q: I drink iced tea from morning until I go to bed at night. Does all that caffeine affect my blood pressure? Should I switch to decaf teas?
A: Caffeine is a stimulant and vasoconstrictor that can temporarily increase blood pressure even if you don’t have high blood pressure.
It is also thought that caffeine causes your adrenal glands to secrete more adrenaline causing the subsequent increase in blood pressure. Some researchers have found that caffeine increases blood pressure through adenosine receptor inhibition—blocking a hormone that keeps arteries dilated—along with a release of some neurotransmitters.
As it turns out, people who regularly drink caffeinated beverages are found to have a higher than average blood pressure than those who don’t. On the other hand, those who regularly drink coffees and teas develop a tolerance to the caffeine, which lowers its impact on blood pressure. These individuals are likely fast metabolizers of caffeine.
Those folks who are slow metabolizers of caffeine may present with high blood pressure after drinking a cup of joe or iced tea. For these people, it may be best to limit the amount of caffeine to less than 200 mg per day, which is about two eight-ounce cups of coffee, or just switch to decaffeinated. Make sure you get a Swiss process or water process decaf to avoid potentially harmful chemicals.
The best way to tell if all that iced tea you’re drinking is impacting you at all is to take your blood pressure before you drink your first glass, then again 30 minutes to two hours after. If it is higher, you’re likely a slow metabolizer of caffeine and should consider switching to decaffeinated iced tea.
My advice to those of you visiting the doctor today: skip that cup of java to get a true blood pressure reading. I’ve encountered too many patients dismayed at receiving a prescription for blood pressure medication that could have been avoided.
To your health!
Leyla Muedin, MS, RD, CDN
