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Hypertension & Caffeine

May 1, 2011 | By Beth Greenwood
Hypertension & Caffeine
Photo Credit Coffee And Tea image by Fotoskat from Fotolia.com

Caffeine is found in many foods, drinks and medicines. With tea, coffee or hot cocoa comes caffeine as does a chocolate bar and cola drinks. Caffeine is a drug, and like many drugs, it can affect blood pressure or hypertension. Learn how to control your caffeine intake so that you can positively affect your blood pressure.

About Caffeine

Caffeine is a colorless, bitter substance commonly used to help people stay awake or increase energy. A cup of brewed coffee can range from 40 to 180 mg for an 8 oz. cup, while cocoa is closer to 4 mg a cup. Soft drinks may contain from 36 to 90 mg/oz., while energy drinks usually have about the same amount of caffeine as a cup of coffee. Even decaffeinated coffee has caffeine---about 3 to 5 mg a cup. Caffeine is also found in both prescription and over the counter medicines.

Hypertension

To talk about hypertension, you first need to understand how blood pressure is measured. You may have heard a doctor or other health care professional say something like "your blood pressure is 120 over 80". The first number is the pressure on the arteries as the heart contracts; the second number is the pressure as the heart relaxes. The first is called the systolic blood pressure and the second the diastolic. High blood pressure or hypertension as defined by the Cleveland Clinic is a systolic over 140 or a diastolic over 90. Hypertension can be very dangerous, causing damage to the heart, brain, eyes and blood vessels. People with hypertension can have no symptoms; sometimes the first sign of hypertension is a stroke.

Research

Caffeine, according to Dr. Sheldon Sheps in the Mayo Clinic's Expert Answers, can cause a short but dramatic increase in blood pressure, even if you don't normally have blood pressure problems. Two to three cups of coffee, says Dr. Sheps, can increase your blood pressure by up to 14 mm of mercury, a considerable change. Exactly how this happens is unclear -- possibilities include changes in hormones or the caffeine may cause the adrenal glands to secrete more adrenalin, which increases blood pressure. The most common source of caffeine for most people is coffee. Coffee does increase blood pressure, according to a meta-analysis research study by Z. Zhang, et. al., published in the March 2011 "American Journal of Clinical Nutrition." Zhang reports that one to three cups of coffee a day slightly increased the risk of hypertension. Other research says the source of the caffeine may be the most important factor. A study that looked at data from the long-running Nurses' Health Study was reported in the November 2005 issue of the "Journal of the American Medical Association" by W. C. Winklemayer. Winklemayer's researchers found that cola drinks -- sugared or diet -- did increase blood pressure, but that coffee did not. Dr. Sheps also notes that a person can develop tolerance to caffeine, and even with regular intake of caffeine, blood pressure might not increase.

Additional Considerations

At this time, it's hard to be sure if caffeine always affects a patient with hypertension, or if the effects are negative. Dr. Sheps says to try checking your blood pressure about 30 minutes after you consume caffeine; a reading that is up by 5 to 10 points may indicate caffeine sensitivity. If that's the case, you could benefit from either cutting back or stopping caffeine entirely. Caffeine can cause withdrawal symptoms such as headache; it may be wise to taper off rather than stopping suddenly, especially if your caffeine intake is high. If you do have high blood pressure, or think you might, be sure to discuss any concerns with your health care professional.

References

Article reviewed by Jenna Marie Last updated on: May 1, 2011

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