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Caffeine’s effects on blood pressure have been widely studied, but all this research has not produced any widely accepted conclusions.

In a 2000 study of men, researchers investigated the effects of caffeine consumption on five groups – those with optimal blood pressure, normal pressure, high normal pressure, stage 1 high blood pressure, and men in treatment for high blood pressure at a hypertension clinic. Their blood pressure was measured after 20 minutes of rest and then again 45-60 minutes after ingesting 250 mg of caffeine. (A cup of brewed coffee contains approximately 100 mg of caffeine.)

The researchers found that caffeine did increase blood pressure on average, but not equally in all groups. While there was some increase in both systolic and diastolic blood pressure for men in the optimal and normal groups, the greatest increases were in the other three groups. In fact, those who were already in treatment for high blood pressure had the highest increases, almost 1.5 times greater than for those with optimal blood pressure. While the blood pressures of none of the men in the first two categories rose above 140/90 mm Hg (the hypertensive range), an increasing percentage in the other three categories did rise to that level: After caffeine ingestion, 19 percent of the high-normal, 15 percent of the stage 1, and 89 percent of the diagnosed hypertensive groups fell into the hypertensive range.

In a large study of women and caffeine, researchers found that the blood pressure readings of those who consumed little caffeine or a lot of caffeine were unaffected. Interestingly, those who consumed caffeinated colas, either diet or regular, did have modest increases in blood pressure. The increases were not significant enough that the researchers could recommend not drinking cola drinks.

Although caffeine may increase blood pressure temporarily, especially in people who are not habitual coffee or caffeinated-beverage drinkers, researchers have found no consistent evidence that average caffeine consumption (2-4 cups of brewed coffee per day) increases blood pressure to any significant degree for people who do not already have high blood pressure. The American Heart Association has concluded that there is no harm in the daily consumption of 1-2 cups of coffee or its equivalent.

There is no healthy level of high blood pressure. If your levels are above normal (less than 120 mm Hg systolic and less than 80 mm Hg diastolic), you should undertake lifestyle changes. Your doctor will decide whether to prescribe medications. Most people with high blood pressure require two or more medications to keep their blood pressure at goal.

Modifying your lifestyle and taking medication is not an either/or choice. Adopting a healthy lifestyle is critical for the prevention of high blood pressure and an indispensable part of managing it. Think of these changes as a “lifestyle prescription” and make every effort to comply with them. They aren’t optional!

Lifestyle modifications can reduce blood pressure, prevent or delay high blood pressure, enhance the effectiveness of blood pressure medications, and overall lower your risk of heart attack, heart disease and stroke.

Elements of the “lifestyle prescription”

• Weight control: Losing as few as 10 pounds reduces blood pressure and/or prevents hypertension in many overweight people (people with a Body Mass Index of 25 or greater), although the ideal is to maintain normal body weight. Learn more about managing your weight.
• Diet: Healthy eating also improves blood pressure. In particular the DASH (Dietary Approaches to Stop Hypertension) eating plan has proven effective and easy to follow. The DASH diet emphasizes fruits, vegetables, fat-free or low-fat milk and milk products, whole grain foods, fish, poultry, beans, seeds and nuts. It also contains less salt and sodium, sweets, added sugars and sugar-containing beverages, fats and red meat than the typical American diet. According to one study, it reduced systolic and diastolic blood pressure by 5.5 and 3.0 mm Hg compared to the control diet (what the average American eats). Learn more about diet and nutrition.
• Salt: Healthy people should limit sodium to 2,300 mg or less (about 1 teaspoon) per day. African Americans, middle-aged and older adults and people with high blood pressure need less than 1,500 mg (about 2/3 of a teaspoon) per day. Remember, the majority of sodium typically comes from processed food, not salt added at the table. Learn more about reducing sodium.
• Physical Activity: Engage in regular moderately strenuous physical activity such as brisk walking at least 30 minutes per day most days of the week. Learn more about physical activity and fitness.
• Alcohol: If you drink, limit yourself to no more than two drinks per day for men and no more than one drink per day for women. One drink equals one 12-ounce beer, one ounce of hard liquor or one 5-ounce glass of wine. Learn more about alcohol and cardiovascular disease.
• Tobacco: Avoid all forms of tobacco as well as secondhand smoke. Learn how to quit smoking.

Your doctor will work with you on a plan to monitor your blood pressure while you follow your treatment plan. The American Heart Association recommends home monitoring for all people with high blood pressure to help your doctor determine whether your treatment is working. It’s not possible to make a one-size-fits-all rule about when to begin taking medication. This is a decision for you and your doctor to make. Factors he or she will consider are your age, body mass index, activity level and blood pressure numbers. As reluctant as you may be to take a prescription, the effects of high blood pressure are serious. And those effects are cumulative, so the sooner you begin counteracting them, the better.

High blood pressure is a chronic condition and the damage it causes to blood vessels and organs generally occurs over years. However, it is possible for blood pressure to rise quickly and severely enough to be considered a medical emergency requiring immediate treatment at a hospital.

Extremely high blood pressure – anything above 180/110 mm Hg – is called a hypertensive crisis. In addition to extremely high blood pressure, a person having such a crisis may experience one or more of these signs or symptoms:

• Severe headache
• Severe anxiety
• Shortness of breath

The consequences of uncontrolled blood pressure in this range can be severe and include:

• Stroke
• Loss of consciousness
• Memory loss
• Heart attack
• Damage to the eyes and kidneys
• Blood vessel damage
• Aortic dissection
• Angina (unstable chest pain)
• Fluid backup in the lungs
• Loss of kidney function

A hypertensive crisis can cause blood vessels to become inflamed and potentially leak blood, making it difficult to maintain adequate blood circulation. Inadequate circulation can cause organ damage and failure.

A spike in blood pressure of this magnitude is a medical emergency, and the person experiencing it should be hospitalized immediately. There is no safe duration for blood pressure to remain in this range. Do not wait to see if your pressure comes down on its own. Call 9-1-1 immediately for emergency medical assistance. If you can’t access the emergency medical services (EMS), have someone drive you to the hospital right away. If you’re the one having symptoms, don’t drive yourself, unless you have absolutely no other option.

Stress definitely affects our bodies. In addition to the emotional discomfort we feel when faced with a stressful situation, our bodies react by releasing stress hormones (adrenaline and cortisol) into the blood. These hormones prepare the body for the “fight or flight response” by making the heart beat faster and constricting blood vessels to get more blood to the core of the body instead of the extremities. Constriction of blood vessels and increase in heart rate does raise blood pressure, but only temporarily – when the stress reaction goes away, blood pressure returns to its pre-stress level. This is called situational stress, and its effects are generally short-lived and disappear when the stressful event is over.

“Fight or flight” is a valuable response when we are faced with an imminent threat that we can handle by confronting or fleeing. However, our modern world contains many stressful events that we can’t handle with those options. Chronic (constant) stress causes our bodies to go into high gear on and off for days or weeks at a time. The links between chronic stress and blood pressure are not clear.

This kind of stress is a difficult concept to pin down and measure, which is one of the problems researchers run into when trying to answer the question about stress and high blood pressure. Without a universal definition of chronic stress, stress levels are hard to measure and responses to stress vary from person to person.

Stress, even chronic stress, does not cause high blood pressure. The fact is that experts don’t know what causes high blood pressure, but contributing factors include being overweight, eating a diet high in sodium, being physically inactive and drinking too much alcohol. And people who are under stress may be more likely to eat too much, drink too much alcohol and be less active.

So, how does stress affect blood pressure? Situational stress causes changes in the body – increased heart rate and blood vessel constriction – that increase blood pressure until the situation passes, at which time blood pressure returns to its previous level. On the other hand, chronic stress can affect behaviors such as over-eating unhealthy food, not taking time to exercise or relax or drinking too much alcohol that may, in turn, increase blood pressure.

In the early 1900s, it was assumed that headaches were more common among people with high blood pressure. However, research into the subject has debunked this view. The best evidence available today indicates that high blood pressure does not cause headaches. According to one study, just the opposite appears to be true – people with high blood pressure seem to have significantly fewer headaches than the general population.

In a study published in the journal Neurology, people with higher systolic blood pressure (the larger or top number in blood pressure readings) were up to 40 percent less likely to have headaches compared to those with healthier blood pressure readings. The researchers also looked at another measurement called the pulse pressure, which is the change in blood pressure when the heart contracts. Pulse pressure is calculated by subtracting the bottom number (diastolic reading) from the top number (systolic reading). Those with higher pulse pressure had up to 50 percent fewer headaches. The researchers think that the higher the pulse pressure, the stiffer the blood vessels. The stiffer the blood vessel, the less likely the nerve endings are working properly. If the nerve endings aren’t functioning correctly, the less likely you will feel pain.

Extremely high blood pressure (at the level considered a hypertensive crisis – 180/110 mm Hg) may be accompanied by a headache – or it may not. Blood pressure this high is a medical emergency, and the person experiencing it should be hospitalized immediately. There is no safe duration for blood pressure to remain in this range. Do not wait to see if blood pressure comes down on its own. Do not wait to see if other symptoms develop. Call 9-1-1 immediately for emergency medical assistance. If you can’t access the emergency medical services (EMS), have someone drive you to the hospital right away. If you’re the one having symptoms, don’t drive yourself, unless you have absolutely no other option.

Another important point: High blood pressure is a leading risk factor for stroke, and one of the five warning signs of stroke is sudden, severe headache with no known cause. The other signs are:

• Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• Sudden confusion, trouble speaking or understanding
• Sudden trouble seeing in one or both eyes
• Sudden trouble walking, dizziness, loss of balance or coordination

If you or someone with you has one or more of these symptoms, call 9-1-1 immediately for emergency medical assistance and tell the operator you think it’s a stroke. If you can’t access the emergency medical services (EMS), have someone drive you to the hospital right away.

High blood pressure itself does not have symptoms. The only way to tell if you have high blood pressure is for a doctor to diagnose it after a period of monitoring.